PM_X-1 0.0.1: Pimoroni Explorer sibling firmware + Kit 0.0.23 device-id reply

Adds pico-explorer/ as a parallel CircuitPython firmware target alongside the 52Pi
Kit in pico-cp/. Same engine, same program-string grammar, same programs.json, same
live-sync protocol. Read-only on the device (no on-device beat editing); the web
editor's Live sync mirrors all edits in real time and the Explorer emits its own
play/stop/bpm/sel deltas back.

Hardware (Pimoroni Explorer PIM744):
- RP2350B + 2.8" ST7789V 320x240 LCD (8-bit parallel; CircuitPython's official
  board definition pre-builds the BusDisplay so we just use board.DISPLAY).
- 6 user buttons - A/B/C on the left of the screen, X/Y/Z on the right.
- Piezo speaker on GP12 (PWM) with amp enable on GP13.
- I2C QwSTEMMA on GP20/21 - reserved, unused by the firmware.
- No touchscreen, no joystick, no RGB LED. Run state shows on a tiny on-screen dot.

Buttons:
- A = play/stop. B = tap tempo. C = menu.
- X = prev track (hold-repeat). Z = next track (hold-repeat).
- Y = tempo -1 (hold-repeat; -5 after 1.5s).
- X+Z chord = tempo +1 (mirrors Y).
- In a menu: X/Z move the row cursor, Y decrements, A cycles/increments/selects,
  B = back, C = close.

Files added:
- pico-explorer/{boot.py, code.py, app.py, programs.json, README.md}.
  app.py = 1444 lines (~73KB source -> 29.8KB compiled .mpy).
- info-explorer.html.

Files touched:
- pico-cp/app.py: bump to 0.0.23. Version-query (SysEx 0x02 -> 0x03) reply now
  includes the device id as "K;<version>" (backward-compat: editor parses
  "contains ';'?" - old firmware sent bare version, treated as K).
- editor.html + editor-beta.html: _parseDeviceReply() splits id;version, FW_PATHS
  maps id to .py/.mpy URL pair, so Update firmware now pushes the right binary.
- build.sh + deploy.sh: precompile pico-explorer/app.py -> dist/explorer-app.mpy,
  zip pm_x1_circuitpy.zip alongside pm_k1_circuitpy.zip, ship
  pico-explorer-app.{py,mpy} next to pico-cp-app.{py,mpy}.
- docs/livesync-protocol.md: new section 7 - per-device emit/apply matrix.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

build.sh

@@ -19,6 +19,10 @@ MPYC="$PWD/tools/mpy-cross"; ROOT="$PWD"
 [[ -x "$MPYC" ]] || { echo "error: $MPYC missing (Adafruit mpy-cross for CircuitPython 10.2.1)" >&2; exit 1; }
 ( cd pico-cp && "$MPYC" app.py -o "$ROOT/dist/app.mpy" )   # compile from pico-cp/ so tracebacks read "app.py"
 echo "precompiled dist/app.mpy ($(stat -c%s dist/app.mpy) bytes <- $(stat -c%s pico-cp/app.py) source)"
+# PM_X-1 Explorer firmware uses the same mpy-cross. Output as dist/explorer-app.mpy so the Kit + Explorer
+# bundles each ship their own precompiled binary; the served URLs follow the same one-target-per-file rule.
+( cd pico-explorer && "$MPYC" app.py -o "$ROOT/dist/explorer-app.mpy" )
+echo "precompiled dist/explorer-app.mpy ($(stat -c%s dist/explorer-app.mpy) bytes <- $(stat -c%s pico-explorer/app.py) source)"
 
 python3 - <<'PY'
 import os, pathlib, re
@@ -40,7 +44,7 @@ def build(name):
 
 for name in ("index.html","editor.html","editor-beta.html","player.html","teacher.html","stage.html","micro.html","showcase.html","kit.html",
              "embed.html",
-             "info-editor.html","info-player.html","info-teacher.html","info-stage.html","info-micro.html","info-showcase.html","info-kit.html"):
+             "info-editor.html","info-player.html","info-teacher.html","info-stage.html","info-micro.html","info-showcase.html","info-kit.html","info-explorer.html"):
     print("built %s (%dKB)" % (name, build(name) // 1024))
 pathlib.Path("dist/embed.js").write_text(pathlib.Path("embed.js").read_text())   # loader, served as-is
 print("copied embed.js")
@@ -55,6 +59,12 @@ pathlib.Path("dist/pico-cp-app.py").write_text(_appsrc)   # served for version r
 # the editor pushes the PRECOMPILED .mpy (base64); serve it next to the source
 pathlib.Path("dist/pico-cp-app.mpy").write_bytes(pathlib.Path("dist/app.mpy").read_bytes())
 print("copied pico-cp-app.py + pico-cp-app.mpy")
+_xsrc = pathlib.Path("pico-explorer/app.py").read_text()                           # PM_X-1 Explorer firmware (sibling to the Kit)
+_xbad = [(i, c) for i, c in enumerate(_xsrc) if ord(c) > 0x7F]
+assert not _xbad, "pico-explorer/app.py has non-ASCII at %r -- keep it ASCII (version regex + clean source)" % (_xbad[:5],)
+pathlib.Path("dist/pico-explorer-app.py").write_text(_xsrc)                         # editor reads APP_VERSION from here
+pathlib.Path("dist/pico-explorer-app.mpy").write_bytes(pathlib.Path("dist/explorer-app.mpy").read_bytes())
+print("copied pico-explorer-app.py + pico-explorer-app.mpy")
 import zipfile  # PM_K-1 CircuitPython drive bundle (download → unzip onto CIRCUITPY)
 with zipfile.ZipFile("dist/pm_k1_circuitpy.zip", "w", zipfile.ZIP_DEFLATED) as z:
     for f in ("code.py", "boot.py", "programs.json", "font_s.bin", "font_m.bin", "font_l.bin",
@@ -63,4 +73,13 @@ with zipfile.ZipFile("dist/pm_k1_circuitpy.zip", "w", zipfile.ZIP_DEFLATED) as z
     z.write("dist/app.mpy", "app.mpy")                # the precompiled firmware (NOT app.py - too big to compile on-device)
     z.write("dist/editor.html", "editor.html")        # offline copy of the editor, on the drive
 print("zipped pm_k1_circuitpy.zip")
+# PM_X-1 Explorer drive bundle (download → unzip onto CIRCUITPY on the Pimoroni Explorer with CircuitPython for Pico 2)
+with zipfile.ZipFile("dist/pm_x1_circuitpy.zip", "w", zipfile.ZIP_DEFLATED) as z:
+    for f in ("code.py", "boot.py", "programs.json", "README.md"):
+        z.write("pico-explorer/" + f, f)
+    for f in ("font_s.bin", "font_m.bin", "font_l.bin", "logo.bin", "midi.bin", "usb.bin"):
+        z.write("pico-cp/" + f, f)                    # fonts + icons are resolution-agnostic; reuse the Kit's baked blobs
+    z.write("dist/explorer-app.mpy", "app.mpy")
+    z.write("dist/editor.html", "editor.html")
+print("zipped pm_x1_circuitpy.zip")
 PY

deploy.sh

@@ -42,7 +42,7 @@ fi
 echo "deployed v$BUILD -> $DEST_DIR"
 for f in index.html editor.html editor-beta.html player.html teacher.html stage.html micro.html showcase.html kit.html \
          embed.html \
-         info-editor.html info-player.html info-teacher.html info-stage.html info-micro.html info-showcase.html info-kit.html; do
+         info-editor.html info-player.html info-teacher.html info-stage.html info-micro.html info-showcase.html info-kit.html info-explorer.html; do
   sed "s|const APP_VERSION = \"[^\"]*\";|const APP_VERSION = \"$BUILD\";|" "$DIST_DIR/$f" > "$DEST_DIR/$f"
   echo "  $f ($(stat -c '%s' "$DEST_DIR/$f") bytes)"
 done
@@ -51,6 +51,9 @@ cp "$DIST_DIR/pico-main.py" "$DEST_DIR/pico-main.py"; echo "  pico-main.py ($(st
 cp "$DIST_DIR/pm_k1_circuitpy.zip" "$DEST_DIR/pm_k1_circuitpy.zip"; echo "  pm_k1_circuitpy.zip ($(stat -c '%s' "$DEST_DIR/pm_k1_circuitpy.zip") bytes)"  # PM_K-1 CircuitPython bundle
 cp "$DIST_DIR/pico-cp-app.py" "$DEST_DIR/pico-cp-app.py"; echo "  pico-cp-app.py ($(stat -c '%s' "$DEST_DIR/pico-cp-app.py") bytes)"  # served for version reading + reference
 cp "$DIST_DIR/pico-cp-app.mpy" "$DEST_DIR/pico-cp-app.mpy"; echo "  pico-cp-app.mpy ($(stat -c '%s' "$DEST_DIR/pico-cp-app.mpy") bytes)"  # precompiled firmware the editor pushes (base64)
+cp "$DIST_DIR/pm_x1_circuitpy.zip" "$DEST_DIR/pm_x1_circuitpy.zip"; echo "  pm_x1_circuitpy.zip ($(stat -c '%s' "$DEST_DIR/pm_x1_circuitpy.zip") bytes)"  # PM_X-1 Explorer CircuitPython bundle
+cp "$DIST_DIR/pico-explorer-app.py" "$DEST_DIR/pico-explorer-app.py"; echo "  pico-explorer-app.py ($(stat -c '%s' "$DEST_DIR/pico-explorer-app.py") bytes)"  # served for version reading
+cp "$DIST_DIR/pico-explorer-app.mpy" "$DEST_DIR/pico-explorer-app.mpy"; echo "  pico-explorer-app.mpy ($(stat -c '%s' "$DEST_DIR/pico-explorer-app.mpy") bytes)"  # PM_X-1 firmware (the editor pushes this when device id = X)
 rm -f "$DEST_DIR/player-asbuilt.html"        # renamed to teacher.html
 rm -f "$DEST_DIR/concepts.html"              # Concepts is now the landing (/)
 # info-*.html are first-class pages again: each form factor has a lean widget page

docs/livesync-protocol.md

@@ -193,3 +193,20 @@ target.
 - Streaming the device practice log (`history.json`) up to the browser.
 - Mirroring device `settings.json` (LED brightness, MIDI config, etc.).
 - Multi‑peer / multi‑editor arbitration beyond last‑writer‑wins.
+
+---
+
+## 7. Per‑device emit/apply matrix
+
+Both targets implement the **full apply path** for every verb. They differ in what
+they **emit**, because on‑device editing differs:
+
+| Device      | Emits                                              | Applies                                     |
+|-------------|----------------------------------------------------|---------------------------------------------|
+| **PM_K‑1** Kit (touchscreen + joystick) | `play` / `stop` / `bpm` / `sel` / `beat` / `lane` (FULL on structural lane edits) | all of the above |
+| **PM_X‑1** Explorer (6 buttons, read‑only beats) | `play` / `stop` / `bpm` / `sel` only (no on‑device beat/lane editing) | all of the above |
+
+Editors don't need to special‑case the source — both DELTA streams look identical on
+the wire, and the **device id is only exposed on the version query** (SysEx `0x02`
+→ `0x03` reply, `<id>;<version>`; pre‑0.0.23 firmware sends bare version → assume
+`K`).

editor-beta.html

@@ -1211,34 +1211,42 @@ async function toggleDeviceAudio() {
 function _queryDeviceVersion() {   // ask the device its firmware version (SysEx 0x02 -> reply 0x03)
   return new Promise((res) => { _verCb = res; _send([0xF0, 0x7D, 0x02, 0xF7]); setTimeout(() => { if (_verCb) { _verCb = null; res(null); } }, 1500); });
 }
+// 0.0.23+ devices reply "<id>;<version>" (e.g. "K;0.0.23", "X;0.0.1"); pre-0.0.23 send bare version -> assume K.
+function _parseDeviceReply(s) {
+  if (!s) return { id: null, version: null };
+  const i = s.indexOf(";");
+  return i >= 0 ? { id: s.slice(0, i), version: s.slice(i + 1) } : { id: "K", version: s };
+}
+const FW_PATHS = { K: { py: "/pico-cp-app.py",       mpy: "/pico-cp-app.mpy",       label: "PM_K-1 Kit" },
+                   X: { py: "/pico-explorer-app.py", mpy: "/pico-explorer-app.mpy", label: "PM_X-1 Explorer" } };
 async function updateFirmware() {   // A/B firmware update over USB-MIDI: push the precompiled .mpy
   console.log("[fw] update start");
   if (!(await _ensureMidi()) || !_midiOutputs().length) {
     console.log("[fw] no MIDI output (outputs:", _midiOutputs().length, ")");
-    return alert("Connect the PM_K-1 (Chrome/Edge/Firefox), then try again.");
+    return alert("Connect the device (Chrome/Edge/Firefox), then try again.");
   }
   console.log("[fw] MIDI ok; outputs:", _midiOutputs().map((o) => o.name));
-  const dev = await _queryDeviceVersion();
-  console.log("[fw] device version reply:", dev);
+  const reply = await _queryDeviceVersion();
+  const { id: devId, version: dev } = _parseDeviceReply(reply);
+  const paths = FW_PATHS[devId] || FW_PATHS.K;     // unknown id -> assume Kit (pre-0.0.23 firmware)
+  console.log("[fw] device reply:", reply, "-> id:", devId || "(none)", "version:", dev, "paths:", paths.label);
   let latest = null, b64 = null;
-  // version comes from the (text) source; the payload is the precompiled .mpy bytecode — CircuitPython
-  // compiles a big .py at boot, which OOMs the RP2040, so we ship + push compiled bytecode instead.
   for (const base of ["", "https://metronome.varasys.io"]) {
-    try { const t = await (await fetch(base + "/pico-cp-app.py", { cache: "no-store" })).text();
+    try { const t = await (await fetch(base + paths.py, { cache: "no-store" })).text();
           const m = t.match(/APP_VERSION\s*=\s*["']([^"']+)["']/); if (m) latest = m[1]; } catch (_) {}
-    try { const r = await fetch(base + "/pico-cp-app.mpy", { cache: "no-store" });
+    try { const r = await fetch(base + paths.mpy, { cache: "no-store" });
           if (r.ok) { b64 = _b64(new Uint8Array(await r.arrayBuffer())); break; } } catch (_) {}
   }
   if (!b64) {                                                // offline: let the user pick app.mpy
     alert("Can't reach the site.\n\nPick the firmware file (app.mpy) to flash — download it from\n" +
-          "metronome.varasys.io/pico-cp-app.mpy, or use the online editor at metronome.varasys.io/editor.html.");
+          "metronome.varasys.io" + paths.mpy + ", or use the online editor at metronome.varasys.io/editor.html.");
     const u8 = await _pickBinary(); if (!u8) return;
     b64 = _b64(u8); if (!latest) latest = "(picked .mpy)";
   }
   if (!latest) latest = "?";
   console.log("[fw] latest:", latest, "| .mpy base64 length:", b64 && b64.length);
   const upToDate = dev && dev === latest;
-  if (!confirm("Device firmware: " + (dev || "unknown") + "\nNew build: " + latest +
+  if (!confirm(paths.label + " firmware: " + (dev || "unknown") + "\nNew build: " + latest +
       (upToDate ? "\n\nSame version. Re-install anyway?"
                 : "\n\nUpdate now? The device reboots, runs the new build, and auto-rolls-back if it fails to start."))) {
     console.log("[fw] confirm returned false (cancelled, OR the browser is suppressing dialogs -> reload the page)");

editor.html

@@ -1204,34 +1204,42 @@ async function toggleDeviceAudio() {
 function _queryDeviceVersion() {   // ask the device its firmware version (SysEx 0x02 -> reply 0x03)
   return new Promise((res) => { _verCb = res; _send([0xF0, 0x7D, 0x02, 0xF7]); setTimeout(() => { if (_verCb) { _verCb = null; res(null); } }, 1500); });
 }
+// 0.0.23+ devices reply "<id>;<version>" (e.g. "K;0.0.23", "X;0.0.1"); pre-0.0.23 send bare version -> assume K.
+function _parseDeviceReply(s) {
+  if (!s) return { id: null, version: null };
+  const i = s.indexOf(";");
+  return i >= 0 ? { id: s.slice(0, i), version: s.slice(i + 1) } : { id: "K", version: s };
+}
+const FW_PATHS = { K: { py: "/pico-cp-app.py",       mpy: "/pico-cp-app.mpy",       label: "PM_K-1 Kit" },
+                   X: { py: "/pico-explorer-app.py", mpy: "/pico-explorer-app.mpy", label: "PM_X-1 Explorer" } };
 async function updateFirmware() {   // A/B firmware update over USB-MIDI: push the precompiled .mpy
   console.log("[fw] update start");
   if (!(await _ensureMidi()) || !_midiOutputs().length) {
     console.log("[fw] no MIDI output (outputs:", _midiOutputs().length, ")");
-    return alert("Connect the PM_K-1 (Chrome/Edge/Firefox), then try again.");
+    return alert("Connect the device (Chrome/Edge/Firefox), then try again.");
   }
   console.log("[fw] MIDI ok; outputs:", _midiOutputs().map((o) => o.name));
-  const dev = await _queryDeviceVersion();
-  console.log("[fw] device version reply:", dev);
+  const reply = await _queryDeviceVersion();
+  const { id: devId, version: dev } = _parseDeviceReply(reply);
+  const paths = FW_PATHS[devId] || FW_PATHS.K;     // unknown id -> assume Kit (pre-0.0.23 firmware)
+  console.log("[fw] device reply:", reply, "-> id:", devId || "(none)", "version:", dev, "paths:", paths.label);
   let latest = null, b64 = null;
-  // version comes from the (text) source; the payload is the precompiled .mpy bytecode — CircuitPython
-  // compiles a big .py at boot, which OOMs the RP2040, so we ship + push compiled bytecode instead.
   for (const base of ["", "https://metronome.varasys.io"]) {
-    try { const t = await (await fetch(base + "/pico-cp-app.py", { cache: "no-store" })).text();
+    try { const t = await (await fetch(base + paths.py, { cache: "no-store" })).text();
           const m = t.match(/APP_VERSION\s*=\s*["']([^"']+)["']/); if (m) latest = m[1]; } catch (_) {}
-    try { const r = await fetch(base + "/pico-cp-app.mpy", { cache: "no-store" });
+    try { const r = await fetch(base + paths.mpy, { cache: "no-store" });
           if (r.ok) { b64 = _b64(new Uint8Array(await r.arrayBuffer())); break; } } catch (_) {}
   }
   if (!b64) {                                                // offline: let the user pick app.mpy
     alert("Can't reach the site.\n\nPick the firmware file (app.mpy) to flash — download it from\n" +
-          "metronome.varasys.io/pico-cp-app.mpy, or use the online editor at metronome.varasys.io/editor.html.");
+          "metronome.varasys.io" + paths.mpy + ", or use the online editor at metronome.varasys.io/editor.html.");
     const u8 = await _pickBinary(); if (!u8) return;
     b64 = _b64(u8); if (!latest) latest = "(picked .mpy)";
   }
   if (!latest) latest = "?";
   console.log("[fw] latest:", latest, "| .mpy base64 length:", b64 && b64.length);
   const upToDate = dev && dev === latest;
-  if (!confirm("Device firmware: " + (dev || "unknown") + "\nNew build: " + latest +
+  if (!confirm(paths.label + " firmware: " + (dev || "unknown") + "\nNew build: " + latest +
       (upToDate ? "\n\nSame version. Re-install anyway?"
                 : "\n\nUpdate now? The device reboots, runs the new build, and auto-rolls-back if it fails to start."))) {
     console.log("[fw] confirm returned false (cancelled, OR the browser is suppressing dialogs -> reload the page)");

hardware/BOM.csv

@@ -0,0 +1,36 @@
+Ref,Block,Part,Manufacturer,MPN,Qty,Approx_USD_ea,Notes
+U1,MCU,RP2350A microcontroller,Raspberry Pi,RP2350A,1,1.10,QFN-60; mind E9 input-latch erratum (external pulldowns)
+U2,MCU,16MB QSPI flash,Winbond,W25Q128JVSIQ,1,1.20,genuine part; firmware wear-levels history.json
+Y1,MCU,12MHz crystal,Abracon,ABM8-272-12.000MHZ,1,0.30,+/-30ppm
+U3,Power,3V3 IO LDO,Diodes Inc,AP2112K-3.3TRG1,1,0.25,digital domain
+L1,Power,RP2350 core SMPS inductor,TDK,VLS3012,1,0.15,per RP2350 reference
+U4,Power,Dual boost/inverter +/-18V,Texas Instruments,TPS65131RGER,1,2.50,raw +/-18V from 5V; guarded corner
+U5,Power,Ultra-low-noise +15V LDO,Texas Instruments,TPS7A4901DGNR,1,1.80,post-regulates +18 to clean +15
+U6,Power,Ultra-low-noise -15V LDO,Texas Instruments,TPS7A3001DGNR,1,1.90,post-regulates -18 to clean -15
+J1,Power/USB,USB-C receptacle (TH-anchored),GCT,USB4085-GF-A,1,0.60,through-hole anchor tabs for strain
+U7,Power/USB,USB ESD protection array,STMicroelectronics,USBLC6-2SC6,1,0.30,D+/D-/CC/VBUS
+FL1,Power/USB,USB common-mode choke,Wurth,744232090,1,0.35,data-pair EMI
+U8,Click,I2S audio DAC,Texas Instruments,PCM5102APWR,1,2.20,Burr-Brown; reliability-first
+X1,Click,Low-jitter audio oscillator,Abracon,ASEM1-24.576MHZ-LR-T,1,1.40,dedicated MCLK; not PIO-jittered
+U9,Audio-in,Balanced line receiver,THAT Corp,THAT1240S08-U,1,3.20,0dB unity; pinout verified doc600035 rev05; 2nd-src INA134/SSM2141
+U10,Audio-in,JFET Hi-Z instrument buffer,Texas Instruments,OPA1641AID,1,1.60,>=1Mohm DI buffer + gain
+U11,Audio-mix,Dual audio op-amp (sum/filter),Texas Instruments,OPA1612AIDR,1,2.40,signal-path low noise
+U12,Audio-out,Balanced line driver,THAT Corp,THAT1646S08-U,1,3.30,near-zero source; 47ohm build-out per leg; pinout TBV at output stage
+RV1,Audio-out,Output level cal trimmer 25-turn,Bourns,3296W-1-103LF,1,0.70,factory-set DAC FS -> +4dBu
+U13,Indicator,Dual comparator (sig/clip),Texas Instruments,LM393DR,1,0.15,peak-detect -> RP2350 GPIO + LED lines
+K1,Audio-in,Signal relay line/inst (DPDT gold),Panasonic,TQ2SA-5V,1,1.30,sealed gold bifurcated contacts
+K2,Audio-out,Mute relay (fail-safe DPDT gold),Panasonic,TQ2SA-5V,1,1.30,de-energized=muted
+K3,Audio-out,Ground-lift relay (gold),Panasonic,TQ2SA-5V,1,1.30,series with face panel switch; soft-lift 100R||10nF
+U14,Control,Relay driver array,Texas Instruments,ULN2003ADR,1,0.20,drives K1-K3 with flyback
+U15,RTC,Real-time clock (integrated xtal),Micro Crystal,RV-8803-C7,1,1.50,I2C on touch bus; drift irrelevant
+BT1,RTC,CR2032 holder (socketed),Keystone,1066,1,0.30,user-replaceable
+U16,MIDI(DNP),Opto-isolator MIDI IN,Vishay,H11L1M,1,0.55,DNP populate-option
+U17,MIDI(DNP),Hex Schmitt buffer MIDI OUT/THRU,Nexperia,74LVC14APW,1,0.20,DNP populate-option
+U18,Speaker(DNP),Class-D mono amp,Diodes Inc,PAM8302AASCR,1,0.35,DNP monitor option per face
+J2,Interconnect,Digital ribbon header 2x13 shrouded keyed,Wurth,61303421821,1,0.45,Pico-pinout-compatible
+J3,Interconnect,Analog audio header 2x5 shrouded keyed,Wurth,61301021821,1,0.35,twisted/shielded; away from digital
+J4,Interconnect,MIDI header 1x6,Wurth,61300611121,1,0.20,used only if DNP MIDI populated
+J5,Debug,SWD Cortex-Debug 2x5 1.27mm,Samtec,FTSH-105-01-L-DV-K,1,0.50,service header
+D-arr,ESD,Interconnect ESD clamp arrays,Texas Instruments,TPD2E2U06DCKR,3,0.10,on user-touchable lines
+PASS,Passives,Film caps / 0.1% thin-film R / clamp diodes / ferrites,various,various,1,4.00,WIMA film signal caps; Panasonic ERA 0.1%; no electrolytics in signal path
+PCB,Fabrication,4-layer PCB ENIG finish,JLCPCB/PCBWay,custom,1,3.00,gold finish; qty-dependent

