jamro · jamro · Sep 21, 2026 · Sep 13, 2026 · Sep 13, 2026 · Sep 13, 2026
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
@@ -55,3 +55,21 @@ jobs:
         run: npm test --prefix packages/tiny-engineer-antigravity
       - name: Claude Code package tests
         run: npm test --prefix packages/tiny-engineer-claude-code
+
+  pcb:
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install KiCad 10
+        run: |
+          sudo add-apt-repository -y ppa:kicad/kicad-10.0-releases
+          sudo apt-get update
+          sudo DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends kicad
+          kicad-cli version
+      - name: ERC / DRC / expected-nets
+        run: python3 scripts/check_pcb.py --report-dir artifacts/pcb
+      - uses: actions/upload-artifact@v4
+        if: failure()
+        with:
+          name: pcb-reports
+          path: artifacts/pcb/
diff --git a/AGENTS.md b/AGENTS.md
@@ -31,9 +31,10 @@ node scripts/expressions/test-assets.js
 npm test --prefix packages/tiny-engineer-cursor
 npm test --prefix packages/tiny-engineer-antigravity
 npm test --prefix packages/tiny-engineer-claude-code
+python3 scripts/check_pcb.py
 ```
 
-`pio test -e native` is not `pio run -e native`. Details: [docs/testing.md](docs/testing.md).
+`pio test -e native` is not `pio run -e native`. PCB checks need KiCad 10 (`python3 scripts/check_pcb.py`). Details: [docs/testing.md](docs/testing.md).
 
 Do **not** flash (`pio run -t upload`) unless the user asks.
 
@@ -70,7 +71,7 @@ Breaking rules, SemVer mapping, and examples: [CONTRIBUTING.md](CONTRIBUTING.md)
 - **Settings** — layer checklist in [docs/settings.md](docs/settings.md). Never log raw `access_token`.
 - **Integrations** — add/extend package tests; prefer short timeouts and ignore network errors so a missing robot does not stall the agent.
 - **CAD** — edit `.f3d` **and** export affected `3mf`. CERN-OHL-S. Do not swap `AiEmblem.3mf` as branding.
-- **PCB** — [docs/pcb.md](docs/pcb.md) checklist + KiCad review rules below. New board paths need `REUSE.toml`. CERN-OHL-S.
+- **PCB** — [docs/pcb.md](docs/pcb.md) checklist + KiCad review rules below. Run `python3 scripts/check_pcb.py` (KiCad 10). New board paths need `REUSE.toml`. CERN-OHL-S.
 - **Motion** — poses −1..1 mapped to saved min/max; see [docs/robot-movement.md](docs/robot-movement.md). Do not widen NVS servo clamps without testing on a real robot.
 - **Secrets** — no `.env`, tokens, or Wi-Fi passwords in logs or screenshots.
 

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
@@ -44,9 +44,10 @@ node scripts/expressions/test-assets.js
 npm test --prefix packages/tiny-engineer-cursor
 npm test --prefix packages/tiny-engineer-antigravity
 npm test --prefix packages/tiny-engineer-claude-code
+python3 scripts/check_pcb.py
 ```
 
-`pio test -e native` is not `pio run -e native`. Details: [docs/testing.md](docs/testing.md). Flash locally with `pio run -t upload` when you have a board. Physical module is a **Waveshare ESP32-C3-Zero**; PlatformIO `board = esp32-c3-devkitm-1` is the build target name.
+`pio test -e native` is not `pio run -e native`. PCB checks need KiCad 10 (`python3 scripts/check_pcb.py`). Details: [docs/testing.md](docs/testing.md). Flash locally with `pio run -t upload` when you have a board. Physical module is a **Waveshare ESP32-C3-Zero**; PlatformIO `board = esp32-c3-devkitm-1` is the build target name.
 
 ## By change type
 
@@ -60,7 +61,7 @@ npm test --prefix packages/tiny-engineer-claude-code
 
 **CAD.** Edit [`3d_models/cad/TinyEngineer.f3d`](3d_models/cad/TinyEngineer.f3d) **and** export