hardware/DESIGN.md

@@ -0,0 +1,211 @@
+# PM_K-1 Core Board ("brain") — design-of-record
+
+VARASYS PolyMeter · heirloom pro-audio · modular brain/face architecture
+Status: **design-of-record / pre-layout.** Component selection complete; PCB routing is the
+remaining interactive step (see [Open items](#open-items)).
+
+---
+
+## 1. Philosophy
+
+This is meant to be a device people hand down to their great-grandkids. The core board carries
+**all the active electronics** and is specced to pro/audiophile tier with longevity and
+serviceability as first-class goals. We do **not** value-engineer the audio path.
+
+The user selects the face/enclosure/connector components; this document specs only the **core**.
+
+## 2. Architecture — modular brain/face
+
+- **Core ("brain"):** RP2350 + power + RTC + the full pro-audio analog chain + control logic.
+  One core design is reused across every form factor.
+- **Face ("form factor"):** display, touch, joystick, buttons, LED, speaker, the physical
+  audio/MIDI connectors, panel switches, enclosure. **The core never decides connector type.**
+- **Two interconnects, deliberately separate** (§7):
+  1. a **digital ribbon** whose pinout mirrors the Raspberry Pi Pico, so a stock Pico/Pico 2 on a
+     test adapter can drive any face board for bring-up;
+  2. an **analog interconnect** (+ a small MIDI interconnect) kept physically away from the fast
+     digital ribbon, because a balanced audio signal must never run parallel to the 24 MHz display SPI.
+
+## 3. Block diagram
+
+```
+USB-C 5V ─┬─► 3V3 LDO ──────────────────────► RP2350 (core reg + ext L) + W25Q128 16MB + RV-8803 RTC(+CR2032)
+          │                                            │ I²S + low-jitter MCLK
+          └─► TPS65131 ±18V ─► TPS7A49/30 LDO ─► clean ±15V          ▼
+                                                          PCM5102A DAC ──► [summing: click + input]
+                                                                                    │
+  bal IN ─[ESD/DC-block/clamp/series-R]─► [LINE/INST relay] ─┬─ THAT1240 receiver ──┘
+  (analog interconnect)                                      └─ OPA1641 Hi-Z DI buffer (+gain)
+                                                                                    │
+                                              THAT1646 balanced driver ─[47Ω build-out]─► [MUTE relay]─► bal OUT
+                                                                                    shield ─[panel SW]─[GND-LIFT relay]─ gnd
+  sig/clip peak detect ─► LM393 ─► RP2350 GPIO (UI) + LED lines (interconnect)
+  RP2350 UART ─► [DNP: H11L1 opto IN + 74LVC14 buffer OUT] ─► MIDI interconnect   (USB-MIDI = default)
+```
+
+## 4. Functional blocks
+
+### 4.1 MCU + digital
+- **RP2350A** (QFN-60, 30 GPIO). Chosen over RP2040 as the newest in-house part: dual M33+RISC-V,
+  520 KB RAM, secure boot, longest production runway. Firmware runs unchanged.
+  - **Erratum E9:** high-impedance inputs can latch — every input we read (face switches, buttons)
+    gets an **external pulldown**, never relies on the internal pad alone.
+  - Core supply via the RP2350 on-chip switched-mode regulator (external inductor); 3V3 IO from an
+    external LDO (AP2112K-3.3 / TLV75533).
+- **Flash:** Winbond **W25Q128JV** (16 MB) — genuine part; the CircuitPython appliance bundles the
+  editor + tracks on a USB drive. Firmware does wear-leveling for `history.json`.
+- **Crystal:** 12 MHz ±30 ppm.
+- **Debug/service:** SWD 2×5 Cortex-Debug header + labeled test points (rails, I²S, audio nodes).
+
+### 4.2 Click source (DAC)
+- **TI/Burr-Brown PCM5102A** I²S DAC — reliability-first, widely stocked for future repair.
+- Fed by a **dedicated low-jitter audio oscillator** (22.5792/24.576 MHz MEMS XO), **not** an MCLK
+  jittered out of the RP2350 PIO — jitter is audible as a raised noise floor.
+
+### 4.3 Analog audio chain (the heart)
+- **Input (balanced, switchable line/instrument):**
+  - **Line mode:** THAT1240 laser-trimmed balanced receiver (~high CMRR, no hand-matched resistors).
+  - **Instrument mode:** OPA1641 JFET Hi-Z buffer (≥1 MΩ) + ~+10–15 dB gain (active DI).
+  - Selected by a **gold-contact signal relay** on the core (1 GPIO; touchscreen toggle, optional
+    face panel switch on a separate GPIO input).
+  - **Protection (non-negotiable):** series DC-blocking film cap (blocks +48 V phantom — the real
+    input-killer), clamp diodes/TVS to the rails, series current-limit resistor. A wrong-mode plug
+    then only *sounds* wrong; nothing is damaged.
+- **Mix:** digital/firmware (touchscreen). Analog stage at unity; click level set via the DAC.
+- **Output driver:** THAT1646 balanced line driver, **47 Ω build-out per leg** for
+  cable-capacitance stability and short-circuit tolerance (§5.1).
+- **No electrolytics in the signal path** — film coupling caps (WIMA). 0.1 % thin-film resistors.
+
+### 4.4 Output protection / conditioning
+- **Power-up/down mute relay** — fail-safe, **de-energized = muted** (shorts hot+cold to gnd). A
+  hardware rail supervisor + RC turn-on delay un-mutes only after ±15 V settles; on power loss the
+  coil drops and mutes *faster than the rails can thump*. **Not MCU-dependent.** The MCU can *also*
+  assert mute (for clean line/inst flips and DAC reconfig).
+- **Ground-lift** — both a **face panel switch** and a **core GPIO relay**, wired in **series** in
+  the shield-ground path: bonded only when both closed, either opening lifts it. **Soft lift =
+  100 Ω ∥ 10 nF** (not a hard open) so RF/safety keeps a path.
+
+### 4.5 RTC
+- **Micro Crystal RV-8803** (integrated 32.768 kHz crystal → no second crystal near the RP2350's
+  own) + **CR2032 in a socketed holder**. Shares the touch I²C bus (no extra GPIO). Drift is
+  irrelevant for a practice-log timestamp; reliability and zero-fuss layout win.
+
+### 4.6 MIDI (default USB, hardware optional)
+- **USB-MIDI is the default** and already in firmware — IN/OUT/THRU are software routing to a
+  computer/tablet host. Zero extra parts.
+- **Dedicated DIN/TRS MIDI is a DNP populate-option:** the RP2350 UART lines route to the MIDI
+  interconnect with **H11L1 opto IN + 74LVC14 buffered OUT/THRU footprints left unpopulated**.
+  A "stage" face can populate them for laptop-free hardware sync. (USB-MIDI can't peer-to-peer with
+  standalone DIN gear — the device is a USB *peripheral*, not a host — which is why the hardware
+  option stays available.) Analog pulse/clock sync: **not included** (MIDI only).
+
+### 4.7 Monitor speaker
+- **DNP-optional** class-D amp (PAM8302) footprint on the core; speaker +/- routed on the analog
+  interconnect. Populated only for form factors that want a built-in monitor.
+
+## 5. The five remaining pro details (decided)
+
+### 5.1 Output impedance & level calibration
+- THAT1646 source impedance is near-zero; **47 Ω build-out resistors** per leg give stable driving
+  into long/capacitive cables and survive a shorted output.
+- **Level calibration:** a 25-turn precision trimmer (Bourns 3296W) in the driver gain network,
+  factory-set so DAC full-scale → **+4 dBu nominal**, leaving ~**+24 dBu** peak headroom on ±15 V.
+  Set-and-forget on the core; not a face control.
+
+### 5.2 Signal / clip indication
+- A peak detector (Schottky + hold cap) on the input (signal-present, ~−40 dBu) and on the
+  driver-input/summing node (clip, within ~3 dB of rail) feeds an **LM393** dual comparator.
+- Comparator outputs go to **RP2350 GPIOs** (clip/signal shown on the touchscreen) **and** are
+  mirrored to **SIG/CLIP LED drive lines on the digital interconnect** so a face can fit discrete LEDs.
+
+### 5.3 ESD / EMI hardening
+- **USB-C:** USBLC6-2SC6 (or TPD4E05U06) ESD array on D±/CC/VBUS; common-mode choke on the data
+  pair; shell bonded to chassis via RC; ferrite + TVS + bulk on VBUS.
+- **Interconnects:** ~33 Ω series on fast SPI lines for edge-rate control; ESD clamp arrays on any
+  line reaching a user-touchable cable; interleaved ground pins; ferrite beads where 3V3/5V cross
+  into the analog domain.
+- **Board:** full ground planes + stitching vias; the boost/inverter switcher lives in a guarded
+  corner away from the analog section; analog/digital grounds meet at a single **star point**.
+- **Heirloom option:** conformal coating for humidity/longevity (build-time choice).
+
+### 5.4 Chassis / strain-relief (core-side)
+- 4× **M3 mounting holes** with keep-outs; a dedicated chassis-ground pad/pin.
+- **Through-hole-anchored USB-C** jack (SMD-only tabs shear off with cable wiggle — unacceptable for
+  a 50-year device).
+- **Shrouded, keyed, latching** interconnect headers (can't insert backward or vibrate loose).
+- Panel strain-relief and connector mounting live on the face/enclosure.
+
+### 5.5 Interconnect pinout — see §7.
+
+## 6. Power tree
+
+| Rail | Source | Part | Notes |
+|---|---|---|---|
+| +5 V | USB-C VBUS | — | ferrite + TVS + bulk |
+| +3V3 (IO) | LDO from 5 V | AP2112K-3.3 / TLV75533 | digital domain |
+| +1.1 V core | RP2350 internal SMPS | (external inductor) | per RP2350 ref |
+| ±18 V (raw) | dual boost/inverter from 5 V | **TPS65131** | switcher, guarded corner |
+| **±15 V (clean)** | ultra-low-noise LDO | **TPS7A4901 (+) / TPS7A3001 (−)** | feeds all audio op-amps |
+
+## 7. Interconnect pinouts
+
+### 7.1 Digital ribbon — 2×13 (26-pin) IDC, Pico-pinout-compatible
+Grounds interleaved around SPI. A Pico/Pico 2 test adapter maps these to the listed GP.
+
+| Pin | Signal | GP | | Pin | Signal | GP |
+|----|--------|----|--|----|--------|----|
+| 1 | +5V | — | | 2 | GND | — |
+| 3 | +3V3 | — | | 4 | GND | — |
+| 5 | SPI_SCK | GP2 | | 6 | GND | — |
+| 7 | SPI_MOSI | GP3 | | 8 | LCD_CS | GP5 |
+| 9 | LCD_DC | GP6 | | 10 | LCD_RST | GP7 |
+| 11 | GND | — | | 12 | I2C_SDA | GP8 |
+| 13 | I2C_SCL | GP9 | | 14 | GND | — |
+| 15 | JOY_X (ADC0) | GP26 | | 16 | JOY_Y (ADC1) | GP27 |
+| 17 | BTN_A | GP15 | | 18 | BTN_B | GP14 |
+| 19 | WS2812 | GP12 | | 20 | GND | — |
+| 21 | GNDLIFT_SW (in) | GP21 | | 22 | LINEINST_SW (in) | GP22 |
+| 23 | SIG_LED | GP19 | | 24 | CLIP_LED | GP20 |
+| 25 | GND | — | | 26 | GND | — |
+
+*I²S (BCK/LRCK/DOUT), the relays (line/inst route GP16, mute GP18, gnd-lift GP17), and MCLK stay
+on-core — they are not on the ribbon. A Pico test brain drives the digital/face I/O above but
+**cannot** drive the analog chain (DAC/op-amps are core-only).*
+
+### 7.2 Analog audio interconnect — 2×5 (10-pin), twisted/shielded, away from digital
+| Pin | Signal | | Pin | Signal |
+|----|--------|--|----|--------|
+| 1 | AOUT_HOT | | 2 | AGND |
+| 3 | AOUT_COLD | | 4 | CHASSIS/SHIELD (face side of ground-lift) |
+| 5 | AIN_HOT | | 6 | AGND |
+| 7 | AIN_COLD | | 8 | SPK+ (DNP) |
+| 9 | AGND | | 10 | SPK− (DNP) |
+
+### 7.3 MIDI interconnect — 1×6, only if DNP MIDI populated
+| Pin | Signal |
+|----|--------|
+| 1 | MIDI_OUT_A (TRS-A tip/ring leg) |
+| 2 | MIDI_OUT_B |
+| 3 | MIDI_IN_A (to opto) |
+| 4 | MIDI_IN_B |
+| 5 | +5V (OUT drive) |
+| 6 | GND / shield |
+
+## 8. BOM
+Full part list with manufacturer numbers and rough costs in **`hardware/BOM.csv`**. Headline parts:
+RP2350A · W25Q128JV · PCM5102A · THAT1240 + THAT1646 · OPA1641 · OPA1612 · TPS65131 + TPS7A4901/3001 ·
+RV-8803 · USBLC6-2SC6 · 3× Panasonic TQ2SA gold-contact relays · H11L1 (DNP).
+
+## 9. Manufacturing
+- **PCB:** ENIG (gold) finish — non-negotiable for decades of reliable contacts/solderability.
+- **Assembly:** JLCPCB/PCBWay PCBA, ~5-board prototype minimum; ~$80–200 first run. Core parts cost
+  ~$25–40/board one-off (pro op-amps + relays dominate), trending toward ~$15–20 at qty 100.
+- Most expensive items are the THAT audio ICs and the relays — that's where "heirloom" lives.
+
+## 10. Open items
+- **PCB layout/routing is the interactive next step** — placement, controlled-impedance USB pair,
+  star ground, switcher isolation, copper pours, DRC. The KiCad project under `hardware/kicad/`
+  is a documented schematic canvas + design-of-record; symbol placement and wiring happen in
+  Eeschema. `kicad-cli` is used here for ERC and PDF export verification.
+- Confirm the exact 3.5" ST7796/GT911 panel connector (FPC vs header) before finalizing the face.
+- Decide MIDI connector (TRS-MIDI Type-A vs DIN-5) per form factor — face decision.

hardware/eda/Containerfile

@@ -0,0 +1,36 @@
+# Reproducible EDA toolchain for the PM_K-1 core board.
+#
+# Why this exists: the system KiCad is 7.0 (no CLI ERC). This pins a known,
+# rebuildable environment so the design can be checked/simulated identically
+# years from now — fitting for a device meant to outlive its tools.
+#
+#   KiCad 9  -> schematic capture, CLI ERC/DRC, netlist/PDF/Gerber export
+#   ngspice  -> SPICE simulation of the analog audio circuits
+#   python3  -> scripting / BOM / skidl-style helpers
+#
+# Build/run via ../eda/run.sh (or: podman build -t pmk1-eda:9.0 .)
+FROM docker.io/library/ubuntu:24.04
+
+ENV DEBIAN_FRONTEND=noninteractive
+SHELL ["/bin/bash", "-o", "pipefail", "-c"]
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+        software-properties-common ca-certificates gnupg && \
+    add-apt-repository -y ppa:kicad/kicad-9.0-releases && \
+    apt-get update && apt-get install -y --no-install-recommends \
+        kicad \
+        kicad-symbols \
+        kicad-footprints \
+        ngspice \
+        python3 python3-pip python3-venv \
+        git make && \
+    apt-get clean && rm -rf /var/lib/apt/lists/* && \
+    pip3 install --no-cache-dir --break-system-packages skidl
+
+# Point SKiDL / KiCad CLI at the installed libraries (reproducible, not ad-hoc).
+ENV KICAD9_SYMBOL_DIR=/usr/share/kicad/symbols \
+    KICAD9_FOOTPRINT_DIR=/usr/share/kicad/footprints \
+    KICAD_SYMBOL_DIR=/usr/share/kicad/symbols
+
+WORKDIR /work
+CMD ["bash"]

hardware/eda/README.md

@@ -0,0 +1,36 @@
+# PM_K-1 EDA environment
+
+A reproducible container with the tools to design, check, and simulate the core board —
+so the work doesn't depend on whatever happens to be installed on a given machine, now or
+in 50 years.
+
+## What's inside
+- **KiCad 9** — schematic capture + PCB layout, and a CLI (`kicad-cli`) that can run
+  **ERC** (Electrical Rules Check) and DRC, and export netlists/PDF/Gerbers.
+- **ngspice** — SPICE simulator for validating the analog audio circuits before we commit
+  copper (op-amp stages, filters, input loading, etc.).
+- **python3** — scripting, BOM munging, optional code-defined-schematic helpers.
+
+## Why a container?
+The system KiCad here is 7.0, whose CLI can't run ERC (that arrived in KiCad 8). Rather than
+fight the host, we pin a known toolchain. Anyone — including future-you — rebuilds the exact
+environment with one command.
+
+## Use it
+```bash
+cd hardware/eda
+./run.sh                                   # interactive shell, lands in hardware/kicad/
+./run.sh kicad-cli version                 # confirm KiCad 9
+./run.sh kicad-cli sch erc pm_k1_core.kicad_sch   # run ERC on the schematic
+./run.sh ngspice -b ../eda/sim/input_loading.cir  # run a simulation (cwd is kicad/)
+```
+`run.sh` builds the image on first use, then mounts the whole repo at `/work` (so KiCad sees
+`hardware/`). Use `RUNTIME=docker ./run.sh …` to use Docker instead of Podman.
+
+## Layout
+```
+eda/
+  Containerfile      # the pinned toolchain (KiCad 9 + ngspice + python)
+  run.sh             # build-if-needed + run with the repo mounted
+  sim/               # ngspice decks (SPICE simulations of the analog circuits)
+```

hardware/eda/circuits/audio_chain.py

@@ -0,0 +1,195 @@
+#!/usr/bin/env python3
+"""PM_K-1 audio chain - INTEGRATED board netlist (SKiDL).
+
+Wires stages 1, 1b, 2, 3, 4 into one netlist with shared nets and DEDUPLICATED parts:
+  * the Stage-2 reconstruction filter and the Stage-3 summer share ONE OPA1612 dual
+    (U4: section A = filter, section B = summer) -- no parked half.
+  * the three relays (K1 select, K2 mute, K3 ground-lift) share ONE ULN2003 (U6).
+This is the source of truth for the integrated audio netlist; the per-stage circuits/
+files remain as the documented, individually-simulated building blocks.
+
+Run INSIDE the EDA container:
+    cd hardware/eda && ./run.sh python3 ../eda/circuits/audio_chain.py
+Outputs ERC + hardware/kicad/audio_chain.net.
+
+All IC pinouts datasheet-verified (see the per-stage files for the citations):
+  THAT1240 1=Ref 2=In- 3=In+ 4=Vee 5=Sns 6=Vout 7=Vcc 8=NC
+  OPA1641  1=NC 2=-IN 3=+IN 4=V- 5=NC 6=OUT 7=V+ 8=NC
+  OPA1612  1=OUTA 2=-INA 3=+INA 4=V- 5=+INB 6=-INB 7=OUTB 8=V+
+  PCM5102A (TSSOP-20) per TI SLAS859C
+  THAT1646 1=Out- 2=Sns- 3=Gnd 4=In 5=Vee 6=Vcc 7=Sns+ 8=Out+
+  TQ2SA    coil 1/10; pole1 COM3/NC4/NO2; pole2 COM8/NC7/NO9
+  ULN2003A in 1B-7B=1..7, out 1C-7C=16..10, GND=8, COM=9
+"""
+import os
+from skidl import *
+
+set_default_tool(KICAD9)
+
+R = Part("Device", "R", dest=TEMPLATE, footprint="Resistor_SMD:R_0805_2012Metric")
+C = Part("Device", "C", dest=TEMPLATE, footprint="Capacitor_SMD:C_0805_2012Metric")
+D = Part("Device", "D", dest=TEMPLATE, footprint="Diode_SMD:D_SOD-323")
+
+# ---------------- nets ----------------
+p15, n15, p3v3, p5, gnd = Net("+15V"), Net("-15V"), Net("+3V3"), Net("+5V"), Net("GND")
+for n in (p15, n15, p3v3, p5, gnd):
+    n.drive = POWER
+# audio signal flow
+ain_hot, ain_cold = Net("AIN_HOT"), Net("AIN_COLD")          # input jack tip/ring
+rx_hot_in = Net("RX_HOT_IN")                                  # relay-routed hot -> receiver
+rx_out, di_in, di_out = Net("RX_OUT"), Net("DI_IN"), Net("DI_OUT")
+stage1_out, click_out, mix_out = Net("STAGE1_OUT"), Net("CLICK_OUT"), Net("MIX_OUT")
+aout_hot, aout_cold, chassis = Net("AOUT_HOT"), Net("AOUT_COLD"), Net("CHASSIS")
+# DAC clocks/data + control
+mclk, i2s_bck, i2s_din, i2s_lrck = Net("MCLK"), Net("I2S_BCK"), Net("I2S_DIN"), Net("I2S_LRCK")
+dac_xsmt = Net("DAC_XSMT")
+sel_linst, mute_en, gndlift_en = Net("SEL_LINST"), Net("MUTE_EN"), Net("GNDLIFT_EN")
+k1_drv, k2_drv, k3_drv = Net("K1_DRV"), Net("K2_DRV"), Net("K3_DRV")
+
+# ---------------- part definitions ----------------
+def mk(name, pins, ref_prefix="U", fp="Package_SO:SOIC-8_3.9x4.9mm_P1.27mm"):
+    return Part(name=name, tool=SKIDL, dest=TEMPLATE, ref_prefix=ref_prefix, footprint=fp, pins=pins)
+
+P = Pin.types
+THAT1240 = mk("THAT1240", [Pin(num=1,name="REF",func=P.INPUT),Pin(num=2,name="IN-",func=P.INPUT),
+    Pin(num=3,name="IN+",func=P.INPUT),Pin(num=4,name="V-",func=P.PWRIN),Pin(num=5,name="SENSE",func=P.PASSIVE),
+    Pin(num=6,name="OUT",func=P.OUTPUT),Pin(num=7,name="V+",func=P.PWRIN),Pin(num=8,name="NC",func=P.NOCONNECT)])
+OPA1641 = mk("OPA1641", [Pin(num=1,name="NC1",func=P.NOCONNECT),Pin(num=2,name="-IN",func=P.INPUT),
+    Pin(num=3,name="+IN",func=P.INPUT),Pin(num=4,name="V-",func=P.PWRIN),Pin(num=5,name="NC5",func=P.NOCONNECT),
+    Pin(num=6,name="OUT",func=P.OUTPUT),Pin(num=7,name="V+",func=P.PWRIN),Pin(num=8,name="NC8",func=P.NOCONNECT)])
+OPA1612 = mk("OPA1612", [Pin(num=1,name="OUTA",func=P.OUTPUT),Pin(num=2,name="-INA",func=P.INPUT),
+    Pin(num=3,name="+INA",func=P.INPUT),Pin(num=4,name="V-",func=P.PWRIN),Pin(num=5,name="+INB",func=P.INPUT),
+    Pin(num=6,name="-INB",func=P.INPUT),Pin(num=7,name="OUTB",func=P.OUTPUT),Pin(num=8,name="V+",func=P.PWRIN)])
+THAT1646 = mk("THAT1646", [Pin(num=1,name="OUT-",func=P.OUTPUT),Pin(num=2,name="SNS-",func=P.INPUT),
+    Pin(num=3,name="GND",func=P.PWRIN),Pin(num=4,name="IN",func=P.INPUT),Pin(num=5,name="V-",func=P.PWRIN),
+    Pin(num=6,name="V+",func=P.PWRIN),Pin(num=7,name="SNS+",func=P.INPUT),Pin(num=8,name="OUT+",func=P.OUTPUT)])
+PCM5102A = mk("PCM5102A", [Pin(num=1,name="CPVDD",func=P.PWRIN),Pin(num=2,name="CAPP",func=P.PASSIVE),
+    Pin(num=3,name="CPGND",func=P.PWRIN),Pin(num=4,name="CAPM",func=P.PASSIVE),Pin(num=5,name="VNEG",func=P.PASSIVE),
+    Pin(num=6,name="OUTL",func=P.OUTPUT),Pin(num=7,name="OUTR",func=P.OUTPUT),Pin(num=8,name="AVDD",func=P.PWRIN),
+    Pin(num=9,name="AGND",func=P.PWRIN),Pin(num=10,name="DEMP",func=P.INPUT),Pin(num=11,name="FLT",func=P.INPUT),
+    Pin(num=12,name="SCK",func=P.INPUT),Pin(num=13,name="BCK",func=P.INPUT),Pin(num=14,name="DIN",func=P.INPUT),
+    Pin(num=15,name="LRCK",func=P.INPUT),Pin(num=16,name="FMT",func=P.INPUT),Pin(num=17,name="XSMT",func=P.INPUT),
+    Pin(num=18,name="LDOO",func=P.PWROUT),Pin(num=19,name="DGND",func=P.PWRIN),Pin(num=20,name="DVDD",func=P.PWRIN)],
+    fp="Package_SO:TSSOP-20_4.4x6.5mm_P0.65mm")
+TQ2SA = mk("TQ2SA-5V", [Pin(num=1,name="COIL_A",func=P.PASSIVE),Pin(num=10,name="COIL_B",func=P.PASSIVE),
+    Pin(num=3,name="P1_COM",func=P.PASSIVE),Pin(num=4,name="P1_NC",func=P.PASSIVE),Pin(num=2,name="P1_NO",func=P.PASSIVE),
+    Pin(num=8,name="P2_COM",func=P.PASSIVE),Pin(num=7,name="P2_NC",func=P.PASSIVE),Pin(num=9,name="P2_NO",func=P.PASSIVE),
+    Pin(num=5,name="NC5",func=P.NOCONNECT),Pin(num=6,name="NC6",func=P.NOCONNECT)],
+    ref_prefix="K", fp="Relay_SMD:Relay_DPDT_Panasonic_TQ2-SA")
+ULN2003 = mk("ULN2003A", [Pin(num=1,name="1B",func=P.INPUT),Pin(num=2,name="2B",func=P.INPUT),
+    Pin(num=3,name="3B",func=P.INPUT),Pin(num=4,name="4B",func=P.INPUT),Pin(num=5,name="5B",func=P.INPUT),
+    Pin(num=6,name="6B",func=P.INPUT),Pin(num=7,name="7B",func=P.INPUT),Pin(num=8,name="GND",func=P.PWRIN),
+    Pin(num=9,name="COM",func=P.PWRIN),Pin(num=10,name="7C",func=P.OPENCOLL),Pin(num=11,name="6C",func=P.OPENCOLL),
+    Pin(num=12,name="5C",func=P.OPENCOLL),Pin(num=13,name="4C",func=P.OPENCOLL),Pin(num=14,name="3C",func=P.OPENCOLL),
+    Pin(num=15,name="2C",func=P.OPENCOLL),Pin(num=16,name="1C",func=P.OPENCOLL)],
+    fp="Package_SO:SOIC-16_3.9x9.9mm_P1.27mm")
+
+# instances (deduplicated)
+u1 = THAT1240(ref="U1")          # line receiver
+u2 = OPA1641(ref="U2")           # Hi-Z DI buffer
+u3 = PCM5102A(ref="U3")          # DAC
+u4 = OPA1612(ref="U4")           # A = recon filter, B = summer  (shared dual)
+u5 = THAT1646(ref="U5")          # balanced driver
+u6 = ULN2003(ref="U6")           # shared relay driver
+k1, k2, k3 = TQ2SA(ref="K1"), TQ2SA(ref="K2"), TQ2SA(ref="K3")
+
+def dcp(rail):                   # 100nF decoupling helper
+    c = C(value="100nF"); rail += c[1]; c[2] += gnd
+
+# ---------------- Stage 1: balanced line receiver + protection ----------------
+def protect_bal(src, tag):
+    cblk = C(value="2.2uF", footprint="Capacitor_SMD:C_1206_3216Metric")
+    rs, rb = R(value="1k"), R(value="1Meg")
+    dp, dn = D(value="1N4148WS"), D(value="1N4148WS")
+    node = Net(tag)
+    src += cblk[1]; cblk[2] += rs[1]; rs[2] += node
+    rb[1] += node; rb[2] += gnd
+    dp[1] += p15; dp[2] += node      # Device:D pin1=K,pin2=A : high clamp
+    dn[1] += node; dn[2] += n15      # low clamp
+    return node
+u1["IN+"] += protect_bal(rx_hot_in, "RXIN_P")   # hot comes from the select relay (NC)
+u1["IN-"] += protect_bal(ain_cold,  "RXIN_N")   # cold is the ring (direct)
+u1["REF"] += gnd; u1["SENSE"] += rx_out; u1["OUT"] += rx_out
+u1["V+"] += p15; u1["V-"] += n15; dcp(p15); dcp(n15)
+
+# ---------------- Stage 1b: Hi-Z DI buffer (OPA1641) ----------------
+cblk = C(value="100nF", footprint="Capacitor_SMD:C_1206_3216Metric")
+rbias = R(value="1Meg"); dp, dn = D(value="1N4148WS"), D(value="1N4148WS")
+di_node = Net("DI_NODE")
+di_in += cblk[1]; cblk[2] += di_node
+rbias[1] += di_node; rbias[2] += gnd
+dp[1] += p15; dp[2] += di_node
+dn[1] += di_node; dn[2] += n15
+u2["+IN"] += di_node
+rf2, rg2 = R(value="3k"), R(value="1k")          # +12 dB
+u2["OUT"] += di_out
+rf2[1] += di_out; rf2[2] += u2["-IN"]
+rg2[1] += u2["-IN"]; rg2[2] += gnd
+u2["V+"] += p15; u2["V-"] += n15; dcp(p15); dcp(n15)
+
+# ---------------- Stage 1b: select relay K1 ----------------
+k1["P1_COM"] += ain_hot; k1["P1_NC"] += rx_hot_in; k1["P1_NO"] += di_in   # route tip
+k1["P2_COM"] += stage1_out; k1["P2_NC"] += rx_out; k1["P2_NO"] += di_out  # select output
+k1["COIL_A"] += p5; k1["COIL_B"] += k1_drv
+
+# ---------------- Stage 2: PCM5102A DAC ----------------
+for pin in ("AVDD","CPVDD","DVDD"): u3[pin] += p3v3
+for pin in ("AGND","DGND","CPGND"): u3[pin] += gnd
+for pin in ("AVDD","CPVDD","DVDD"):
+    c = C(value="100nF"); u3[pin] += c[1]; c[2] += gnd
+cb = C(value="10uF", footprint="Capacitor_SMD:C_1206_3216Metric"); u3["AVDD"] += cb[1]; cb[2] += gnd
+cfly = C(value="2.2uF"); u3["CAPP"] += cfly[1]; u3["CAPM"] += cfly[2]
+cvneg = C(value="2.2uF"); u3["VNEG"] += cvneg[1]; cvneg[2] += gnd
+cldoo = C(value="1uF"); u3["LDOO"] += cldoo[1]; cldoo[2] += gnd
+u3["DEMP"] += gnd; u3["FLT"] += gnd; u3["FMT"] += gnd
+u3["XSMT"] += dac_xsmt; rpu = R(value="10k"); dac_xsmt += rpu[1]; rpu[2] += p3v3
+u3["SCK"] += mclk; u3["BCK"] += i2s_bck; u3["DIN"] += i2s_din; u3["LRCK"] += i2s_lrck
+rload = R(value="2.2k"); u3["OUTR"] += rload[1]; rload[2] += gnd
+
+# ---------------- Stage 2: reconstruction filter = OPA1612 section A ----------------
+r1, r2 = R(value="1.5k"), R(value="1.5k"); ca = C(value="2.2nF"); cbq = C(value="1nF")
+rcA = Net("RC_A")
+u3["OUTL"] += r1[1]; r1[2] += rcA
+r2[1] += rcA; r2[2] += u4["+INA"]
+ca[1] += rcA; ca[2] += u4["OUTA"]
+cbq[1] += u4["+INA"]; cbq[2] += gnd
+u4["-INA"] += u4["OUTA"]; u4["OUTA"] += click_out
+u4["V+"] += p15; u4["V-"] += n15; dcp(p15); dcp(n15)
+
+# ---------------- Stage 3: summer = OPA1612 section B (shared chip) ----------------
+ri_in, ri_clk, rf3 = R(value="10k"), R(value="10k"), R(value="10k")
+stage1_out += ri_in[1]; ri_in[2] += u4["-INB"]
+click_out  += ri_clk[1]; ri_clk[2] += u4["-INB"]
+rf3[1] += u4["-INB"]; rf3[2] += u4["OUTB"]
+u4["+INB"] += gnd; u4["OUTB"] += mix_out
+
+# ---------------- Stage 4: level trim + THAT1646 + build-out ----------------
+RV = Part("Device","R_Potentiometer", dest=TEMPLATE,
+          footprint="Potentiometer_THT:Potentiometer_Bourns_3296W_Vertical")
+rv1 = RV(value="10k", ref="RV1")
+mix_out += rv1[1]; rv1[3] += gnd; rv1[2] += u5["IN"]
+u5["SNS-"] += u5["OUT-"]; u5["SNS+"] += u5["OUT+"]; u5["GND"] += gnd
+u5["V+"] += p15; u5["V-"] += n15; dcp(p15); dcp(n15)
+rbo_h, rbo_c = R(value="47"), R(value="47")
+u5["OUT-"] += rbo_h[1]; rbo_h[2] += aout_hot     # phase-corrected: HOT<-OUT-
+u5["OUT+"] += rbo_c[1]; rbo_c[2] += aout_cold     # COLD<-OUT+
+
+# ---------------- Stage 4: mute relay K2 + ground-lift relay K3 ----------------
+k2["P1_COM"] += aout_hot;  k2["P1_NC"] += gnd      # de-energized = muted (short to gnd)
+k2["P2_COM"] += aout_cold; k2["P2_NC"] += gnd
+k2["COIL_A"] += p5; k2["COIL_B"] += k2_drv
+k3["P1_COM"] += gnd; k3["P1_NC"] += chassis        # de-energized = bonded
+rlift = R(value="100"); clift = C(value="10nF")
+rlift[1] += gnd; rlift[2] += chassis; clift[1] += gnd; clift[2] += chassis
+k3["COIL_A"] += p5; k3["COIL_B"] += k3_drv
+
+# ---------------- shared relay driver U6 (ULN2003): 3 channels ----------------
+u6["1B"] += sel_linst;  u6["1C"] += k1_drv
+u6["2B"] += mute_en;    u6["2C"] += k2_drv
+u6["3B"] += gndlift_en; u6["3C"] += k3_drv
+u6["GND"] += gnd; u6["COM"] += p5                  # flyback common to coil supply
+
+ERC()
+out = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "..", "kicad", "audio_chain.net"))
+generate_netlist(file_=out)
+print("Integrated audio netlist ->", out)

hardware/eda/circuits/stage1_input.py

@@ -0,0 +1,82 @@
+#!/usr/bin/env python3
+"""PM_K-1 audio chain - Stage 1: balanced LINE input receiver + protection (SKiDL).
+
+Code-defined schematic. Run INSIDE the EDA container:
+    cd hardware/eda && ./run.sh python3 ../eda/circuits/stage1_input.py
+Outputs ERC results + a KiCad netlist at hardware/kicad/stage1_input.net,
+which imports into Pcbnew for layout.
+
+VERIFIED against datasheets:
+  * THAT1240 = 0 dB (unity-gain) line receiver; SO-8 pinout per THAT doc 600035
+    rev 05: 1=Ref 2=In- 3=In+ 4=Vee 5=Sense 6=Vout 7=Vcc 8=NC. Supply 6-36V
+    (our +/-15V is in range). Pin-compatible 2nd sources: INA134 / SSM2141.
+  * clamp-diode orientation per KiCad Device:D (pin1=K cathode, pin2=A anode).
+Open at BOM time only: exact clamp-diode part (fast low-leakage small-signal;
+1N4148WS is a placeholder).
+"""
+import os
+from skidl import *
+
+set_default_tool(KICAD9)
+
+# ---------- passive templates ----------
+R = Part("Device", "R", dest=TEMPLATE, footprint="Resistor_SMD:R_0805_2012Metric")
+C = Part("Device", "C", dest=TEMPLATE, footprint="Capacitor_SMD:C_0805_2012Metric")
+D = Part("Device", "D", dest=TEMPLATE, footprint="Diode_SMD:D_SOD-323")
+
+# ---------- power rails (global nets; marked POWER-driven for ERC) ----------
+# No power-flag *symbols* -- they carry no footprint and SKiDL errors on that.
+# The rails arrive from the power block; here we just declare + drive them.
+p15, n15, gnd = Net("+15V"), Net("-15V"), Net("GND")
+for n in (p15, n15, gnd):
+    n.drive = POWER
+
+# ---------- THAT1240 balanced line receiver (0 dB) : pinout VERIFIED ----------
+RX = Part(name="THAT1240", tool=SKIDL, dest=TEMPLATE, ref_prefix="U",
+    footprint="Package_SO:SOIC-8_3.9x4.9mm_P1.27mm",
+    pins=[
+        Pin(num=1, name="REF",   func=Pin.types.INPUT),
+        Pin(num=2, name="IN-",   func=Pin.types.INPUT),
+        Pin(num=3, name="IN+",   func=Pin.types.INPUT),
+        Pin(num=4, name="V-",    func=Pin.types.PWRIN),
+        Pin(num=5, name="SENSE", func=Pin.types.PASSIVE),
+        Pin(num=6, name="OUT",   func=Pin.types.OUTPUT),
+        Pin(num=7, name="V+",    func=Pin.types.PWRIN),
+        Pin(num=8, name="NC",    func=Pin.types.NOCONNECT),
+    ])
+rx = RX(ref="U1")
+
+# ---------- nets ----------
+ain_hot, ain_cold, rxout = Net("AIN_HOT"), Net("AIN_COLD"), Net("RX_OUT")
+
+def protected_input(src, node_name):
+    """series DC-block cap (blocks +48V phantom) -> series R -> node;
+    bias R to gnd; clamp diodes to the +/-15V rails (orientation TODO-VERIFY)."""
+    cblk = C(value="2.2uF", footprint="Capacitor_SMD:C_1206_3216Metric")  # film
+    rs, rb = R(value="1k"), R(value="1Meg")
+    dp, dn = D(value="1N4148WS"), D(value="1N4148WS")
+    node = Net(node_name)
+    src += cblk[1]; cblk[2] += rs[1]; rs[2] += node
+    rb[1] += node; rb[2] += gnd
+    # clamp diodes: KiCad Device:D is pin1=K (cathode), pin2=A (anode).
+    dp[1] += p15; dp[2] += node      # high clamp: conducts when node > +15
+    dn[1] += node; dn[2] += n15      # low clamp:  conducts when node < -15
+    return node
+
+rx["IN+"] += protected_input(ain_hot,  "RXIN_P")
+rx["IN-"] += protected_input(ain_cold, "RXIN_N")
+rx["REF"] += gnd
+rx["SENSE"] += rxout      # sense tied to output (local feedback)
+rx["OUT"]   += rxout
+rx["V+"] += p15
+rx["V-"] += n15
+
+# supply decoupling at the receiver
+for rail in (p15, n15):
+    c = C(value="100nF")
+    rail += c[1]; c[2] += gnd
+
+ERC()
+out = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "..", "kicad", "stage1_input.net"))
+generate_netlist(file_=out)
+print("Stage 1 netlist ->", out)

hardware/eda/circuits/stage1b_select.py

@@ -0,0 +1,123 @@
+#!/usr/bin/env python3
+"""PM_K-1 audio chain - Stage 1b: Hi-Z instrument DI buffer + line/instrument select (SKiDL).
+
+Run INSIDE the EDA container:
+    cd hardware/eda && ./run.sh python3 ../eda/circuits/stage1b_select.py
+Outputs ERC + a KiCad netlist at hardware/kicad/stage1b_select.net.
+
+WHAT THIS STAGE DOES
+  The same input jack feeds either the balanced LINE receiver (Stage 1) or a Hi-Z
+  INSTRUMENT buffer (here). One DPDT relay (K1) does two jobs at once:
+    pole 1  routes the jack TIP to the line receiver (default) OR the DI buffer
+    pole 2  selects which OUTPUT (RX_OUT or DI_OUT) feeds the summing stage
+  De-energized (relay OFF) = LINE = the common case (saves coil power; fail to line).
+  The DI buffer = OPA1641 non-inverting, gain +12 dB (1+Rf/Rg), 1 Mohm input.
+
+PINOUTS VERIFIED FROM DATASHEETS
+  * OPA1641 (TI SBOS484D): 1=NC 2=-IN 3=+IN 4=V- 5=NC 6=OUT 7=V+ 8=NC. Supply +/-18V max.
+  * TQ2SA (Panasonic TQ-SMD): 2 Form C. pole1 COM=3 (throws 2,4); pole2 COM=8 (throws 7,9)
+    -- confirmed from the contact-resistance terminal pairs (2-3,3-4,7-8,8-9).
+  RESOLVED from the Panasonic TQ-SMD connection diagram (single-side-stable, top view)
+  + the contact-resistance terminal pairs (2-3,3-4,7-8,8-9):
+  * coil = pins 1 & 10 (polarity irrelevant -- non-latching single coil, no diode).
+  * pole1 COM=3, NC=4, NO=2 ; pole2 COM=8, NC=7, NO=9 ; pins 5,6 unused.
+  NC/NO sense is also firmware-correctable: the relay is GPIO-driven, so if a physical
+  unit reads opposite, invert SEL_LINST in firmware (no board change).
+  Relay coil is driven by the SHARED ULN2003 (U14) -- represented here as net K1_DRV
+  (sinks the coil) + SEL_LINST (the RP2350 GPIO). The ULN2003 is instantiated once in
+  the power/control block, not per-relay.
+"""
+import os
+from skidl import *
+
+set_default_tool(KICAD9)
+
+R = Part("Device", "R", dest=TEMPLATE, footprint="Resistor_SMD:R_0805_2012Metric")
+C = Part("Device", "C", dest=TEMPLATE, footprint="Capacitor_SMD:C_0805_2012Metric")
+D = Part("Device", "D", dest=TEMPLATE, footprint="Diode_SMD:D_SOD-323")
+
+# ---- rails ----
+p15, n15, gnd, p5 = Net("+15V"), Net("-15V"), Net("GND"), Net("+5V")
+for n in (p15, n15, gnd, p5):
+    n.drive = POWER
+
+# ---- OPA1641 JFET Hi-Z buffer (pinout verified) ----
+OPA = Part(name="OPA1641", tool=SKIDL, dest=TEMPLATE, ref_prefix="U",
+    footprint="Package_SO:SOIC-8_3.9x4.9mm_P1.27mm",
+    pins=[
+        Pin(num=1, name="NC1", func=Pin.types.NOCONNECT),
+        Pin(num=2, name="-IN", func=Pin.types.INPUT),
+        Pin(num=3, name="+IN", func=Pin.types.INPUT),
+        Pin(num=4, name="V-",  func=Pin.types.PWRIN),
+        Pin(num=5, name="NC5", func=Pin.types.NOCONNECT),
+        Pin(num=6, name="OUT", func=Pin.types.OUTPUT),
+        Pin(num=7, name="V+",  func=Pin.types.PWRIN),
+        Pin(num=8, name="NC8", func=Pin.types.NOCONNECT),
+    ])
+u = OPA(ref="U2")
+
+# ---- TQ2SA DPDT select relay (contacts verified; NC/NO + coil pins flagged) ----
+RLY = Part(name="TQ2SA-5V", tool=SKIDL, dest=TEMPLATE, ref_prefix="K",
+    footprint="Relay_SMD:Relay_DPDT_Panasonic_TQ2-SA",   # footprint: confirm at layout
+    pins=[
+        Pin(num=1,  name="COIL_A", func=Pin.types.PASSIVE),
+        Pin(num=10, name="COIL_B", func=Pin.types.PASSIVE),
+        Pin(num=3,  name="P1_COM", func=Pin.types.PASSIVE),
+        Pin(num=4,  name="P1_NC",  func=Pin.types.PASSIVE),   # de-energized = LINE
+        Pin(num=2,  name="P1_NO",  func=Pin.types.PASSIVE),   # energized = INSTRUMENT
+        Pin(num=8,  name="P2_COM", func=Pin.types.PASSIVE),
+        Pin(num=7,  name="P2_NC",  func=Pin.types.PASSIVE),
+        Pin(num=9,  name="P2_NO",  func=Pin.types.PASSIVE),
+        Pin(num=5,  name="NC5",    func=Pin.types.NOCONNECT),
+        Pin(num=6,  name="NC6",    func=Pin.types.NOCONNECT),
+    ])
+k1 = RLY(ref="K1")
+
+# ---- nets (shared with Stage 1 / Stage 3 by name) ----
+ain_hot    = Net("AIN_HOT")     # jack TIP
+rx_hot_in  = Net("RX_HOT_IN")   # -> Stage 1 line-receiver hot protection (was AIN_HOT there)
+di_in      = Net("DI_IN")       # -> this DI buffer input
+rx_out     = Net("RX_OUT")      # <- Stage 1 line receiver output
+di_out     = Net("DI_OUT")      # this DI buffer output
+stage1_out = Net("STAGE1_OUT")  # selected -> Stage 3 summing
+sel        = Net("SEL_LINST")   # RP2350 GPIO: low=LINE(default), high=INSTRUMENT
+k1_drv     = Net("K1_DRV")      # shared ULN2003 output sinks the coil
+
+# pole 1: route jack tip
+k1["P1_COM"] += ain_hot
+k1["P1_NC"]  += rx_hot_in       # default -> line receiver
+k1["P1_NO"]  += di_in           # energized -> DI buffer
+# pole 2: select output
+k1["P2_COM"] += stage1_out
+k1["P2_NC"]  += rx_out          # default -> line receiver output
+k1["P2_NO"]  += di_out          # energized -> DI buffer output
+# coil: +5V -- coil -- K1_DRV (ULN2003 sinks to gnd when SEL_LINST high)
+k1["COIL_A"] += p5
+k1["COIL_B"] += k1_drv
+
+# ---- DI buffer input: DC-block, 1M bias, rail clamps ----
+cblk = C(value="100nF", footprint="Capacitor_SMD:C_1206_3216Metric")  # film
+rbias = R(value="1Meg")
+dp, dn = D(value="1N4148WS"), D(value="1N4148WS")
+node = Net("DI_NODE")
+di_in += cblk[1]; cblk[2] += node
+rbias[1] += node; rbias[2] += gnd
+dp[1] += p15; dp[2] += node     # Device:D pin1=K, pin2=A -> high clamp (>+15)
+dn[1] += node; dn[2] += n15     # low clamp (< -15)
+u["+IN"] += node
+
+# ---- non-inverting gain: Av = 1 + Rf/Rg = 1 + 3k/1k = 4 (+12 dB) ----
+rf, rg = R(value="3k"), R(value="1k")
+u["OUT"] += di_out
+rf[1] += di_out; rf[2] += u["-IN"]
+rg[1] += u["-IN"]; rg[2] += gnd
+
+# ---- supplies + decoupling ----
+u["V+"] += p15; u["V-"] += n15
+for rail in (p15, n15):
+    c = C(value="100nF"); rail += c[1]; c[2] += gnd
+
+ERC()
+out = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "..", "kicad", "stage1b_select.net"))
+generate_netlist(file_=out)
+print("Stage 1b netlist ->", out)

hardware/eda/circuits/stage2_dac.py

@@ -0,0 +1,137 @@
+#!/usr/bin/env python3
+"""PM_K-1 audio chain - Stage 2: PCM5102A DAC + reconstruction filter (SKiDL).
+
+Run INSIDE the EDA container:
+    cd hardware/eda && ./run.sh python3 ../eda/circuits/stage2_dac.py
+Outputs ERC + a KiCad netlist at hardware/kicad/stage2_dac.net.
+
+WHAT THIS STAGE DOES
+  The RP2350 streams I2S audio (the click, and later sampled sounds) to a PCM5102A
+  DAC clocked by the dedicated low-jitter oscillator (SCK=MCLK). The PCM5102A puts
+  out 2.1 Vrms GROUND-CENTERED analog (no DC-block cap needed). A 2nd-order
+  Sallen-Key low-pass (~75 kHz, one OPA1612 section) removes the delta-sigma HF
+  residue before the click reaches the summing/output stages -> CLICK_OUT.
+
+PINOUTS VERIFIED FROM DATASHEETS
+  * PCM5102A (TI SLAS859C, PW/TSSOP-20): pin map below matches the datasheet table.
+    Output 2.1Vrms GND-centered; 3.3V supplies; charge pump (CAPP/CAPM flying cap +
+    VNEG) makes the negative rail for the ground-centered swing.
+  * OPA1612 (dual): standard JEDEC dual-opamp SOIC-8 pinout
+    (1=OUTA 2=-INA 3=+INA 4=V- 5=+INB 6=-INB 7=OUTB 8=V+), confirmed against the
+    OPA164x dual on its datasheet (identical layout). Confirm OPA1612 sheet at layout.
+"""
+import os
+from skidl import *
+
+set_default_tool(KICAD9)
+
+R  = Part("Device", "R", dest=TEMPLATE, footprint="Resistor_SMD:R_0805_2012Metric")
+C  = Part("Device", "C", dest=TEMPLATE, footprint="Capacitor_SMD:C_0805_2012Metric")
+
+# ---- rails / signals ----
+p3v3, gnd, p15, n15 = Net("+3V3"), Net("GND"), Net("+15V"), Net("-15V")
+for n in (p3v3, gnd, p15, n15):
+    n.drive = POWER
+mclk   = Net("MCLK")        # low-jitter audio clock -> SCK
+i2s_bck, i2s_din, i2s_lrck = Net("I2S_BCK"), Net("I2S_DIN"), Net("I2S_LRCK")  # from RP2350
+dac_xsmt = Net("DAC_XSMT")  # GPIO soft-mute (high=unmute), pulled up
+click_out = Net("CLICK_OUT")# filtered click -> Stage 3 summing
+
+# ---- PCM5102A (pinout verified, TI SLAS859C) ----
+DAC = Part(name="PCM5102A", tool=SKIDL, dest=TEMPLATE, ref_prefix="U",
+    footprint="Package_SO:TSSOP-20_4.4x6.5mm_P0.65mm",
+    pins=[
+        Pin(num=1,  name="CPVDD", func=Pin.types.PWRIN),
+        Pin(num=2,  name="CAPP",  func=Pin.types.PASSIVE),
+        Pin(num=3,  name="CPGND", func=Pin.types.PWRIN),
+        Pin(num=4,  name="CAPM",  func=Pin.types.PASSIVE),
+        Pin(num=5,  name="VNEG",  func=Pin.types.PASSIVE),
+        Pin(num=6,  name="OUTL",  func=Pin.types.OUTPUT),
+        Pin(num=7,  name="OUTR",  func=Pin.types.OUTPUT),
+        Pin(num=8,  name="AVDD",  func=Pin.types.PWRIN),
+        Pin(num=9,  name="AGND",  func=Pin.types.PWRIN),
+        Pin(num=10, name="DEMP",  func=Pin.types.INPUT),
+        Pin(num=11, name="FLT",   func=Pin.types.INPUT),
+        Pin(num=12, name="SCK",   func=Pin.types.INPUT),
+        Pin(num=13, name="BCK",   func=Pin.types.INPUT),
+        Pin(num=14, name="DIN",   func=Pin.types.INPUT),
+        Pin(num=15, name="LRCK",  func=Pin.types.INPUT),
+        Pin(num=16, name="FMT",   func=Pin.types.INPUT),
+        Pin(num=17, name="XSMT",  func=Pin.types.INPUT),
+        Pin(num=18, name="LDOO",  func=Pin.types.PWROUT),
+        Pin(num=19, name="DGND",  func=Pin.types.PWRIN),
+        Pin(num=20, name="DVDD",  func=Pin.types.PWRIN),
+    ])
+dac = DAC(ref="U3")
+
+# ---- OPA1612 dual op-amp (standard dual pinout) ----
+OPA2 = Part(name="OPA1612", tool=SKIDL, dest=TEMPLATE, ref_prefix="U",
+    footprint="Package_SO:SOIC-8_3.9x4.9mm_P1.27mm",
+    pins=[
+        Pin(num=1, name="OUTA", func=Pin.types.OUTPUT),
+        Pin(num=2, name="-INA", func=Pin.types.INPUT),
+        Pin(num=3, name="+INA", func=Pin.types.INPUT),
+        Pin(num=4, name="V-",   func=Pin.types.PWRIN),
+        Pin(num=5, name="+INB", func=Pin.types.INPUT),
+        Pin(num=6, name="-INB", func=Pin.types.INPUT),
+        Pin(num=7, name="OUTB", func=Pin.types.OUTPUT),
+        Pin(num=8, name="V+",   func=Pin.types.PWRIN),
+    ])
+flt = OPA2(ref="U4")
+
+# ---- PCM5102A supplies + grounds (all grounds tied; <0.2V per datasheet) ----
+dac["AVDD"]  += p3v3
+dac["CPVDD"] += p3v3
+dac["DVDD"]  += p3v3
+dac["AGND"]  += gnd
+dac["DGND"]  += gnd
+dac["CPGND"] += gnd
+for pin in ("AVDD", "CPVDD", "DVDD"):
+    c = C(value="100nF"); dac[pin] += c[1]; c[2] += gnd
+cbulk = C(value="10uF", footprint="Capacitor_SMD:C_1206_3216Metric")
+dac["AVDD"] += cbulk[1]; cbulk[2] += gnd
+
+# charge pump: flying cap across CAPP/CAPM, VNEG + LDOO decoupling
+cfly = C(value="2.2uF", footprint="Capacitor_SMD:C_0805_2012Metric")
+dac["CAPP"] += cfly[1]; dac["CAPM"] += cfly[2]
+cvneg = C(value="2.2uF"); dac["VNEG"] += cvneg[1]; cvneg[2] += gnd
+cldoo = C(value="1uF");   dac["LDOO"] += cldoo[1]; cldoo[2] += gnd
+
+# control-pin tie-offs: no de-emphasis, normal latency, I2S format
+dac["DEMP"] += gnd
+dac["FLT"]  += gnd
+dac["FMT"]  += gnd
+# soft-mute: GPIO with 10k pull-up to keep un-muted by default
+dac["XSMT"] += dac_xsmt
+rpull = R(value="10k"); dac_xsmt += rpull[1]; rpull[2] += p3v3
+
+# clocks + data
+dac["SCK"]  += mclk
+dac["BCK"]  += i2s_bck
+dac["DIN"]  += i2s_din
+dac["LRCK"] += i2s_lrck
+
+# OUTR unused (mono click on L): give it the datasheet-recommended load
+rload = R(value="2.2k"); dac["OUTR"] += rload[1]; rload[2] += gnd
+
+# ---- Sallen-Key reconstruction LPF on OUTL (R=1.5k, Ca=2.2n, Cb=1n ~75kHz) ----
+r1, r2 = R(value="1.5k"), R(value="1.5k")
+ca = C(value="2.2nF"); cb = C(value="1nF")
+nodeA = Net("RC_A")
+dac["OUTL"] += r1[1]; r1[2] += nodeA
+r2[1] += nodeA; r2[2] += flt["+INA"]
+ca[1] += nodeA; ca[2] += flt["OUTA"]       # feedback cap
+cb[1] += flt["+INA"]; cb[2] += gnd
+flt["-INA"] += flt["OUTA"]                 # unity-gain follower
+flt["OUTA"] += click_out
+
+# ---- OPA1612 supplies + decoupling; park unused section B ----
+flt["V+"] += p15; flt["V-"] += n15
+for rail in (p15, n15):
+    c = C(value="100nF"); rail += c[1]; c[2] += gnd
+flt["+INB"] += gnd; flt["OUTB"] += flt["-INB"]   # B = grounded follower (parked)
+
+ERC()
+out = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "..", "kicad", "stage2_dac.net"))
+generate_netlist(file_=out)
+print("Stage 2 netlist ->", out)

hardware/eda/circuits/stage3_sum.py

@@ -0,0 +1,69 @@
+#!/usr/bin/env python3
+"""PM_K-1 audio chain - Stage 3: summing node (selected input + click) (SKiDL).
+
+Run INSIDE the EDA container:
+    cd hardware/eda && ./run.sh python3 ../eda/circuits/stage3_sum.py
+Outputs ERC + a KiCad netlist at hardware/kicad/stage3_sum.net.
+
+WHAT THIS STAGE DOES
+  Inverting summing amp (OPA1612 section) mixes STAGE1_OUT (the line/instrument input,
+  unity) and CLICK_OUT (the filtered DAC click). Each source enters through its own
+  10k resistor into the op-amp's virtual-ground node, so the two never interact. The
+  "digital mix" lives upstream: click level is set by the DAC; the input passes at
+  unity. Output MIX_OUT -> Stage 4 balanced driver.
+    Vout = -(STAGE1_OUT + CLICK_OUT)   (Rf = Ri = 10k)
+
+  POLARITY: an inverting summer flips phase. That is corrected for free at the Stage 4
+  balanced driver by assigning hot/cold accordingly (absolute polarity preserved).
+
+  OPA1612 dual: standard JEDEC pinout (1=OUTA 2=-INA 3=+INA 4=V- 5=+INB 6=-INB 7=OUTB
+  8=V+). At INTEGRATION this summer can use the PARKED 2nd half of the Stage 2 filter's
+  OPA1612 (U4) instead of a separate package -- noted for the merge step.
+"""
+import os
+from skidl import *
+
+set_default_tool(KICAD9)
+
+R = Part("Device", "R", dest=TEMPLATE, footprint="Resistor_SMD:R_0805_2012Metric")
+C = Part("Device", "C", dest=TEMPLATE, footprint="Capacitor_SMD:C_0805_2012Metric")
+
+p15, n15, gnd = Net("+15V"), Net("-15V"), Net("GND")
+for n in (p15, n15, gnd):
+    n.drive = POWER
+stage1_out = Net("STAGE1_OUT")   # from Stage 1b relay (selected input)
+click_out  = Net("CLICK_OUT")    # from Stage 2 reconstruction filter
+mix_out    = Net("MIX_OUT")      # -> Stage 4 balanced driver
+
+OPA2 = Part(name="OPA1612", tool=SKIDL, dest=TEMPLATE, ref_prefix="U",
+    footprint="Package_SO:SOIC-8_3.9x4.9mm_P1.27mm",
+    pins=[
+        Pin(num=1, name="OUTA", func=Pin.types.OUTPUT),
+        Pin(num=2, name="-INA", func=Pin.types.INPUT),
+        Pin(num=3, name="+INA", func=Pin.types.INPUT),
+        Pin(num=4, name="V-",   func=Pin.types.PWRIN),
+        Pin(num=5, name="+INB", func=Pin.types.INPUT),
+        Pin(num=6, name="-INB", func=Pin.types.INPUT),
+        Pin(num=7, name="OUTB", func=Pin.types.OUTPUT),
+        Pin(num=8, name="V+",   func=Pin.types.PWRIN),
+    ])
+u = OPA2(ref="U5")
+
+# inverting summer: each source -> 10k -> virtual-ground (-INA); Rf 10k; +INA -> gnd
+ri_in, ri_clk, rf = R(value="10k"), R(value="10k"), R(value="10k")
+stage1_out += ri_in[1];  ri_in[2]  += u["-INA"]
+click_out  += ri_clk[1]; ri_clk[2] += u["-INA"]
+rf[1] += u["-INA"]; rf[2] += u["OUTA"]
+u["+INA"] += gnd
+u["OUTA"] += mix_out
+
+# supplies + decoupling; park unused section B
+u["V+"] += p15; u["V-"] += n15
+for rail in (p15, n15):
+    c = C(value="100nF"); rail += c[1]; c[2] += gnd
+u["+INB"] += gnd; u["OUTB"] += u["-INB"]   # parked follower
+
+ERC()
+out = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "..", "kicad", "stage3_sum.net"))
+generate_netlist(file_=out)
+print("Stage 3 netlist ->", out)

hardware/eda/circuits/stage4_driver.py

@@ -0,0 +1,113 @@
+#!/usr/bin/env python3
+"""PM_K-1 audio chain - Stage 4: balanced output driver (THAT1646) + mute + ground-lift.
+
+Run INSIDE the EDA container:
+    cd hardware/eda && ./run.sh python3 ../eda/circuits/stage4_driver.py
+Outputs ERC + a KiCad netlist at hardware/kicad/stage4_driver.net. This closes the
+audio chain: MIX_OUT -> level trim -> THAT1646 -> build-out -> mute relay -> balanced
+output on the analog interconnect; plus the ground-lift relay.
+
+PINOUT VERIFIED (THAT doc 600078 rev 07, SO-8):
+  THAT1646: 1=Out- 2=Sns- 3=Gnd 4=In 5=Vee(V-) 6=Vcc(V+) 7=Sns+ 8=Out+.
+  Fixed +6 dB differential gain; sense pins tie to the output pins (local sense) with
+  the 47 ohm build-out OUTSIDE the loop for cable stability. Supply 4-18V (we use +/-15).
+  TQ2SA relay pinout per stage1b (coil 1/10; pole1 COM=3 NC=4 NO=2; pole2 COM=8 NC=7 NO=9).
+
+KEY CHOICES
+  * Level cal: the THAT1646 gain is FIXED (+6 dB), so the calibration trim is a 25-turn
+    pot ahead of it (DAC full-scale -> +4 dBu, accounting for summer + the +6 dB).
+  * Phase: Stage 3's summer inverted the signal; corrected here by taking AOUT_HOT from
+    Out- and AOUT_COLD from Out+ (absolute polarity preserved).
+  * Mute (K2): fail-safe -- de-energized shorts both legs to GND (after the 47 ohm
+    build-out, so the driver is current-limited). Energized = un-muted. Driven by the
+    hardware rail-supervisor via K2_DRV (in the power block); MCU can also assert.
+  * Ground-lift (K3): de-energized = bonded (GND<->CHASSIS); energize to LIFT. Soft-lift
+    100 ohm || 10 nF across the contact keeps an RF/safety path. A face panel switch sits
+    in series downstream (CHASSIS pin on the interconnect) -> both-must-close to bond.
+"""
+import os
+from skidl import *
+
+set_default_tool(KICAD9)
+
+R = Part("Device", "R", dest=TEMPLATE, footprint="Resistor_SMD:R_0805_2012Metric")
+C = Part("Device", "C", dest=TEMPLATE, footprint="Capacitor_SMD:C_0805_2012Metric")
+
+p15, n15, gnd, p5 = Net("+15V"), Net("-15V"), Net("GND"), Net("+5V")
+for n in (p15, n15, gnd, p5):
+    n.drive = POWER
+mix_out  = Net("MIX_OUT")        # from Stage 3 summer (inverted)
+aout_hot, aout_cold = Net("AOUT_HOT"), Net("AOUT_COLD")  # -> analog interconnect
+chassis  = Net("CHASSIS")        # shield -> interconnect (face panel switch + chassis)
+k2_drv, k3_drv = Net("K2_DRV"), Net("K3_DRV")            # relay coil drives
+
+# ---- THAT1646 balanced line driver (pinout verified) ----
+DRV = Part(name="THAT1646", tool=SKIDL, dest=TEMPLATE, ref_prefix="U",
+    footprint="Package_SO:SOIC-8_3.9x4.9mm_P1.27mm",
+    pins=[
+        Pin(num=1, name="OUT-", func=Pin.types.OUTPUT),
+        Pin(num=2, name="SNS-", func=Pin.types.INPUT),
+        Pin(num=3, name="GND",  func=Pin.types.PWRIN),
+        Pin(num=4, name="IN",   func=Pin.types.INPUT),
+        Pin(num=5, name="V-",   func=Pin.types.PWRIN),
+        Pin(num=6, name="V+",   func=Pin.types.PWRIN),
+        Pin(num=7, name="SNS+", func=Pin.types.INPUT),
+        Pin(num=8, name="OUT+", func=Pin.types.OUTPUT),
+    ])
+drv = DRV(ref="U6")
+
+# ---- TQ2SA relay (verified pinout, reused def) ----
+def tq2sa(ref):
+    p = Part(name="TQ2SA-5V", tool=SKIDL, dest=TEMPLATE, ref_prefix="K",
+        footprint="Relay_SMD:Relay_DPDT_Panasonic_TQ2-SA",
+        pins=[
+            Pin(num=1,  name="COIL_A", func=Pin.types.PASSIVE),
+            Pin(num=10, name="COIL_B", func=Pin.types.PASSIVE),
+            Pin(num=3,  name="P1_COM", func=Pin.types.PASSIVE),
+            Pin(num=4,  name="P1_NC",  func=Pin.types.PASSIVE),
+            Pin(num=2,  name="P1_NO",  func=Pin.types.PASSIVE),
+            Pin(num=8,  name="P2_COM", func=Pin.types.PASSIVE),
+            Pin(num=7,  name="P2_NC",  func=Pin.types.PASSIVE),
+            Pin(num=9,  name="P2_NO",  func=Pin.types.PASSIVE),
+            Pin(num=5,  name="NC5",    func=Pin.types.NOCONNECT),
+            Pin(num=6,  name="NC6",    func=Pin.types.NOCONNECT),
+        ])
+    return p(ref=ref)
+k2 = tq2sa("K2")   # mute
+k3 = tq2sa("K3")   # ground-lift
+
+# ---- level-cal trim (25-turn pot): MIX_OUT (top) / GND (bottom) / wiper -> THAT1646 IN ----
+RV = Part("Device", "R_Potentiometer", dest=TEMPLATE,
+          footprint="Potentiometer_THT:Potentiometer_Bourns_3296W_Vertical")
+rv1 = RV(value="10k", ref="RV1")
+mix_out += rv1[1]; rv1[3] += gnd; rv1[2] += drv["IN"]
+
+# ---- THAT1646: sense ties (local) + supplies ----
+drv["SNS-"] += drv["OUT-"]
+drv["SNS+"] += drv["OUT+"]
+drv["GND"]  += gnd
+drv["V+"] += p15; drv["V-"] += n15
+for rail in (p15, n15):
+    c = C(value="100nF"); rail += c[1]; c[2] += gnd
+
+# ---- 47 ohm build-out (phase-corrected: HOT<-OUT-, COLD<-OUT+) ----
+rbo_h, rbo_c = R(value="47"), R(value="47")
+drv["OUT-"] += rbo_h[1]; rbo_h[2] += aout_hot
+drv["OUT+"] += rbo_c[1]; rbo_c[2] += aout_cold
+
+# ---- mute relay K2: de-energized shorts both legs to GND (fail-safe) ----
+k2["P1_COM"] += aout_hot;  k2["P1_NC"] += gnd      # de-energized: hot -> GND (muted)
+k2["P2_COM"] += aout_cold; k2["P2_NC"] += gnd      # de-energized: cold -> GND
+k2["COIL_A"] += p5; k2["COIL_B"] += k2_drv         # energize (rails OK) = un-mute
+
+# ---- ground-lift K3: de-energized bonds GND<->CHASSIS; energize to lift ----
+k3["P1_COM"] += gnd; k3["P1_NC"] += chassis        # de-energized: bonded
+rlift = R(value="100"); clift = C(value="10nF")
+gnd += rlift[1]; rlift[2] += chassis               # soft-lift: 100 ohm || 10 nF
+clift[1] += gnd; clift[2] += chassis
+k3["COIL_A"] += p5; k3["COIL_B"] += k3_drv
+
+ERC()
+out = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "..", "kicad", "stage4_driver.net"))
+generate_netlist(file_=out)
+print("Stage 4 netlist ->", out)

hardware/eda/run.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+# Build (first time) and run the PM_K-1 EDA container with the repo mounted.
+#
+#   ./run.sh                 # interactive shell in hardware/kicad/
+#   ./run.sh kicad-cli sch erc pm_k1_core.kicad_sch
+#   ./run.sh ngspice -b sim/some.cir
+#
+# Override the runtime with RUNTIME=docker ./run.sh ...
+set -euo pipefail
+
+IMG="pmk1-eda:9.0"
+EDA_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"   # hardware/eda
+REPO_DIR="$(cd "$EDA_DIR/../.." && pwd)"                  # repo root
+RUNTIME="${RUNTIME:-podman}"
+
+if ! "$RUNTIME" image inspect "$IMG" >/dev/null 2>&1; then
+  echo ">> building $IMG (first run, a few minutes)…" >&2
+  "$RUNTIME" build -t "$IMG" "$EDA_DIR"
+fi
+
+# Mount the whole repo so KiCad/ngspice see hardware/ ; land in hardware/kicad.
+flags=(--rm -v "$REPO_DIR":/work:Z -w /work/hardware/kicad)
+[[ -t 0 && $# -eq 0 ]] && flags+=(-it)
+exec "$RUNTIME" run "${flags[@]}" "$IMG" "${@:-bash}"

hardware/eda/sim/.gitignore

@@ -0,0 +1 @@
+*.csv

hardware/eda/sim/input_loading.cir

@@ -0,0 +1,47 @@
+* PM_K-1 : input loading -- line receiver (25k) vs Hi-Z instrument buffer (1M)
+*
+* This is the circuit-level proof of a decision we made by hand: why a guitar/bass
+* needs a HIGH-impedance input. A passive pickup is inductive, so the load impedance
+* it sees shapes its tone. Plug it into a low impedance and you damp its resonance
+* and lose treble + level; a high-Z buffer preserves it.
+*
+* Pickup model: open-circuit source + winding resistance + inductance + self-capacitance.
+* Plus a typical ~300 pF guitar cable. We drive two identical pickup+cable networks
+* from one ideal source and load them differently, then compare.
+*
+* Run:  ngspice -b sim/input_loading.cir   (from inside the EDA container)
+
+.title PM_K-1 input loading: line 25k vs instrument 1M
+
+Vpu  src 0 AC 1
+
+* --- Branch A: LINE input, ~25k receiver impedance ---
+RdcA  src a1 6k
+LpuA  a1  a2 3
+CpuA  a2  0  150p
+CcabA a2  0  300p
+RinA  a2  0  25k
+
+* --- Branch B: INSTRUMENT input, 1M Hi-Z buffer ---
+RdcB  src b1 6k
+LpuB  b1  b2 3
+CpuB  b2  0  150p
+CcabB b2  0  300p
+RinB  b2  0  1meg
+
+.ac dec 100 10 100k
+
+.control
+run
+meas ac a_1k  find vdb(a2) at=1000
+meas ac b_1k  find vdb(b2) at=1000
+meas ac a_peak max vdb(a2) from=1000 to=20000
+meas ac b_peak max vdb(b2) from=1000 to=20000
+echo
+echo "  Level @1kHz   : line(25k)= $&a_1k dB   inst(1M)= $&b_1k dB"
+echo "  Resonant peak : line(25k)= $&a_peak dB   inst(1M)= $&b_peak dB"
+echo "  -> the 25k load drags the signal down and flattens the pickup's natural peak;"
+echo "     the 1M input preserves level and tone. Hence the switchable Hi-Z front end."
+wrdata ../eda/sim/input_loading.csv vdb(a2) vdb(b2)
+.endc
+.end

hardware/eda/sim/stage1_cmrr.cir

@@ -0,0 +1,56 @@
+* PM_K-1 Stage 1 : balanced line receiver -- why CMRR needs matched resistors
+*
+* A balanced receiver rejects "common-mode" noise -- hum/interference that appears
+* equally on both signal wires -- by SUBTRACTING the two wires. How well it cancels
+* (its Common-Mode Rejection Ratio, CMRR) depends entirely on how well its four
+* resistors match. This is the circuit-level reason we chose the laser-trimmed
+* THAT1240 instead of a discrete op-amp + four 1% resistors.
+*
+* Three identical unity-gain difference amplifiers, driven common-mode (same 1V on
+* both inputs), with 0% / 0.1% / 1% mismatch on one resistor.
+* CMRR(dB) = -20*log10(|Vout|)  since differential gain = 1 and Vcm = 1V.
+*
+* Run:  ngspice -b ../eda/sim/stage1_cmrr.cir
+
+.title Stage1 line receiver CMRR vs resistor match
+
+Vcm cm 0 AC 1            ; common-mode drive: both inputs tied to cm
+
+* ---- A: perfectly matched ----
+EA outa 0 vpa vma 1e6
+R1a cm   vma 10k
+R2a outa vma 10k
+R3a cm   vpa 10k
+R4a vpa  0   10k
+
+* ---- B: 0.1% mismatch on one resistor ----
+EB outb 0 vpb vmb 1e6
+R1b cm   vmb 10k
+R2b outb vmb 10k
+R3b cm   vpb 10k
+R4b vpb  0   10.01k
+
+* ---- C: 1% mismatch on one resistor ----
+EC outc 0 vpc vmc 1e6
+R1c cm   vmc 10k
+R2c outc vmc 10k
+R3c cm   vpc 10k
+R4c vpc  0   10.1k
+
+.ac dec 10 100 10k
+.control
+run
+meas ac acm_a find vm(outa) at=1000
+meas ac acm_b find vm(outb) at=1000
+meas ac acm_c find vm(outc) at=1000
+let cmrr_a = -20*log10(acm_a)
+let cmrr_b = -20*log10(acm_b)
+let cmrr_c = -20*log10(acm_c)
+echo
+echo "  CMRR  perfect match : $&cmrr_a dB   (limited only by the amplifier)"
+echo "  CMRR  0.1% mismatch : $&cmrr_b dB"
+echo "  CMRR  1%   mismatch : $&cmrr_c dB"
+echo "  -> hand-matched 1% resistors give poor rejection; the THAT1240's"
+echo "     laser-trimmed internal resistors are how we get >90 dB for free."
+.endc
+.end

hardware/eda/sim/stage1_phantom.cir

@@ -0,0 +1,39 @@
+* PM_K-1 Stage 1 : input protection -- a +48V phantom-power step at the jack
+*
+* "Phantom power" is +48V DC that mixers put on their MIC inputs. If it ever reaches
+* our input (miswire, wrong cable, our OUT plugged into a phantom'd input), a bare
+* op-amp input would die. Our protection makes it a non-event:
+*   - a series DC-BLOCKING film cap passes audio (AC) but blocks the +48V (DC),
+*   - a series resistor + clamp diodes to the +/-15V rails survive the turn-on EDGE
+*     (the cap passes the fast step before it charges).
+*
+* We hit the input with a +48V step at t=1ms and watch the OP-AMP INPUT node.
+*
+* Run:  ngspice -b ../eda/sim/stage1_phantom.cir
+
+.title Stage1 phantom protection
+
+Vin in 0 PWL(0 0 1m 0 1.001m 48 5 48)   ; +48V appears at t=1ms, stays
+
+C1  in a 1u            ; DC-blocking film cap (audio passes, DC blocked)
+Rs  a  n 1k            ; series current limit
+Rb  n  0 1meg          ; bias / input impedance (audio high-pass corner ~0.16 Hz)
+
+.model Dclamp D(Is=1e-14 N=1 Rs=10)
+Dp n  vp Dclamp        ; clamp to +15
+Dn vn n  Dclamp        ; clamp to -15
+Vp vp 0 15
+Vn vn 0 -15
+
+.tran 2m 5
+.control
+run
+meas tran vn_peak  max v(n) from=1m to=5
+meas tran vn_final find v(n) at=4.9
+echo
+echo "  op-amp input PEAK during the +48V step : $&vn_peak V   (clamped near a +/-15 rail)"
+echo "  op-amp input STEADY-STATE              : $&vn_final V   (DC blocked by the cap)"
+echo "  -> +48V at the jack becomes a clamped blip that decays to ~0. Nothing is harmed;"
+echo "     a wrong patch only ever sounds wrong. (Audio passes -- the high-pass is ~0.16 Hz.)"
+.endc
+.end

hardware/eda/sim/stage1b_di.cir

@@ -0,0 +1,28 @@
+* PM_K-1 Stage 1b : Hi-Z instrument DI buffer -- gain + flatness check
+*
+* An OPA1641 (JFET input, ~1e12 ohm) as a non-inverting amp. The INPUT impedance
+* the instrument sees is set by the bias resistor (1 Mohm) -- which the earlier
+* input_loading.cir proved is what preserves a pickup's tone. Here we just confirm
+* the voltage gain:  Av = 1 + Rf/Rg.  Target +12 dB (x4) with Rf=3k, Rg=1k.
+*
+* Run:  ngspice -b ../eda/sim/stage1b_di.cir
+
+.title Stage1b DI buffer gain
+
+Vin in 0 AC 1
+Eop out 0 in vm 1e6     ; ideal op-amp: +IN = in, -IN = vm
+Rf  out vm 3k           ; feedback
+Rg  vm  0  1k           ; gain set
+
+.ac dec 20 10 100k
+.control
+run
+meas ac g_1k   find vdb(out) at=1000
+meas ac g_20k  find vdb(out) at=20000
+let av = pow(10, g_1k/20)
+echo
+echo "  DI buffer gain @1kHz  : $&g_1k dB   ( x$&av )   target +12.04 dB (x4)"
+echo "  DI buffer gain @20kHz : $&g_20k dB  (flat across audio band)"
+echo "  Input impedance is set by the 1Mohm bias R (JFET input ~1e12 ohm) -- see input_loading.cir"
+.endc
+.end

hardware/eda/sim/stage2_recon.cir

@@ -0,0 +1,35 @@
+* PM_K-1 Stage 2 : DAC reconstruction filter (2nd-order Sallen-Key low-pass)
+*
+* The PCM5102A is a delta-sigma DAC: its analog output carries the audio plus
+* shaped high-frequency quantization noise WAY above the audio band. A gentle
+* low-pass cleans that residue before it reaches the pro output stage. We want it
+* dead flat to 20 kHz and rolling off above ~80 kHz (Butterworth, Q~0.7).
+*
+* Unity-gain Sallen-Key, equal R. Target fc ~75 kHz with R=1.5k, C1=2.2n, C2=1n.
+* Run:  ngspice -b ../eda/sim/stage2_recon.cir
+
+.title Stage2 DAC reconstruction filter
+
+.param R=1.5k
+.param Ca=2.2n
+.param Cb=1n
+
+Vin in 0 AC 1
+R1 in a   {R}
+R2 a  vp  {R}
+Ca a  out {Ca}      ; feedback cap
+Cb vp 0   {Cb}      ; cap to ground
+Eop out 0 vp out 1e6   ; unity-gain follower op-amp (-in tied to out)
+
+.ac dec 100 100 2meg
+.control
+run
+meas ac g_1k  find vdb(out) at=1k
+meas ac g_20k find vdb(out) at=20k
+meas ac f_3db when vdb(out)=-3
+echo
+echo "  passband @1kHz : $&g_1k dB"
+echo "  @20kHz (audio edge) : $&g_20k dB   (want ~0 dB = flat)"
+echo "  -3dB corner : $&f_3db Hz   (well above audio; attenuates DAC HF residue)"
+.endc
+.end

hardware/eda/sim/stage3_sum.cir

@@ -0,0 +1,40 @@
+* PM_K-1 Stage 3 : summing node (selected input + click)
+*
+* An inverting summing amp mixes STAGE1_OUT (line/instrument) and CLICK_OUT (DAC).
+* Each source feeds the op-amp's inverting input through its own 10k resistor; the
+* feedback holds that node at a "virtual ground" (~0V). Because BOTH sources see 0V
+* there, neither can load or pull on the other -- they sum with no interaction.
+*   Vout = -(Rf/Ri1)*V1 - (Rf/Ri2)*V2 ;  with Rf=Ri=10k -> Vout = -(V1+V2).
+*
+* We confirm: each input alone = 0 dB (gain -1), both together = +6 dB (they add),
+* and each input's gain is unchanged by the other (isolation).
+* Run:  ngspice -b ../eda/sim/stage3_sum.cir
+
+.title Stage3 inverting summer
+
+Vinp inp 0 AC 1        ; selected input (STAGE1_OUT)
+Vclk clk 0 AC 1        ; filtered click (CLICK_OUT)
+Ri1 inp vm 10k
+Ri2 clk vm 10k
+Rf  vm  out 10k
+Eop out 0 0 vm 1e6     ; +in = gnd, -in = vm  -> inverting; feedback makes vm a virtual ground
+
+.ac dec 10 100 20k
+.control
+* both sources active -> they sum
+run
+meas ac g_both find vdb(out) at=1k
+echo "  both        = $&g_both dB   (+6 dB over each-alone = the two sum)"
+* input alone (click muted)
+alter @Vclk[acmag]=0
+run
+meas ac g_in find vdb(out) at=1k
+echo "  input alone = $&g_in dB    (gain -1, i.e. 0 dB)"
+* click alone (input muted)
+alter @Vinp[acmag]=0
+alter @Vclk[acmag]=1
+run
+meas ac g_clk find vdb(out) at=1k
+echo "  click alone = $&g_clk dB    (gain -1; unchanged by the input = virtual-ground isolation)"
+.endc
+.end

hardware/eda/sim/stage4_driver.cir

@@ -0,0 +1,38 @@
+* PM_K-1 Stage 4 : balanced output driver -- antiphase + build-out into a cable
+*
+* The THAT1646 turns the single-ended mix into a balanced (differential) output:
+* Out+ and Out- swing equal-and-opposite, so noise picked up equally on both wires
+* cancels at the far end. It has a fixed +6 dB gain (differential = 2x input).
+* We model it as two ideal sources (Out+ = +Vin, Out- = -Vin) and add the 47 ohm
+* per-leg build-out resistors driving a 600 ohm load plus cable capacitance.
+*
+* Shows: audio band is dead flat, and the build-out + cable rolloff sits far above
+* audio -- i.e. the build-out tames long/capacitive cables without dulling the sound.
+* Run:  ngspice -b ../eda/sim/stage4_driver.cir
+
+.title Stage4 balanced driver
+
+Vin in 0 AC 1
+Eop op 0 in 0 1        ; Out+ = +Vin
+Eon on 0 0 in 1        ; Out- = -Vin   -> differential (op-on) = 2*Vin = +6 dB
+Rbp op  hot  47        ; build-out, hot leg
+Rbn on  cold 47        ; build-out, cold leg
+Rl  hot cold 600       ; receiver / load
+Cch hot 0 1n           ; ~cable capacitance per leg
+Ccc cold 0 1n
+
+.ac dec 20 10 10meg
+.control
+run
+let vddb = db(v(hot) - v(cold))      ; differential magnitude in dB
+meas ac d_1k    find vddb at=1k
+meas ac d_20k   find vddb at=20k
+meas ac d_1meg  find vddb at=1meg
+meas ac ph_hot  find vp(hot)  at=1k
+meas ac ph_cold find vp(cold) at=1k
+echo
+echo "  differential @1kHz : $&d_1k dB    @20kHz : $&d_20k dB   (flat across audio)"
+echo "  hot phase: $&ph_hot rad ; cold phase: $&ph_cold rad  (~pi rad = 180 deg apart = balanced/antiphase)"
+echo "  differential @1MHz : $&d_1meg dB  (build-out+cable rolloff stays above audio)"
+.endc
+.end

hardware/kicad/.gitignore

@@ -0,0 +1,10 @@
+# KiCad generated/derived outputs
+*.pdf
+*.net
+*.svg
+*.rpt
+*-bak
+*.kicad_prl
+fp-info-cache
+~*.lck
+*.net

hardware/kicad/audio_chain.erc

@@ -0,0 +1,40 @@
+ERC WARNING: Only one pin (INPUT pin 3/3B of ULN2003A/U6) attached to net GNDLIFT_EN.
+ERC WARNING: No drivers for net GNDLIFT_EN.
+ERC WARNING: Insufficient drive current on net GNDLIFT_EN for pin INPUT pin 3/3B of ULN2003A/U6.
+ERC WARNING: Only one pin (INPUT pin 15/LRCK of PCM5102A/U3) attached to net I2S_LRCK.
+ERC WARNING: No drivers for net I2S_LRCK.
+ERC WARNING: Insufficient drive current on net I2S_LRCK for pin INPUT pin 15/LRCK of PCM5102A/U3.
+ERC WARNING: Only one pin (INPUT pin 2/2B of ULN2003A/U6) attached to net MUTE_EN.
+ERC WARNING: No drivers for net MUTE_EN.
+ERC WARNING: Insufficient drive current on net MUTE_EN for pin INPUT pin 2/2B of ULN2003A/U6.
+ERC WARNING: Only one pin (INPUT pin 1/1B of ULN2003A/U6) attached to net SEL_LINST.
+ERC WARNING: No drivers for net SEL_LINST.
+ERC WARNING: Insufficient drive current on net SEL_LINST for pin INPUT pin 1/1B of ULN2003A/U6.
+ERC WARNING: Only one pin (PASSIVE pin 1/~ of C/C2) attached to net AIN_COLD.
+ERC WARNING: Only one pin (INPUT pin 14/DIN of PCM5102A/U3) attached to net I2S_DIN.
+ERC WARNING: No drivers for net I2S_DIN.
+ERC WARNING: Insufficient drive current on net I2S_DIN for pin INPUT pin 14/DIN of PCM5102A/U3.
+ERC WARNING: Only one pin (INPUT pin 12/SCK of PCM5102A/U3) attached to net MCLK.
+ERC WARNING: No drivers for net MCLK.
+ERC WARNING: Insufficient drive current on net MCLK for pin INPUT pin 12/SCK of PCM5102A/U3.
+ERC WARNING: Only one pin (INPUT pin 13/BCK of PCM5102A/U3) attached to net I2S_BCK.
+ERC WARNING: No drivers for net I2S_BCK.
+ERC WARNING: Insufficient drive current on net I2S_BCK for pin INPUT pin 13/BCK of PCM5102A/U3.
+ERC WARNING: Only one pin (PASSIVE pin 3/P1_COM of TQ2SA-5V/K1) attached to net AIN_HOT.
+ERC WARNING: Unconnected pin: INPUT pin 4/4B of ULN2003A/U6.
+ERC WARNING: Unconnected pin: INPUT pin 5/5B of ULN2003A/U6.
+ERC WARNING: Unconnected pin: INPUT pin 6/6B of ULN2003A/U6.
+ERC WARNING: Unconnected pin: INPUT pin 7/7B of ULN2003A/U6.
+ERC WARNING: Unconnected pin: OPEN-COLLECTOR pin 10/7C of ULN2003A/U6.
+ERC WARNING: Unconnected pin: OPEN-COLLECTOR pin 11/6C of ULN2003A/U6.
+ERC WARNING: Unconnected pin: OPEN-COLLECTOR pin 12/5C of ULN2003A/U6.
+ERC WARNING: Unconnected pin: OPEN-COLLECTOR pin 13/4C of ULN2003A/U6.
+ERC WARNING: Unconnected pin: PASSIVE pin 2/P1_NO of TQ2SA-5V/K2.
+ERC WARNING: Unconnected pin: PASSIVE pin 9/P2_NO of TQ2SA-5V/K2.
+ERC WARNING: Unconnected pin: PASSIVE pin 2/P1_NO of TQ2SA-5V/K3.
+ERC WARNING: Unconnected pin: PASSIVE pin 8/P2_COM of TQ2SA-5V/K3.
+ERC WARNING: Unconnected pin: PASSIVE pin 7/P2_NC of TQ2SA-5V/K3.
+ERC WARNING: Unconnected pin: PASSIVE pin 9/P2_NO of TQ2SA-5V/K3.
+ERC INFO: 37 warnings found while running ERC.
+ERC INFO: 0 errors found while running ERC.
+

hardware/kicad/audio_chain.log

@@ -0,0 +1,119 @@
+WARNING: KICAD8_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: KICAD6_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: KICAD7_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: Missing tag on THAT1240 instantiated at /work/hardware/eda/circuits/audio_chain.py:88.
+WARNING: Random tag NaoCkmuv6F generated for THAT1240.
+WARNING: Missing tag on OPA1641 instantiated at /work/hardware/eda/circuits/audio_chain.py:89.
+WARNING: Random tag bhZEXwD6Ma generated for OPA1641.
+WARNING: Missing tag on PCM5102A instantiated at /work/hardware/eda/circuits/audio_chain.py:90.
+WARNING: Random tag GKJv8Mk9db generated for PCM5102A.
+WARNING: Missing tag on OPA1612 instantiated at /work/hardware/eda/circuits/audio_chain.py:91.
+WARNING: Random tag ZiUYdGNUpf generated for OPA1612.
+WARNING: Missing tag on THAT1646 instantiated at /work/hardware/eda/circuits/audio_chain.py:92.
+WARNING: Random tag PA94RBoDz5 generated for THAT1646.
+WARNING: Missing tag on ULN2003A instantiated at /work/hardware/eda/circuits/audio_chain.py:93.
+WARNING: Random tag 7az6rCV1b8 generated for ULN2003A.
+WARNING: Missing tag on TQ2SA-5V instantiated at /work/hardware/eda/circuits/audio_chain.py:94.
+WARNING: Random tag a5p3EKoZSh generated for TQ2SA-5V.
+WARNING: Missing tag on TQ2SA-5V instantiated at /work/hardware/eda/circuits/audio_chain.py:94.
+WARNING: Random tag nzmU2EFKQ5 generated for TQ2SA-5V.
+WARNING: Missing tag on TQ2SA-5V instantiated at /work/hardware/eda/circuits/audio_chain.py:94.
+WARNING: Random tag PvvXwCojLV generated for TQ2SA-5V.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/audio_chain.py:101.
+WARNING: Random tag 1BQDYOk7Jk generated for C.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/audio_chain.py:102.
+WARNING: Random tag VJCWjFmo15 generated for R.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/audio_chain.py:102.
+WARNING: Random tag F3pmXe3Ukl generated for R.
+WARNING: Missing tag on D instantiated at /work/hardware/eda/circuits/audio_chain.py:103.
+WARNING: Random tag GcBAEBfRsm generated for D.
+WARNING: Missing tag on D instantiated at /work/hardware/eda/circuits/audio_chain.py:103.
+WARNING: Random tag DxTLvXTPXw generated for D.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/audio_chain.py:101.
+WARNING: Random tag TbYYz7sRwg generated for C.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/audio_chain.py:102.
+WARNING: Random tag q4ANsoJP6d generated for R.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/audio_chain.py:102.
+WARNING: Random tag XafPhdShAz generated for R.
+WARNING: Missing tag on D instantiated at /work/hardware/eda/circuits/audio_chain.py:103.
+WARNING: Random tag 3Dy7kKhUuS generated for D.
+WARNING: Missing tag on D instantiated at /work/hardware/eda/circuits/audio_chain.py:103.
+WARNING: Random tag srbPiv0wDA generated for D.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/audio_chain.py:97.
+WARNING: Random tag cywPzV0BP5 generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/audio_chain.py:97.
+WARNING: Random tag ys82MNo87q generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/audio_chain.py:116.
+WARNING: Random tag GjB9TiUkLV generated for C.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/audio_chain.py:117.
+WARNING: Random tag 5d0DxRmiVK generated for R.
+WARNING: Missing tag on D instantiated at /work/hardware/eda/circuits/audio_chain.py:117.
+WARNING: Random tag UiNgHe5ZoI generated for D.
+WARNING: Missing tag on D instantiated at /work/hardware/eda/circuits/audio_chain.py:117.
+WARNING: Random tag dREXHB06LQ generated for D.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/audio_chain.py:124.
+WARNING: Random tag IzL4dTk5KE generated for R.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/audio_chain.py:124.
+WARNING: Random tag aecw3XjGu8 generated for R.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/audio_chain.py:97.
+WARNING: Random tag ZkkukzL1dw generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/audio_chain.py:97.
+WARNING: Random tag SiWPcikSTD generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/audio_chain.py:139.
+WARNING: Random tag XkEyeGCXrV generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/audio_chain.py:139.
+WARNING: Random tag KtTaLAKE12 generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/audio_chain.py:139.
+WARNING: Random tag kxLUIeU4MG generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/audio_chain.py:140.
+WARNING: Random tag G0gy3YpApr generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/audio_chain.py:141.
+WARNING: Random tag 54BIrx4GwW generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/audio_chain.py:142.
+WARNING: Random tag D2ift49ZDj generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/audio_chain.py:143.
+WARNING: Random tag 2xrRFHfzVn generated for C.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/audio_chain.py:145.
+WARNING: Random tag ciywLsI1BV generated for R.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/audio_chain.py:147.
+WARNING: Random tag iHP45ECBTV generated for R.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/audio_chain.py:150.
+WARNING: Random tag SpTEBfUSZQ generated for R.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/audio_chain.py:150.
+WARNING: Random tag GANJXVVJhX generated for R.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/audio_chain.py:150.
+WARNING: Random tag cTcBdxazGj generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/audio_chain.py:150.
+WARNING: Random tag WltiwW7vNV generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/audio_chain.py:97.
+WARNING: Random tag K76qTGXZDl generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/audio_chain.py:97.
+WARNING: Random tag qNcbyMvj04 generated for C.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/audio_chain.py:160.
+WARNING: Random tag 8Z8qBauuqJ generated for R.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/audio_chain.py:160.
+WARNING: Random tag ZvbhQbNpVf generated for R.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/audio_chain.py:160.
+WARNING: Random tag XI22X1n2tP generated for R.
+WARNING: Missing tag on R_Potentiometer instantiated at /work/hardware/eda/circuits/audio_chain.py:169.
+WARNING: Random tag joe6s3brR6 generated for R_Potentiometer.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/audio_chain.py:97.
+WARNING: Random tag MjG60k1gb_ generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/audio_chain.py:97.
+WARNING: Random tag JNrbq6C1BQ generated for C.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/audio_chain.py:173.
+WARNING: Random tag IwhpZyA9LO generated for R.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/audio_chain.py:173.
+WARNING: Random tag cWxhi7FDib generated for R.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/audio_chain.py:182.
+WARNING: Random tag GS23xEE7xZ generated for R.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/audio_chain.py:182.
+WARNING: Random tag fJUwwIBJ1g generated for C.
+WARNING: Missing tag on  instantiated at /work/hardware/kicad/<frozen importlib._bootstrap>:488.
+INFO: 113 warnings found while generating netlist.
+INFO: 0 errors found while generating netlist.
+

hardware/kicad/audio_chain_sklib.py

@@ -0,0 +1,106 @@
+from collections import defaultdict
+from skidl import Pin, Part, Alias, SchLib, SKIDL, TEMPLATE
+
+from skidl.pin import pin_types
+
+SKIDL_lib_version = '0.0.1'
+
+audio_chain = SchLib(tool=SKIDL).add_parts(*[
+        Part(**{ 'name':'THAT1240', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'THAT1240'}), 'ref_prefix':'U', 'fplist':None, 'footprint':'Package_SO:SOIC-8_3.9x4.9mm_P1.27mm', 'keywords':None, 'description':'', 'datasheet':None, 'pins':[
+            Pin(num='1',name='REF',func=pin_types.INPUT),
+            Pin(num='2',name='IN-',func=pin_types.INPUT),
+            Pin(num='3',name='IN+',func=pin_types.INPUT),
+            Pin(num='4',name='V-',func=pin_types.PWRIN),
+            Pin(num='5',name='SENSE',func=pin_types.PASSIVE),
+            Pin(num='6',name='OUT',func=pin_types.OUTPUT),
+            Pin(num='7',name='V+',func=pin_types.PWRIN),
+            Pin(num='8',name='NC',func=pin_types.NOCONNECT)] }),
+        Part(**{ 'name':'OPA1641', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'OPA1641'}), 'ref_prefix':'U', 'fplist':None, 'footprint':'Package_SO:SOIC-8_3.9x4.9mm_P1.27mm', 'keywords':None, 'description':'', 'datasheet':None, 'pins':[
+            Pin(num='1',name='NC1',func=pin_types.NOCONNECT),
+            Pin(num='2',name='-IN',func=pin_types.INPUT),
+            Pin(num='3',name='+IN',func=pin_types.INPUT),
+            Pin(num='4',name='V-',func=pin_types.PWRIN),
+            Pin(num='5',name='NC5',func=pin_types.NOCONNECT),
+            Pin(num='6',name='OUT',func=pin_types.OUTPUT),
+            Pin(num='7',name='V+',func=pin_types.PWRIN),
+            Pin(num='8',name='NC8',func=pin_types.NOCONNECT)] }),
+        Part(**{ 'name':'PCM5102A', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'PCM5102A'}), 'ref_prefix':'U', 'fplist':None, 'footprint':'Package_SO:TSSOP-20_4.4x6.5mm_P0.65mm', 'keywords':None, 'description':'', 'datasheet':None, 'pins':[
+            Pin(num='1',name='CPVDD',func=pin_types.PWRIN),
+            Pin(num='2',name='CAPP',func=pin_types.PASSIVE),
+            Pin(num='3',name='CPGND',func=pin_types.PWRIN),
+            Pin(num='4',name='CAPM',func=pin_types.PASSIVE),
+            Pin(num='5',name='VNEG',func=pin_types.PASSIVE),
+            Pin(num='6',name='OUTL',func=pin_types.OUTPUT),
+            Pin(num='7',name='OUTR',func=pin_types.OUTPUT),
+            Pin(num='8',name='AVDD',func=pin_types.PWRIN),
+            Pin(num='9',name='AGND',func=pin_types.PWRIN),
+            Pin(num='10',name='DEMP',func=pin_types.INPUT),
+            Pin(num='11',name='FLT',func=pin_types.INPUT),
+            Pin(num='12',name='SCK',func=pin_types.INPUT),
+            Pin(num='13',name='BCK',func=pin_types.INPUT),
+            Pin(num='14',name='DIN',func=pin_types.INPUT),
+            Pin(num='15',name='LRCK',func=pin_types.INPUT),
+            Pin(num='16',name='FMT',func=pin_types.INPUT),
+            Pin(num='17',name='XSMT',func=pin_types.INPUT),
+            Pin(num='18',name='LDOO',func=pin_types.PWROUT),
+            Pin(num='19',name='DGND',func=pin_types.PWRIN),
+            Pin(num='20',name='DVDD',func=pin_types.PWRIN)] }),
+        Part(**{ 'name':'OPA1612', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'OPA1612'}), 'ref_prefix':'U', 'fplist':None, 'footprint':'Package_SO:SOIC-8_3.9x4.9mm_P1.27mm', 'keywords':None, 'description':'', 'datasheet':None, 'pins':[
+            Pin(num='1',name='OUTA',func=pin_types.OUTPUT),
+            Pin(num='2',name='-INA',func=pin_types.INPUT),
+            Pin(num='3',name='+INA',func=pin_types.INPUT),
+            Pin(num='4',name='V-',func=pin_types.PWRIN),
+            Pin(num='5',name='+INB',func=pin_types.INPUT),
+            Pin(num='6',name='-INB',func=pin_types.INPUT),
+            Pin(num='7',name='OUTB',func=pin_types.OUTPUT),
+            Pin(num='8',name='V+',func=pin_types.PWRIN)] }),
+        Part(**{ 'name':'THAT1646', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'THAT1646'}), 'ref_prefix':'U', 'fplist':None, 'footprint':'Package_SO:SOIC-8_3.9x4.9mm_P1.27mm', 'keywords':None, 'description':'', 'datasheet':None, 'pins':[
+            Pin(num='1',name='OUT-',func=pin_types.OUTPUT),
+            Pin(num='2',name='SNS-',func=pin_types.INPUT),
+            Pin(num='3',name='GND',func=pin_types.PWRIN),
+            Pin(num='4',name='IN',func=pin_types.INPUT),
+            Pin(num='5',name='V-',func=pin_types.PWRIN),
+            Pin(num='6',name='V+',func=pin_types.PWRIN),
+            Pin(num='7',name='SNS+',func=pin_types.INPUT),
+            Pin(num='8',name='OUT+',func=pin_types.OUTPUT)] }),
+        Part(**{ 'name':'ULN2003A', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'ULN2003A'}), 'ref_prefix':'U', 'fplist':None, 'footprint':'Package_SO:SOIC-16_3.9x9.9mm_P1.27mm', 'keywords':None, 'description':'', 'datasheet':None, 'pins':[
+            Pin(num='1',name='1B',func=pin_types.INPUT),
+            Pin(num='2',name='2B',func=pin_types.INPUT),
+            Pin(num='3',name='3B',func=pin_types.INPUT),
+            Pin(num='4',name='4B',func=pin_types.INPUT),
+            Pin(num='5',name='5B',func=pin_types.INPUT),
+            Pin(num='6',name='6B',func=pin_types.INPUT),
+            Pin(num='7',name='7B',func=pin_types.INPUT),
+            Pin(num='8',name='GND',func=pin_types.PWRIN),
+            Pin(num='9',name='COM',func=pin_types.PWRIN),
+            Pin(num='10',name='7C',func=pin_types.OPENCOLL),
+            Pin(num='11',name='6C',func=pin_types.OPENCOLL),
+            Pin(num='12',name='5C',func=pin_types.OPENCOLL),
+            Pin(num='13',name='4C',func=pin_types.OPENCOLL),
+            Pin(num='14',name='3C',func=pin_types.OPENCOLL),
+            Pin(num='15',name='2C',func=pin_types.OPENCOLL),
+            Pin(num='16',name='1C',func=pin_types.OPENCOLL)] }),
+        Part(**{ 'name':'TQ2SA-5V', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'TQ2SA-5V'}), 'ref_prefix':'K', 'fplist':None, 'footprint':'Relay_SMD:Relay_DPDT_Panasonic_TQ2-SA', 'keywords':None, 'description':'', 'datasheet':None, 'pins':[
+            Pin(num='1',name='COIL_A',func=pin_types.PASSIVE),
+            Pin(num='10',name='COIL_B',func=pin_types.PASSIVE),
+            Pin(num='3',name='P1_COM',func=pin_types.PASSIVE),
+            Pin(num='4',name='P1_NC',func=pin_types.PASSIVE),
+            Pin(num='2',name='P1_NO',func=pin_types.PASSIVE),
+            Pin(num='8',name='P2_COM',func=pin_types.PASSIVE),
+            Pin(num='7',name='P2_NC',func=pin_types.PASSIVE),
+            Pin(num='9',name='P2_NO',func=pin_types.PASSIVE),
+            Pin(num='5',name='NC5',func=pin_types.NOCONNECT),
+            Pin(num='6',name='NC6',func=pin_types.NOCONNECT)] }),
+        Part(**{ 'name':'C', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'C'}), 'ref_prefix':'C', 'fplist':[''], 'footprint':'Capacitor_SMD:C_1206_3216Metric', 'keywords':'cap capacitor', 'description':'Unpolarized capacitor', 'datasheet':'~', 'pins':[
+            Pin(num='1',name='~',func=pin_types.PASSIVE,unit=1),
+            Pin(num='2',name='~',func=pin_types.PASSIVE,unit=1)], 'unit_defs':[] }),
+        Part(**{ 'name':'R', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'R'}), 'ref_prefix':'R', 'fplist':[''], 'footprint':'Resistor_SMD:R_0805_2012Metric', 'keywords':'R res resistor', 'description':'Resistor', 'datasheet':'~', 'pins':[
+            Pin(num='1',name='~',func=pin_types.PASSIVE,unit=1),
+            Pin(num='2',name='~',func=pin_types.PASSIVE,unit=1)], 'unit_defs':[] }),
+        Part(**{ 'name':'D', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'D'}), 'ref_prefix':'D', 'fplist':[''], 'footprint':'Diode_SMD:D_SOD-323', 'keywords':'diode', 'description':'Diode', 'datasheet':'~', 'pins':[
+            Pin(num='1',name='K',func=pin_types.PASSIVE,unit=1),
+            Pin(num='2',name='A',func=pin_types.PASSIVE,unit=1)], 'unit_defs':[] }),
+        Part(**{ 'name':'R_Potentiometer', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'R_Potentiometer'}), 'ref_prefix':'RV', 'fplist':[''], 'footprint':'Potentiometer_THT:Potentiometer_Bourns_3296W_Vertical', 'keywords':'resistor variable', 'description':'Potentiometer', 'datasheet':'~', 'pins':[
+            Pin(num='1',name='1',func=pin_types.PASSIVE,unit=1),
+            Pin(num='3',name='3',func=pin_types.PASSIVE,unit=1),
+            Pin(num='2',name='2',func=pin_types.PASSIVE,unit=1)], 'unit_defs':[] })])

hardware/kicad/pm_k1_core.kicad_pro

@@ -0,0 +1,92 @@
+{
+  "board": {
+    "design_settings": {
+      "defaults": {},
+      "rules": {},
+      "track_widths": [],
+      "via_dimensions": []
+    },
+    "layer_presets": [],
+    "viewports": []
+  },
+  "boards": [],
+  "cvpcb": {
+    "equivalence_files": []
+  },
+  "erc": {
+    "erc_exclusions": [],
+    "meta": {
+      "version": 0
+    },
+    "rule_severities": {},
+    "rule_severitiesV2": {}
+  },
+  "libraries": {
+    "pinned_footprint_libs": [],
+    "pinned_symbol_libs": []
+  },
+  "meta": {
+    "filename": "pm_k1_core.kicad_pro",
+    "version": 1
+  },
+  "net_settings": {
+    "classes": [
+      {
+        "bus_width": 12,
+        "clearance": 0.2,
+        "diff_pair_gap": 0.25,
+        "diff_pair_via_gap": 0.25,
+        "diff_pair_width": 0.2,
+        "line_style": 0,
+        "microvia_diameter": 0.3,
+        "microvia_drill": 0.1,
+        "name": "Default",
+        "pcb_color": "rgba(0, 0, 0, 0.000)",
+        "schematic_color": "rgba(0, 0, 0, 0.000)",
+        "track_width": 0.25,
+        "via_diameter": 0.8,
+        "via_drill": 0.4,
+        "wire_width": 6
+      }
+    ],
+    "meta": {
+      "version": 3
+    }
+  },
+  "pcbnew": {
+    "last_paths": {
+      "gencad": "",
+      "idf": "",
+      "netlist": "",
+      "specctra_dsn": "",
+      "step": "",
+      "vrml": ""
+    },
+    "page_layout_descr_file": ""
+  },
+  "schematic": {
+    "annotate_start_num": 0,
+    "drawing": {},
+    "legacy_lib_dir": "",
+    "legacy_lib_list": [],
+    "meta": {
+      "version": 1
+    },
+    "net_format_name": "",
+    "page_layout_descr_file": "",
+    "plot_directory": "",
+    "spice_current_sheet_as_root": false,
+    "spice_external_command": "spice \"%I\"",
+    "spice_model_current_sheet_as_root": true,
+    "spice_save_all_currents": false,
+    "subpart_first_id": 65,
+    "subpart_id_separator": 0
+  },
+  "sheets": [
+    [
+      "743b8308-6a69-48de-a6ff-2336bc6c804f",
+      ""
+    ]
+  ],
+  "text_variables": {}
+}

hardware/kicad/pm_k1_core.kicad_sch

@@ -0,0 +1,56 @@
+(kicad_sch (version 20230121) (generator eeschema)
+  (uuid 743b8308-6a69-48de-a6ff-2336bc6c804f)
+  (paper "A3")
+  (title_block
+    (title "PM_K-1 Core Board (brain) - VARASYS PolyMeter")
+    (date "2026-05-30")
+    (rev "A")
+    (company "VARASYS")
+    (comment 1 "Heirloom pro-audio modular core: RP2350 + +/-15V studio audio + balanced click-injector")
+    (comment 2 "Design-of-record canvas - see hardware/DESIGN.md. Symbol placement + wiring = interactive TODO in Eeschema.")
+  )
+  (lib_symbols)
+  (text "PM_K-1 CORE BOARD (\"brain\")\nHeirloom pro-audio modular core - design-of-record canvas.\nFull spec, BOM and interconnect pinouts: hardware/DESIGN.md + hardware/BOM.csv."
+    (at 20 18 0)
+    (effects (font (size 2.2 2.2)) (justify left top))
+    (uuid 00109097-7760-4eb7-b299-bd3f64383aab)
+  )
+  (text "POWER TREE\nUSB-C 5V -> AP2112K 3V3 (digital IO)\nRP2350 internal SMPS -> 1.1V core (ext L)\nTPS65131 dual boost/inverter -> raw +/-18V\nTPS7A4901 / TPS7A3001 LDO -> CLEAN +/-15V (audio)\nStar ground; switcher in a guarded corner."
+    (at 20 45 0)
+    (effects (font (size 1.6 1.6)) (justify left top))
+    (uuid 4e184999-041e-4c11-9e86-faad487f2bad)
+  )
+  (text "MCU + DIGITAL\nRP2350A (QFN-60) - mind E9 erratum: external pulldowns on read inputs.\nW25Q128JV 16MB QSPI flash (wear-leveled).\n12MHz crystal. SWD 2x5 + labeled test points.\nI2S BCK/LRCK/DOUT + low-jitter 24.576MHz MCLK stay ON-CORE."
+    (at 110 45 0)
+    (effects (font (size 1.6 1.6)) (justify left top))
+    (uuid 43233868-23ee-43fa-b873-a47bffeacf5f)
+  )
+  (text "CLICK SOURCE\nPCM5102A I2S DAC (Burr-Brown).\nFed by dedicated low-jitter audio XO (ASEM1-24.576MHz),\nnot PIO-jittered MCLK."
+    (at 200 45 0)
+    (effects (font (size 1.6 1.6)) (justify left top))
+    (uuid a62ad51b-a1a9-4c34-b3d7-314c107afc7a)
+  )
+  (text "ANALOG INPUT (switchable line / instrument)\nProtection (non-negotiable): series DC-block film cap (blocks +48V phantom),\nclamp diodes/TVS to rails, series current-limit R.\nLINE: THAT1240 balanced receiver (laser-trimmed CMRR).\nINST: OPA1641 JFET Hi-Z buffer (>=1Mohm) + ~+10..15dB gain.\nK1 gold relay selects path (GPIO; touchscreen or optional face switch)."
+    (at 20 80 0)
+    (effects (font (size 1.6 1.6)) (justify left top))
+    (uuid 737ed14f-66db-4799-a337-21438143ce09)
+  )
+  (text "MIX + OUTPUT\nMix = digital/firmware (click level via DAC); analog stage at unity.\nTHAT1646 balanced driver + 47ohm build-out per leg.\nOutput level: Bourns 3296W 25-turn trim -> DAC FS = +4dBu (~+24dBu headroom).\nMUTE relay K2: fail-safe (de-energized = muted); HW supervisor, not MCU-dependent.\nGROUND-LIFT: face panel switch IN SERIES with core relay K3; soft-lift 100ohm||10nF.\nNO electrolytics in signal path - WIMA film caps, 0.1% thin-film R."
+    (at 110 80 0)
+    (effects (font (size 1.6 1.6)) (justify left top))
+    (uuid 99fe482f-1fde-4dd1-9579-56113dcb21bc)
+  )
+  (text "INDICATORS / MIDI / SPEAKER\nSIG/CLIP: peak detect -> LM393 -> RP2350 GPIO (UI) + LED lines on interconnect.\nMIDI: USB-MIDI default (firmware). DNP hardware option: H11L1 opto IN + 74LVC14 OUT/THRU.\nSpeaker: PAM8302 class-D, DNP per form factor.\nESD/EMI: USBLC6-2 on USB + CM choke; series R + ESD arrays on interconnect; ferrites at analog crossing."
+    (at 20 120 0)
+    (effects (font (size 1.6 1.6)) (justify left top))
+    (uuid 03eeefa8-7728-4e14-90c0-6d0496a0d207)
+  )
+  (text "INTERCONNECTS (see DESIGN.md s7)\nJ2 DIGITAL RIBBON 2x13 - Pico-pinout-compatible (SPI/I2C/ADC/buttons/LED + GNDLIFT_SW/LINEINST_SW/SIG_LED/CLIP_LED).\nJ3 ANALOG 2x5 - AOUT H/C, AIN H/C, AGND, CHASSIS/SHIELD, SPK+/- (DNP). Kept away from the fast digital ribbon.\nJ4 MIDI 1x6 - OUT A/B, IN A/B, +5V, GND (only if DNP MIDI populated).\nRelays + I2S + MCLK are core-only and NOT on the ribbon; a Pico test brain drives digital I/O but not the analog chain."
+    (at 110 120 0)
+    (effects (font (size 1.5 1.5)) (justify left top))
+    (uuid 0b1d2c3e-4f5a-6b7c-8d9e-0a1b2c3d4e5f)
+  )
+  (sheet_instances
+    (path "/" (page "1"))
+  )
+)

hardware/kicad/skidl.log

@@ -0,0 +1,9 @@
+WARNING: KICAD8_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: KICAD6_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: KICAD9_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: KICAD_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: KICAD7_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.

hardware/kicad/skidl_REPL.log

@@ -0,0 +1,9 @@
+WARNING: KICAD8_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: KICAD6_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: KICAD9_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: KICAD_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: KICAD7_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.

hardware/kicad/stage1_input.erc

@@ -0,0 +1,5 @@
+ERC WARNING: Only one pin (PASSIVE pin 1/~ of C/C1) attached to net AIN_HOT.
+ERC WARNING: Only one pin (PASSIVE pin 1/~ of C/C2) attached to net AIN_COLD.
+ERC INFO: 2 warnings found while running ERC.
+ERC INFO: 0 errors found while running ERC.
+

hardware/kicad/stage1_input.log

@@ -0,0 +1,37 @@
+WARNING: KICAD8_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: KICAD6_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: KICAD7_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: Missing tag on THAT1240 instantiated at /work/hardware/eda/circuits/stage1_input.py:47.
+WARNING: Random tag QgKieWmNoe generated for THAT1240.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage1_input.py:55.
+WARNING: Random tag iOc5_iqozn generated for C.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/stage1_input.py:56.
+WARNING: Random tag pZqcRwtR8R generated for R.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/stage1_input.py:56.
+WARNING: Random tag YRKF1YkzBd generated for R.
+WARNING: Missing tag on D instantiated at /work/hardware/eda/circuits/stage1_input.py:57.
+WARNING: Random tag 9_z9ZD6kzY generated for D.
+WARNING: Missing tag on D instantiated at /work/hardware/eda/circuits/stage1_input.py:57.
+WARNING: Random tag BmXsrS9O5J generated for D.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage1_input.py:55.
+WARNING: Random tag AA57mtziiu generated for C.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/stage1_input.py:56.
+WARNING: Random tag OlgSnmTOjl generated for R.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/stage1_input.py:56.
+WARNING: Random tag cs8OUXPRRM generated for R.
+WARNING: Missing tag on D instantiated at /work/hardware/eda/circuits/stage1_input.py:57.
+WARNING: Random tag i9mJhNwc3K generated for D.
+WARNING: Missing tag on D instantiated at /work/hardware/eda/circuits/stage1_input.py:57.
+WARNING: Random tag UUQtRJt6zT generated for D.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage1_input.py:76.
+WARNING: Random tag MU_6d6hLHv generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage1_input.py:76.
+WARNING: Random tag jSRPH3NSVb generated for C.
+WARNING: Missing tag on  instantiated at /work/hardware/kicad/<frozen importlib._bootstrap>:488.
+INFO: 31 warnings found while generating netlist.
+INFO: 0 errors found while generating netlist.
+

hardware/kicad/stage1_input_sklib.py

@@ -0,0 +1,26 @@
+from collections import defaultdict
+from skidl import Pin, Part, Alias, SchLib, SKIDL, TEMPLATE
+
+from skidl.pin import pin_types
+
+SKIDL_lib_version = '0.0.1'
+
+stage1_input = SchLib(tool=SKIDL).add_parts(*[
+        Part(**{ 'name':'THAT1240', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'THAT1240'}), 'ref_prefix':'U', 'fplist':None, 'footprint':'Package_SO:SOIC-8_3.9x4.9mm_P1.27mm', 'keywords':None, 'description':'', 'datasheet':None, 'pins':[
+            Pin(num='1',name='REF',func=pin_types.INPUT),
+            Pin(num='2',name='IN-',func=pin_types.INPUT),
+            Pin(num='3',name='IN+',func=pin_types.INPUT),
+            Pin(num='4',name='V-',func=pin_types.PWRIN),
+            Pin(num='5',name='SENSE',func=pin_types.PASSIVE),
+            Pin(num='6',name='OUT',func=pin_types.OUTPUT),
+            Pin(num='7',name='V+',func=pin_types.PWRIN),
+            Pin(num='8',name='NC',func=pin_types.NOCONNECT)] }),
+        Part(**{ 'name':'C', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'C'}), 'ref_prefix':'C', 'fplist':[''], 'footprint':'Capacitor_SMD:C_1206_3216Metric', 'keywords':'cap capacitor', 'description':'Unpolarized capacitor', 'datasheet':'~', 'pins':[
+            Pin(num='1',name='~',func=pin_types.PASSIVE,unit=1),
+            Pin(num='2',name='~',func=pin_types.PASSIVE,unit=1)], 'unit_defs':[] }),
+        Part(**{ 'name':'R', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'R'}), 'ref_prefix':'R', 'fplist':[''], 'footprint':'Resistor_SMD:R_0805_2012Metric', 'keywords':'R res resistor', 'description':'Resistor', 'datasheet':'~', 'pins':[
+            Pin(num='1',name='~',func=pin_types.PASSIVE,unit=1),
+            Pin(num='2',name='~',func=pin_types.PASSIVE,unit=1)], 'unit_defs':[] }),
+        Part(**{ 'name':'D', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'D'}), 'ref_prefix':'D', 'fplist':[''], 'footprint':'Diode_SMD:D_SOD-323', 'keywords':'diode', 'description':'Diode', 'datasheet':'~', 'pins':[
+            Pin(num='1',name='K',func=pin_types.PASSIVE,unit=1),
+            Pin(num='2',name='A',func=pin_types.PASSIVE,unit=1)], 'unit_defs':[] })])

hardware/kicad/stage1b_select.erc

@@ -0,0 +1,11 @@
+ERC WARNING: Only one pin (PASSIVE pin 10/COIL_B of TQ2SA-5V/K1) attached to net K1_DRV.
+ERC WARNING: Only one pin (PASSIVE pin 3/P1_COM of TQ2SA-5V/K1) attached to net AIN_HOT.
+ERC WARNING: Only one pin (PASSIVE pin 1/COIL_A of TQ2SA-5V/K1) attached to net +5V.
+ERC WARNING: Only one pin (PASSIVE pin 4/P1_NC of TQ2SA-5V/K1) attached to net RX_HOT_IN.
+ERC WARNING: Only one pin (PASSIVE pin 7/P2_NC of TQ2SA-5V/K1) attached to net RX_OUT.
+ERC WARNING: No pins attached to net SEL_LINST.
+ERC WARNING: No drivers for net SEL_LINST.
+ERC WARNING: Only one pin (PASSIVE pin 8/P2_COM of TQ2SA-5V/K1) attached to net STAGE1_OUT.
+ERC INFO: 8 warnings found while running ERC.
+ERC INFO: 0 errors found while running ERC.
+

hardware/kicad/stage1b_select.log

@@ -0,0 +1,31 @@
+WARNING: KICAD8_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: KICAD6_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: KICAD7_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: Missing tag on OPA1641 instantiated at /work/hardware/eda/circuits/stage1b_select.py:55.
+WARNING: Random tag JMxNatPRjd generated for OPA1641.
+WARNING: Missing tag on TQ2SA-5V instantiated at /work/hardware/eda/circuits/stage1b_select.py:72.
+WARNING: Random tag CfzYAxfHjh generated for TQ2SA-5V.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage1b_select.py:97.
+WARNING: Random tag Sd0rgwy5pV generated for C.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/stage1b_select.py:98.
+WARNING: Random tag OoRZG4Rm3b generated for R.
+WARNING: Missing tag on D instantiated at /work/hardware/eda/circuits/stage1b_select.py:99.
+WARNING: Random tag RSLeGReAd9 generated for D.
+WARNING: Missing tag on D instantiated at /work/hardware/eda/circuits/stage1b_select.py:99.
+WARNING: Random tag UOfVnOhhVN generated for D.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/stage1b_select.py:108.
+WARNING: Random tag 3vZeT_Vysx generated for R.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/stage1b_select.py:108.
+WARNING: Random tag u1DrTpQXsB generated for R.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage1b_select.py:116.
+WARNING: Random tag UbVM1UVNF7 generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage1b_select.py:116.
+WARNING: Random tag 073687vTIh generated for C.
+WARNING: Missing tag on  instantiated at /work/hardware/kicad/<frozen importlib._bootstrap>:488.
+INFO: 25 warnings found while generating netlist.
+INFO: 0 errors found while generating netlist.
+

hardware/kicad/stage1b_select_sklib.py

@@ -0,0 +1,37 @@
+from collections import defaultdict
+from skidl import Pin, Part, Alias, SchLib, SKIDL, TEMPLATE
+
+from skidl.pin import pin_types
+
+SKIDL_lib_version = '0.0.1'
+
+stage1b_select = SchLib(tool=SKIDL).add_parts(*[
+        Part(**{ 'name':'OPA1641', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'OPA1641'}), 'ref_prefix':'U', 'fplist':None, 'footprint':'Package_SO:SOIC-8_3.9x4.9mm_P1.27mm', 'keywords':None, 'description':'', 'datasheet':None, 'pins':[
+            Pin(num='1',name='NC1',func=pin_types.NOCONNECT),
+            Pin(num='2',name='-IN',func=pin_types.INPUT),
+            Pin(num='3',name='+IN',func=pin_types.INPUT),
+            Pin(num='4',name='V-',func=pin_types.PWRIN),
+            Pin(num='5',name='NC5',func=pin_types.NOCONNECT),
+            Pin(num='6',name='OUT',func=pin_types.OUTPUT),
+            Pin(num='7',name='V+',func=pin_types.PWRIN),
+            Pin(num='8',name='NC8',func=pin_types.NOCONNECT)] }),
+        Part(**{ 'name':'TQ2SA-5V', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'TQ2SA-5V'}), 'ref_prefix':'K', 'fplist':None, 'footprint':'Relay_SMD:Relay_DPDT_Panasonic_TQ2-SA', 'keywords':None, 'description':'', 'datasheet':None, 'pins':[
+            Pin(num='1',name='COIL_A',func=pin_types.PASSIVE),
+            Pin(num='10',name='COIL_B',func=pin_types.PASSIVE),
+            Pin(num='3',name='P1_COM',func=pin_types.PASSIVE),
+            Pin(num='4',name='P1_NC',func=pin_types.PASSIVE),
+            Pin(num='2',name='P1_NO',func=pin_types.PASSIVE),
+            Pin(num='8',name='P2_COM',func=pin_types.PASSIVE),
+            Pin(num='7',name='P2_NC',func=pin_types.PASSIVE),
+            Pin(num='9',name='P2_NO',func=pin_types.PASSIVE),
+            Pin(num='5',name='NC5',func=pin_types.NOCONNECT),
+            Pin(num='6',name='NC6',func=pin_types.NOCONNECT)] }),
+        Part(**{ 'name':'C', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'C'}), 'ref_prefix':'C', 'fplist':[''], 'footprint':'Capacitor_SMD:C_1206_3216Metric', 'keywords':'cap capacitor', 'description':'Unpolarized capacitor', 'datasheet':'~', 'pins':[
+            Pin(num='1',name='~',func=pin_types.PASSIVE,unit=1),
+            Pin(num='2',name='~',func=pin_types.PASSIVE,unit=1)], 'unit_defs':[] }),
+        Part(**{ 'name':'R', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'R'}), 'ref_prefix':'R', 'fplist':[''], 'footprint':'Resistor_SMD:R_0805_2012Metric', 'keywords':'R res resistor', 'description':'Resistor', 'datasheet':'~', 'pins':[
+            Pin(num='1',name='~',func=pin_types.PASSIVE,unit=1),
+            Pin(num='2',name='~',func=pin_types.PASSIVE,unit=1)], 'unit_defs':[] }),
+        Part(**{ 'name':'D', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'D'}), 'ref_prefix':'D', 'fplist':[''], 'footprint':'Diode_SMD:D_SOD-323', 'keywords':'diode', 'description':'Diode', 'datasheet':'~', 'pins':[
+            Pin(num='1',name='K',func=pin_types.PASSIVE,unit=1),
+            Pin(num='2',name='A',func=pin_types.PASSIVE,unit=1)], 'unit_defs':[] })])

hardware/kicad/stage2_dac.erc

@@ -0,0 +1,15 @@
+ERC WARNING: Only one pin (INPUT pin 15/LRCK of PCM5102A/U3) attached to net I2S_LRCK.
+ERC WARNING: No drivers for net I2S_LRCK.
+ERC WARNING: Insufficient drive current on net I2S_LRCK for pin INPUT pin 15/LRCK of PCM5102A/U3.
+ERC WARNING: Only one pin (INPUT pin 13/BCK of PCM5102A/U3) attached to net I2S_BCK.
+ERC WARNING: No drivers for net I2S_BCK.
+ERC WARNING: Insufficient drive current on net I2S_BCK for pin INPUT pin 13/BCK of PCM5102A/U3.
+ERC WARNING: Only one pin (INPUT pin 12/SCK of PCM5102A/U3) attached to net MCLK.
+ERC WARNING: No drivers for net MCLK.
+ERC WARNING: Insufficient drive current on net MCLK for pin INPUT pin 12/SCK of PCM5102A/U3.
+ERC WARNING: Only one pin (INPUT pin 14/DIN of PCM5102A/U3) attached to net I2S_DIN.
+ERC WARNING: No drivers for net I2S_DIN.
+ERC WARNING: Insufficient drive current on net I2S_DIN for pin INPUT pin 14/DIN of PCM5102A/U3.
+ERC INFO: 12 warnings found while running ERC.
+ERC INFO: 0 errors found while running ERC.
+

hardware/kicad/stage2_dac.log

@@ -0,0 +1,45 @@
+WARNING: KICAD8_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: KICAD6_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: KICAD7_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: Missing tag on PCM5102A instantiated at /work/hardware/eda/circuits/stage2_dac.py:65.
+WARNING: Random tag SnNljvRqpw generated for PCM5102A.
+WARNING: Missing tag on OPA1612 instantiated at /work/hardware/eda/circuits/stage2_dac.py:80.
+WARNING: Random tag xlt7MeMuUW generated for OPA1612.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage2_dac.py:90.
+WARNING: Random tag APxc1ZswyC generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage2_dac.py:90.
+WARNING: Random tag 2Lpho8vvNO generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage2_dac.py:90.
+WARNING: Random tag ckOnqrtEN_ generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage2_dac.py:91.
+WARNING: Random tag u0XfWM3NJZ generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage2_dac.py:95.
+WARNING: Random tag 0nDWAElKnx generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage2_dac.py:97.
+WARNING: Random tag enBI6FilVb generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage2_dac.py:98.
+WARNING: Random tag BsHVUTUgsl generated for C.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/stage2_dac.py:106.
+WARNING: Random tag MwfOtBOy0H generated for R.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/stage2_dac.py:115.
+WARNING: Random tag T191zb3J0X generated for R.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/stage2_dac.py:118.
+WARNING: Random tag PbFpsp3Kl4 generated for R.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/stage2_dac.py:118.
+WARNING: Random tag uQ27wvkIQL generated for R.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage2_dac.py:119.
+WARNING: Random tag xSn6HarfSW generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage2_dac.py:119.
+WARNING: Random tag mU_gTQB1ji generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage2_dac.py:131.
+WARNING: Random tag u20v3iP1Ti generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage2_dac.py:131.
+WARNING: Random tag ZBz2Y2o1hX generated for C.
+WARNING: Missing tag on  instantiated at /work/hardware/kicad/<frozen importlib._bootstrap>:488.
+INFO: 39 warnings found while generating netlist.
+INFO: 0 errors found while generating netlist.
+

hardware/kicad/stage2_dac_sklib.py

@@ -0,0 +1,44 @@
+from collections import defaultdict
+from skidl import Pin, Part, Alias, SchLib, SKIDL, TEMPLATE
+
+from skidl.pin import pin_types
+
+SKIDL_lib_version = '0.0.1'
+
+stage2_dac = SchLib(tool=SKIDL).add_parts(*[
+        Part(**{ 'name':'PCM5102A', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'PCM5102A'}), 'ref_prefix':'U', 'fplist':None, 'footprint':'Package_SO:TSSOP-20_4.4x6.5mm_P0.65mm', 'keywords':None, 'description':'', 'datasheet':None, 'pins':[
+            Pin(num='1',name='CPVDD',func=pin_types.PWRIN),
+            Pin(num='2',name='CAPP',func=pin_types.PASSIVE),
+            Pin(num='3',name='CPGND',func=pin_types.PWRIN),
+            Pin(num='4',name='CAPM',func=pin_types.PASSIVE),
+            Pin(num='5',name='VNEG',func=pin_types.PASSIVE),
+            Pin(num='6',name='OUTL',func=pin_types.OUTPUT),
+            Pin(num='7',name='OUTR',func=pin_types.OUTPUT),
+            Pin(num='8',name='AVDD',func=pin_types.PWRIN),
+            Pin(num='9',name='AGND',func=pin_types.PWRIN),
+            Pin(num='10',name='DEMP',func=pin_types.INPUT),
+            Pin(num='11',name='FLT',func=pin_types.INPUT),
+            Pin(num='12',name='SCK',func=pin_types.INPUT),
+            Pin(num='13',name='BCK',func=pin_types.INPUT),
+            Pin(num='14',name='DIN',func=pin_types.INPUT),
+            Pin(num='15',name='LRCK',func=pin_types.INPUT),
+            Pin(num='16',name='FMT',func=pin_types.INPUT),
+            Pin(num='17',name='XSMT',func=pin_types.INPUT),
+            Pin(num='18',name='LDOO',func=pin_types.PWROUT),
+            Pin(num='19',name='DGND',func=pin_types.PWRIN),
+            Pin(num='20',name='DVDD',func=pin_types.PWRIN)] }),
+        Part(**{ 'name':'OPA1612', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'OPA1612'}), 'ref_prefix':'U', 'fplist':None, 'footprint':'Package_SO:SOIC-8_3.9x4.9mm_P1.27mm', 'keywords':None, 'description':'', 'datasheet':None, 'pins':[
+            Pin(num='1',name='OUTA',func=pin_types.OUTPUT),
+            Pin(num='2',name='-INA',func=pin_types.INPUT),
+            Pin(num='3',name='+INA',func=pin_types.INPUT),
+            Pin(num='4',name='V-',func=pin_types.PWRIN),
+            Pin(num='5',name='+INB',func=pin_types.INPUT),
+            Pin(num='6',name='-INB',func=pin_types.INPUT),
+            Pin(num='7',name='OUTB',func=pin_types.OUTPUT),
+            Pin(num='8',name='V+',func=pin_types.PWRIN)] }),
+        Part(**{ 'name':'C', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'C'}), 'ref_prefix':'C', 'fplist':[''], 'footprint':'Capacitor_SMD:C_0805_2012Metric', 'keywords':'cap capacitor', 'description':'Unpolarized capacitor', 'datasheet':'~', 'pins':[
+            Pin(num='1',name='~',func=pin_types.PASSIVE,unit=1),
+            Pin(num='2',name='~',func=pin_types.PASSIVE,unit=1)], 'unit_defs':[] }),
+        Part(**{ 'name':'R', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'R'}), 'ref_prefix':'R', 'fplist':[''], 'footprint':'Resistor_SMD:R_0805_2012Metric', 'keywords':'R res resistor', 'description':'Resistor', 'datasheet':'~', 'pins':[
+            Pin(num='1',name='~',func=pin_types.PASSIVE,unit=1),
+            Pin(num='2',name='~',func=pin_types.PASSIVE,unit=1)], 'unit_defs':[] })])

hardware/kicad/stage3_sum.erc

@@ -0,0 +1,5 @@
+ERC WARNING: Only one pin (PASSIVE pin 1/~ of R/R1) attached to net STAGE1_OUT.
+ERC WARNING: Only one pin (PASSIVE pin 1/~ of R/R2) attached to net CLICK_OUT.
+ERC INFO: 2 warnings found while running ERC.
+ERC INFO: 0 errors found while running ERC.
+

hardware/kicad/stage3_sum.log

@@ -0,0 +1,23 @@
+WARNING: KICAD8_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: KICAD6_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: KICAD7_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: Missing tag on OPA1612 instantiated at /work/hardware/eda/circuits/stage3_sum.py:50.
+WARNING: Random tag 5n2wh6xRRe generated for OPA1612.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/stage3_sum.py:53.
+WARNING: Random tag PsTgUzSm6S generated for R.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/stage3_sum.py:53.
+WARNING: Random tag MJ5MDnj_yt generated for R.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/stage3_sum.py:53.
+WARNING: Random tag RyhIEBAL2O generated for R.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage3_sum.py:63.
+WARNING: Random tag oOB0ftP80i generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage3_sum.py:63.
+WARNING: Random tag NmK6U68Pr1 generated for C.
+WARNING: Missing tag on  instantiated at /work/hardware/kicad/<frozen importlib._bootstrap>:488.
+INFO: 17 warnings found while generating netlist.
+INFO: 0 errors found while generating netlist.
+

hardware/kicad/stage3_sum_sklib.py

@@ -0,0 +1,23 @@
+from collections import defaultdict
+from skidl import Pin, Part, Alias, SchLib, SKIDL, TEMPLATE
+
+from skidl.pin import pin_types
+
+SKIDL_lib_version = '0.0.1'
+
+stage3_sum = SchLib(tool=SKIDL).add_parts(*[
+        Part(**{ 'name':'OPA1612', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'OPA1612'}), 'ref_prefix':'U', 'fplist':None, 'footprint':'Package_SO:SOIC-8_3.9x4.9mm_P1.27mm', 'keywords':None, 'description':'', 'datasheet':None, 'pins':[
+            Pin(num='1',name='OUTA',func=pin_types.OUTPUT),
+            Pin(num='2',name='-INA',func=pin_types.INPUT),
+            Pin(num='3',name='+INA',func=pin_types.INPUT),
+            Pin(num='4',name='V-',func=pin_types.PWRIN),
+            Pin(num='5',name='+INB',func=pin_types.INPUT),
+            Pin(num='6',name='-INB',func=pin_types.INPUT),
+            Pin(num='7',name='OUTB',func=pin_types.OUTPUT),
+            Pin(num='8',name='V+',func=pin_types.PWRIN)] }),
+        Part(**{ 'name':'R', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'R'}), 'ref_prefix':'R', 'fplist':[''], 'footprint':'Resistor_SMD:R_0805_2012Metric', 'keywords':'R res resistor', 'description':'Resistor', 'datasheet':'~', 'pins':[
+            Pin(num='1',name='~',func=pin_types.PASSIVE,unit=1),
+            Pin(num='2',name='~',func=pin_types.PASSIVE,unit=1)], 'unit_defs':[] }),
+        Part(**{ 'name':'C', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'C'}), 'ref_prefix':'C', 'fplist':[''], 'footprint':'Capacitor_SMD:C_0805_2012Metric', 'keywords':'cap capacitor', 'description':'Unpolarized capacitor', 'datasheet':'~', 'pins':[
+            Pin(num='1',name='~',func=pin_types.PASSIVE,unit=1),
+            Pin(num='2',name='~',func=pin_types.PASSIVE,unit=1)], 'unit_defs':[] })])

hardware/kicad/stage4_driver.erc

@@ -0,0 +1,12 @@
+ERC WARNING: Only one pin (PASSIVE pin 10/COIL_B of TQ2SA-5V/K2) attached to net K2_DRV.
+ERC WARNING: Only one pin (PASSIVE pin 1/1 of R_Potentiometer/RV1) attached to net MIX_OUT.
+ERC WARNING: Only one pin (PASSIVE pin 10/COIL_B of TQ2SA-5V/K3) attached to net K3_DRV.
+ERC WARNING: Unconnected pin: PASSIVE pin 2/P1_NO of TQ2SA-5V/K2.
+ERC WARNING: Unconnected pin: PASSIVE pin 9/P2_NO of TQ2SA-5V/K2.
+ERC WARNING: Unconnected pin: PASSIVE pin 2/P1_NO of TQ2SA-5V/K3.
+ERC WARNING: Unconnected pin: PASSIVE pin 8/P2_COM of TQ2SA-5V/K3.
+ERC WARNING: Unconnected pin: PASSIVE pin 7/P2_NC of TQ2SA-5V/K3.
+ERC WARNING: Unconnected pin: PASSIVE pin 9/P2_NO of TQ2SA-5V/K3.
+ERC INFO: 9 warnings found while running ERC.
+ERC INFO: 0 errors found while running ERC.
+

hardware/kicad/stage4_driver.log

@@ -0,0 +1,31 @@
+WARNING: KICAD8_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: KICAD6_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: KICAD7_SYMBOL_DIR environment variable is missing, so the default KiCad symbol libraries won't be searched. @ [/work/hardware/kicad/<frozen importlib._bootstrap_external>:995=>/work/hardware/kicad/<frozen importlib._bootstrap>:488]
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: fp-lib-table file was not found. Component footprints are not available.
+WARNING: Missing tag on THAT1646 instantiated at /work/hardware/eda/circuits/stage4_driver.py:57.
+WARNING: Random tag jOycpJtysP generated for THAT1646.
+WARNING: Missing tag on TQ2SA-5V instantiated at /work/hardware/eda/circuits/stage4_driver.py:75.
+WARNING: Random tag 8YvHjEQvvL generated for TQ2SA-5V.
+WARNING: Missing tag on TQ2SA-5V instantiated at /work/hardware/eda/circuits/stage4_driver.py:75.
+WARNING: Random tag gbZbaJRgHN generated for TQ2SA-5V.
+WARNING: Missing tag on R_Potentiometer instantiated at /work/hardware/eda/circuits/stage4_driver.py:82.
+WARNING: Random tag TtWL0siwIj generated for R_Potentiometer.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage4_driver.py:91.
+WARNING: Random tag Il2xsDxaas generated for C.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage4_driver.py:91.
+WARNING: Random tag h4JnvQCBxp generated for C.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/stage4_driver.py:94.
+WARNING: Random tag 49MKQ_ERoo generated for R.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/stage4_driver.py:94.
+WARNING: Random tag L4esGcufU5 generated for R.
+WARNING: Missing tag on R instantiated at /work/hardware/eda/circuits/stage4_driver.py:105.
+WARNING: Random tag xtw8oitG50 generated for R.
+WARNING: Missing tag on C instantiated at /work/hardware/eda/circuits/stage4_driver.py:105.
+WARNING: Random tag 5KGv1Z40Bi generated for C.
+WARNING: Missing tag on  instantiated at /work/hardware/kicad/<frozen importlib._bootstrap>:488.
+INFO: 25 warnings found while generating netlist.
+INFO: 0 errors found while generating netlist.
+

hardware/kicad/stage4_driver_sklib.py

@@ -0,0 +1,38 @@
+from collections import defaultdict
+from skidl import Pin, Part, Alias, SchLib, SKIDL, TEMPLATE
+
+from skidl.pin import pin_types
+
+SKIDL_lib_version = '0.0.1'
+
+stage4_driver = SchLib(tool=SKIDL).add_parts(*[
+        Part(**{ 'name':'THAT1646', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'THAT1646'}), 'ref_prefix':'U', 'fplist':None, 'footprint':'Package_SO:SOIC-8_3.9x4.9mm_P1.27mm', 'keywords':None, 'description':'', 'datasheet':None, 'pins':[
+            Pin(num='1',name='OUT-',func=pin_types.OUTPUT),
+            Pin(num='2',name='SNS-',func=pin_types.INPUT),
+            Pin(num='3',name='GND',func=pin_types.PWRIN),
+            Pin(num='4',name='IN',func=pin_types.INPUT),
+            Pin(num='5',name='V-',func=pin_types.PWRIN),
+            Pin(num='6',name='V+',func=pin_types.PWRIN),
+            Pin(num='7',name='SNS+',func=pin_types.INPUT),
+            Pin(num='8',name='OUT+',func=pin_types.OUTPUT)] }),
+        Part(**{ 'name':'TQ2SA-5V', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'TQ2SA-5V'}), 'ref_prefix':'K', 'fplist':None, 'footprint':'Relay_SMD:Relay_DPDT_Panasonic_TQ2-SA', 'keywords':None, 'description':'', 'datasheet':None, 'pins':[
+            Pin(num='1',name='COIL_A',func=pin_types.PASSIVE),
+            Pin(num='10',name='COIL_B',func=pin_types.PASSIVE),
+            Pin(num='3',name='P1_COM',func=pin_types.PASSIVE),
+            Pin(num='4',name='P1_NC',func=pin_types.PASSIVE),
+            Pin(num='2',name='P1_NO',func=pin_types.PASSIVE),
+            Pin(num='8',name='P2_COM',func=pin_types.PASSIVE),
+            Pin(num='7',name='P2_NC',func=pin_types.PASSIVE),
+            Pin(num='9',name='P2_NO',func=pin_types.PASSIVE),
+            Pin(num='5',name='NC5',func=pin_types.NOCONNECT),
+            Pin(num='6',name='NC6',func=pin_types.NOCONNECT)] }),
+        Part(**{ 'name':'R_Potentiometer', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'R_Potentiometer'}), 'ref_prefix':'RV', 'fplist':[''], 'footprint':'Potentiometer_THT:Potentiometer_Bourns_3296W_Vertical', 'keywords':'resistor variable', 'description':'Potentiometer', 'datasheet':'~', 'pins':[
+            Pin(num='1',name='1',func=pin_types.PASSIVE,unit=1),
+            Pin(num='3',name='3',func=pin_types.PASSIVE,unit=1),
+            Pin(num='2',name='2',func=pin_types.PASSIVE,unit=1)], 'unit_defs':[] }),
+        Part(**{ 'name':'C', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'C'}), 'ref_prefix':'C', 'fplist':[''], 'footprint':'Capacitor_SMD:C_0805_2012Metric', 'keywords':'cap capacitor', 'description':'Unpolarized capacitor', 'datasheet':'~', 'pins':[
+            Pin(num='1',name='~',func=pin_types.PASSIVE,unit=1),
+            Pin(num='2',name='~',func=pin_types.PASSIVE,unit=1)], 'unit_defs':[] }),
+        Part(**{ 'name':'R', 'dest':TEMPLATE, 'tool':SKIDL, 'aliases':Alias({'R'}), 'ref_prefix':'R', 'fplist':[''], 'footprint':'Resistor_SMD:R_0805_2012Metric', 'keywords':'R res resistor', 'description':'Resistor', 'datasheet':'~', 'pins':[
+            Pin(num='1',name='~',func=pin_types.PASSIVE,unit=1),
+            Pin(num='2',name='~',func=pin_types.PASSIVE,unit=1)], 'unit_defs':[] })])

info-explorer.html

@@ -0,0 +1,169 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+<meta charset="UTF-8" />
+<meta name="viewport" content="width=device-width, initial-scale=1.0" />
+<title>VARASYS PM_X-1 Explorer - wiring, parts &amp; firmware (Pimoroni Explorer / RP2350)</title>
+<meta name="description" content="PM_X-1 Explorer - the Pimoroni Explorer (PIM744, RP2350) as a 6-button polymeter metronome with live-sync to the web editor. Pinout, parts list, and the precompiled CircuitPython firmware bundle." />
+<link rel="icon" type="image/svg+xml" href="data:image/svg+xml;base64,@BUILD:favicon@">
+<script>
+  (function(){ try{ var p = localStorage.getItem("metronome.theme");
+    if (p!=="light" && p!=="dark" && p!=="system") p = "system";
+    document.documentElement.dataset.theme = p==="system" ? (matchMedia("(prefers-color-scheme: light)").matches ? "light" : "dark") : p;
+  } catch(e){ document.documentElement.dataset.theme = "dark"; } })();
+</script>
+<style>
+  /*@BUILD:include:src/base.css@*/
+  :root{ --bg1:#12151c; --bg2:#05070a; --txt:#c7d0db; --muted:#7f8b9a; --link:#6cb6ff;
+    --panel-bg:#161b22; --panel-bd:#2a313c; --field-bg:#0e1116; --field-bd:#2a313c; --silk:#aab2bc; }
+  :root[data-theme="light"]{ --bg1:#f5f8fc; --bg2:#dde4ec; --txt:#1e2630; --muted:#5c6776; --link:#1769c4;
+    --panel-bg:#ffffff; --panel-bd:#d2dae4; --field-bg:#f1f4f8; --field-bd:#d2dae4; }
+  body{ margin:0; min-height:100vh; padding:22px 16px 56px; color:var(--txt);
+    background:radial-gradient(circle at 50% -8%, var(--bg1), var(--bg2)); }
+  a{ color:var(--link); }
+  main{ width:100%; max-width:980px; margin:0 auto; }
+  .info-hero{ text-align:center; padding:16px 8px 2px; }
+  .info-hero h1{ font-size:clamp(24px,5vw,36px); margin:0; letter-spacing:-.01em; }
+  .info-hero .sub{ margin:9px auto 0; max-width:64ch; font-size:14.5px; }
+  .steps{ width:100%; max-width:760px; margin:8px auto 0; color:var(--muted); font-size:14px; line-height:1.6; }
+  .steps li{ margin:5px 0; }
+  .steps code, .about code, .sub code { background:var(--field-bg); border:1px solid var(--field-bd); border-radius:5px; padding:1px 5px; font-size:12.5px; }
+  .dl{ display:inline-flex; align-items:center; gap:7px; margin:4px 10px 4px 0; padding:9px 14px; border-radius:10px;
+    background:linear-gradient(180deg,#34c6ff,var(--cyan)); color:#04121b; font-weight:700; text-decoration:none; font-size:13.5px; }
+  .dl.alt{ background:var(--field-bg); color:var(--txt); border:1px solid var(--field-bd); font-weight:600; }
+</style>
+</head>
+<body>
+
+/*@BUILD:include:src/header.html@*/
+
+<main>
+  <section class="info-hero">
+    <h1>PM_X-1 Explorer</h1>
+    <p class="sub">The off-the-shelf <b>Pimoroni Explorer Kit</b> (RP2350, 2.8&quot; LCD, 6 buttons, piezo) as a polymeter metronome - sibling to the PM_K-1 Kit, sharing the engine, program-string grammar, and live-sync protocol with the web editor.</p>
+  </section>
+
+<section class="about">
+  <h2>What it is</h2>
+  <div class="ff-tags"><span class="hw">Buildable now</span><span>RP2350 (Pico 2 class)</span><span>Pimoroni Explorer PIM744</span><span>~$60</span></div>
+  <p>The <a href="https://shop.pimoroni.com/products/explorer" target="_blank" rel="noopener">Pimoroni Explorer Kit (PIM744)</a> is a finished
+    development board: <b>RP2350B</b> built in, <b>2.8&quot; ST7789V 320x240 IPS LCD</b>, <b>6 user buttons</b> (A/B/C
+    on the left of the screen, X/Y/Z on the right), a <b>piezo speaker</b>, USB-C, a JST-PH battery
+    connector, and a mini breadboard with 6 GPIOs / 3 ADCs broken out for sensor projects. No soldering;
+    you flash CircuitPython and drop the firmware on. <b>No touchscreen, no joystick, no RGB LED</b> -
+    everything is driven from the 6 buttons.</p>
+  <p>It runs the same <b>polymeter engine</b> and the same <b>program strings</b> as the web editor.
+    Beat editing is done in the browser; <b>Live sync</b> mirrors edits to the device in real time
+    (HELLO/FULL/DELTA over USB-MIDI), and the device mirrors play/stop/tempo/track changes back. The
+    piezo clicks; a tiny on-screen dot shows run state.</p>
+</section>
+
+<details class="spec" open>
+  <summary>Wiring - the Pimoroni Explorer fixed pinout (no breadboarding required)</summary>
+  <div class="spec-body">
+    <p class="sub">Everything is wired on the board; this is what the firmware reads. The display is driven by an 8-bit parallel bus initialised by CircuitPython's official board definition - we use <code>board.DISPLAY</code> directly.</p>
+    <table class="bom">
+      <thead><tr><th>Component</th><th>RP2350 pins</th></tr></thead>
+      <tbody>
+        <tr class="grp"><td colspan="2">Display - 2.8&quot; ST7789V, 320x240 (8-bit parallel 8080)</td></tr>
+        <tr><td class="part">BL / CS / DC / WR / RD / D0-D7</td><td>GP26 / GP27 / GP28 / GP30 / GP31 / GP32-GP39 (board.c)</td></tr>
+        <tr class="grp"><td colspan="2">Buttons (digital, pull-up)</td></tr>
+        <tr><td class="part">A (play/stop) / B (tap tempo) / C (menu)</td><td>GP16 / GP15 / GP14 (left side, top to bottom)</td></tr>
+        <tr><td class="part">X (prev track) / Y (-bpm) / Z (next track)</td><td>GP17 / GP18 / GP19 (right side, top to bottom)</td></tr>
+        <tr class="grp"><td colspan="2">Audio</td></tr>
+        <tr><td class="part">Piezo PWM</td><td>GP12</td></tr>
+        <tr><td class="part">Amp enable</td><td>GP13</td></tr>
+        <tr class="grp"><td colspan="2">I2C (QwSTEMMA - unused by the firmware, free for sensors)</td></tr>
+        <tr><td class="part">SDA / SCL</td><td>GP20 / GP21</td></tr>
+      </tbody>
+    </table>
+  </div>
+</details>
+
+<details class="spec" open>
+  <summary>Controls</summary>
+  <div class="spec-body">
+    <table class="bom">
+      <thead><tr><th>Button</th><th>Action</th></tr></thead>
+      <tbody>
+        <tr><td class="part">A</td><td>play / stop</td></tr>
+        <tr><td class="part">B</td><td>tap tempo</td></tr>
+        <tr><td class="part">C</td><td>menu (Settings / Practice log / Help / About)</td></tr>
+        <tr><td class="part">X</td><td>prev track (hold to repeat)</td></tr>
+        <tr><td class="part">Z</td><td>next track (hold to repeat)</td></tr>
+        <tr><td class="part">Y</td><td>tempo -1 (hold = -5 after 1.5 s)</td></tr>
+        <tr><td class="part">X + Z (chord)</td><td>tempo +1 (same hold rule as Y)</td></tr>
+        <tr class="grp"><td colspan="2">In a menu</td></tr>
+        <tr><td class="part">X / Z</td><td>move cursor up / down (Help: prev / next page)</td></tr>
+        <tr><td class="part">Y</td><td>decrement the focused value</td></tr>
+        <tr><td class="part">A</td><td>cycle / increment / select</td></tr>
+        <tr><td class="part">B</td><td>back (cancel)</td></tr>
+        <tr><td class="part">C</td><td>close the menu</td></tr>
+      </tbody>
+    </table>
+  </div>
+</details>
+
+<details class="spec" open>
+  <summary>Parts</summary>
+  <div class="spec-body">
+    <p class="sub">A finished development board, not a custom build - ballpark one-off price (USD).</p>
+    <table class="bom">
+      <thead><tr><th>Part</th><th class="q">Qty</th><th class="c">~$</th></tr></thead>
+      <tbody>
+        <tr><td class="part">Pimoroni Explorer Kit (PIM744) <span class="spec">- RP2350B, 2.8&quot; ST7789V, 6 buttons, piezo + amp, USB-C</span></td><td class="q">1</td><td class="c">60</td></tr>
+        <tr><td class="part">USB-C cable <span class="spec">- power + flashing</span></td><td class="q">1</td><td class="c">2</td></tr>
+        <tr class="total"><td>Total (one-off)</td><td class="q"></td><td class="c">&asymp; $62</td></tr>
+      </tbody>
+    </table>
+    <p class="sub" style="margin-top:10px">Reference: <a href="https://shop.pimoroni.com/products/explorer" target="_blank" rel="noopener">Pimoroni Explorer product page</a>
+      &middot; <a href="https://github.com/pimoroni/explorer" target="_blank" rel="noopener">vendor code</a>
+      &middot; <a href="https://circuitpython.org/board/pimoroni_explorer2350/" target="_blank" rel="noopener">CircuitPython for Pimoroni Explorer (RP2350)</a>.</p>
+  </div>
+</details>
+
+<details class="spec" open>
+  <summary>Firmware - self-contained appliance (USB drive &middot; web-driven editing via Live sync &middot; MIDI audio &middot; practice log)</summary>
+  <div class="spec-body">
+    <p class="sub">The firmware turns the Explorer into a self-contained appliance: it mounts as a
+      <b>USB drive</b> carrying the (precompiled) firmware, your tracks and an offline copy of this editor;
+      drives a lanes/pads display with <b>web-driven editing</b> via <b>Live sync</b>; <b>logs your practice</b> to
+      <code>history.json</code>; takes new set lists <b>pushed from the editor over USB-MIDI</b>; and plays
+      out your <b>computer's speakers over USB-MIDI</b>. By default the firmware owns the drive (read-only to
+      the computer - so it can log and can't be accidentally erased); hold <b>button A</b> at power-on for
+      editor mode (drive writable).</p>
+    <p>
+      <a class="dl" href="/pm_x1_circuitpy.zip" download>Download CircuitPython bundle &darr;</a>
+      <a class="dl alt" href="https://codeberg.org/VARASYS/metronome/src/branch/main/pico-explorer" target="_blank" rel="noopener">Source + README &nearr;</a>
+    </p>
+    <ol class="steps">
+      <li>Flash <b>CircuitPython for Pimoroni Explorer (RP2350)</b>
+        (<a href="https://circuitpython.org/board/pimoroni_explorer2350/" target="_blank" rel="noopener">download</a>)
+        via BOOTSEL, unzip the bundle onto <code>CIRCUITPY</code>, and power-cycle. It boots into appliance mode.</li>
+      <li><b>Edit on the web:</b> open the <a href="/editor-beta.html">editor (beta)</a> in Chrome / Edge / Firefox,
+        click <b>&#x1f517; Live sync</b>, and the Explorer mirrors your edits live (beats, tempo, track changes).</li>
+      <li><b>Save a set list to the device</b> for offline use: set-list <b>&middot;&middot;&middot;</b> menu &rarr;
+        <b>&#x1f4DF; Save to device</b>. It's pushed over USB-MIDI; the device persists it to
+        <code>/programs.json</code>.</li>
+      <li><b>Play through your computer:</b> click <b>&#x1f3b9; Device audio</b>, then press <b>A</b> on the device -
+        the full groove sounds through your speakers over USB-MIDI, in sync. A <b>MIDI</b> badge appears in the
+        header and the piezo auto-mutes.</li>
+      <li><b>Practice log:</b> press <b>C</b> &rarr; <b>Practice log</b>. Plays over 5 s appear (time &middot; BPM &middot; duration &middot; bars).</li>
+      <li><b>Firmware updates:</b> &middot;&middot;&middot; menu &rarr; <b>&#x2B06; Update firmware</b> - the editor reads
+        the device id (X = Explorer), fetches the matching <code>pico-explorer-app.mpy</code>, and pushes it
+        over USB-MIDI. The device A/B-updates with automatic rollback if a build won't boot.</li>
+    </ol>
+  </div>
+</details>
+
+<p class="sub" style="max-width:760px;margin:14px auto 0">Pairs with the touch-driven <a href="/info-kit.html">PM_K-1 Kit</a> - same engine, same programs.json, same web editor.</p>
+</main>
+
+/*@BUILD:include:src/footer.html@*/
+
+<script>
+const APP_VERSION = "v0.0.1-dev";
+/*@BUILD:include:src/chrome.js@*/
+</script>
+</body>
+</html>

pico-cp/app.py

@@ -18,7 +18,8 @@
 
 import board, busio, digitalio, analogio, pwmio, displayio, vectorio, time, json, gc, os, supervisor
 supervisor.runtime.autoreload = False   # we write our own files (log + pushed programs); never self-restart
-APP_VERSION = "0.0.22"                   # firmware version (the A/B updater pushes/compares this)
+APP_VERSION = "0.0.23"                   # firmware version (the A/B updater pushes/compares this)
+DEVICE_ID   = "K"                        # 'K' = 52Pi kit, 'X' = Pimoroni Explorer (per docs/livesync-protocol.md and the version reply)
 try:
     import rtc                           # set from the editor's clock SysEx so the log has real timestamps
 except ImportError:
@@ -1541,8 +1542,10 @@ class App:
         if cmd == 0x01 and len(sx) >= 8 and rtc is not None:        # set clock: yr-2000, mo, dd, hh, mm, ss
             try: rtc.RTC().datetime = time.struct_time((2000 + sx[2], sx[3], sx[4], sx[5], sx[6], sx[7], 0, -1, -1))
             except Exception: pass
-        elif cmd == 0x02:                              # version query -> reply 0x03 + APP_VERSION
-            if self.midi: self.midi.write(bytes([0xF0, 0x7D, 0x03]) + APP_VERSION.encode() + bytes([0xF7]))
+        elif cmd == 0x02:                              # version query -> reply 0x03 + "<device_id>;<APP_VERSION>"
+            if self.midi:                              # old firmware sent bare APP_VERSION; editor parses "contains ';'?" for back-compat
+                payload = DEVICE_ID + ";" + APP_VERSION
+                self.midi.write(bytes([0xF0, 0x7D, 0x03]) + payload.encode() + bytes([0xF7]))
         elif cmd == 0x40 or cmd == 0x41 or cmd == 0x42 or cmd == 0x43:   # Live sync (see src/livesync.js)
             try: text = "".join(chr(b) if 0x20 <= b < 0x7F else "" for b in sx[2:])
             except Exception: return

pico-explorer/README.md

@@ -0,0 +1,74 @@
+# PM_X-1 "Explorer" — CircuitPython edition (Pimoroni Explorer · RP2350)
+
+The **CircuitPython** firmware for the [Pimoroni Explorer Kit (PIM744)](https://shop.pimoroni.com/products/explorer),
+set up as a self-contained appliance. Sibling to the PM_K-1 build in `../pico-cp/` (the 52Pi EP-0172
+kit) — same engine, same program strings, same `programs.json`, same web editor.
+
+This board is a **2.8″ ST7789V 320×240 LCD + 6 user buttons (A/B/C on the left, X/Y/Z on the right)
++ piezo speaker** built around an RP2350B (Pico 2 class chip). **No touchscreen, no joystick, no
+RGB LED.** Editing is done in the web editor with **Live sync** on; the device mirrors changes in
+real time and emits its own play/stop/bpm/sel deltas back.
+
+## Controls
+
+| Button | Action                                                                |
+| ------ | --------------------------------------------------------------------- |
+| **A**  | play / stop                                                           |
+| **B**  | tap tempo                                                             |
+| **C**  | menu (Settings / Help / About / Practice log)                         |
+| **X**  | prev track (hold to repeat)                                           |
+| **Y**  | tempo −1 (hold to repeat; after ~1.5 s the step grows to −5)          |
+| **Z**  | next track (hold to repeat)                                           |
+| **X + Z** | tempo +1 (chord; same hold-repeat as Y)                            |
+
+In a menu: **X / Z** move the cursor up / down, **Y** decrements the focused value, **A** commits or
+cycles, **B** = back, **C** = close.
+
+## Install
+
+1. **Flash CircuitPython for Pico 2 / RP2350.** Hold **BOOTSEL** on the Explorer, plug it in over
+   USB-C, drop the [Pimoroni Explorer (RP2350) CircuitPython `.uf2`](https://circuitpython.org/board/pimoroni_explorer2350/)
+   onto the `RP2350` drive. A `CIRCUITPY` drive appears.
+2. **Copy the bundle onto `CIRCUITPY`** — `boot.py`, `code.py`, **`app.mpy`**, `programs.json`,
+   `font_s.bin` / `font_m.bin` / `font_l.bin`, `logo.bin` / `midi.bin` / `usb.bin`, `editor.html`
+   (offline editor). If an old `app.py` is on the drive, delete it.
+3. **Power-cycle.** It boots into appliance mode and runs.
+
+## Program it from the web
+
+Open <https://metronome.varasys.io> in Chrome / Edge / Firefox. The set-list **⋯** menu →
+**📟 Save to device** pushes a `programs.json` over USB-MIDI; the device persists it and reloads.
+Click **🔗 Live sync** to mirror edits in real time.
+
+## Pin reference
+
+The display, buttons, and audio are wired into the board — no jumpers required. CircuitPython's
+official board definition for `pimoroni_explorer2350` exposes `board.DISPLAY` pre-initialized, so
+the firmware just uses it.
+
+| Function          | GPIO     |
+| ----------------- | -------- |
+| Button A          | GP16     |
+| Button B          | GP15     |
+| Button C          | GP14     |
+| Button X          | GP17     |
+| Button Y          | GP18     |
+| Button Z          | GP19     |
+| Piezo audio (PWM) | GP12     |
+| Piezo amp enable  | GP13     |
+| I²C SDA (QwSTEMMA) | GP20    |
+| I²C SCL (QwSTEMMA) | GP21    |
+| Display           | `board.DISPLAY` (8080 parallel bus on GP26..GP39, initialized by board.c) |
+
+## Calibration (flags at the top of `app.py`)
+
+- **Speaker too loud / quiet:** the piezo + amp gain is fixed in hardware. `MUTE_SPEAKER`
+  silences the click; `SPEAKER_AUTO_MUTE` auto-mutes when a MIDI host is listening.
+- **Buttons feel inverted:** the polarity is hard-coded to active-low (pull-up). If a button
+  fires on release instead of press, check the `BTN_*` pin map at the top of `app.py`.
+- **Display orientation:** the board's CircuitPython init mounts the panel landscape
+  (320 × 240). If your screen looks rotated, that's a board.c-level thing — file a CircuitPython
+  bug, don't patch the firmware.
+
+If `app.py` ever errors, CircuitPython prints the traceback **on the screen and over USB serial** —
+send me that.

pico-explorer/boot.py

@@ -0,0 +1,22 @@
+# boot.py - runs once at power-on (before USB connects); decides who owns the filesystem.
+#
+# DEFAULT = appliance mode: the FIRMWARE owns the drive, so it can save your practice log to
+# /history.json and write /programs.json that the editor pushes over USB-MIDI. The drive is then
+# READ-ONLY to the computer - which also protects the firmware from accidental deletion.
+#
+# HOLD BUTTON A (GP16 on the Pimoroni Explorer) WHILE PLUGGING IN = editor mode: the drive is
+# writable by the computer, so you can drag programs.json / code.py on from any OS or browser
+# (the universal fallback). Reset afterwards to return to appliance mode.
+#
+# Also frees a USB endpoint (disables unused HID) and makes sure USB-MIDI is available.
+import board, digitalio, storage, usb_hid, usb_midi
+try: usb_hid.disable()
+except Exception: pass
+usb_midi.enable()
+a = digitalio.DigitalInOut(board.GP16)
+a.switch_to_input(pull=digitalio.Pull.UP)
+appliance = a.value            # value True (pull-up, not pressed) -> appliance mode
+a.deinit()
+if appliance:
+    try: storage.remount("/", readonly=False)   # writable by code, read-only to the computer
+    except Exception: pass

pico-explorer/code.py

@@ -0,0 +1,24 @@
+# code.py - PM_X-1 A/B firmware loader (stable; rarely changes).
+#
+# The real application is the PRECOMPILED app.mpy (CircuitPython compiles a big .py at boot, which
+# fragments the heap and OOMs; a .mpy loads without compiling). app.bak holds the previous known-good
+# build. The web editor pushes a new app.mpy to a "trial" slot over USB-MIDI; this loader runs it, and
+# if it fails to boot it AUTOMATICALLY ROLLS BACK to app.bak. (Unbrickable: BOOTSEL -> drag a .uf2.)
+# app.mpy clears the /trial marker once it has run healthily for ~5s.
+import supervisor, os
+supervisor.runtime.autoreload = False     # updates reboot explicitly; never auto-restart on our own writes
+
+def _trial():
+    try: os.stat("/trial"); return True
+    except OSError: return False
+
+try:
+    import app                            # runs the application (app.mpy; ends with App().run())
+except Exception:
+    if _trial():                          # a freshly-pushed build crashed on startup -> roll back
+        try:
+            os.remove("/app.mpy"); os.rename("/app.bak", "/app.mpy"); os.remove("/trial")
+        except Exception: pass
+        supervisor.reload()               # reboot into the restored known-good build
+    else:
+        raise                             # the active build failed unexpectedly (rare) -> on-screen traceback

pico-explorer/programs.json

@@ -0,0 +1,3 @@
+{
+  "setlists": []
+}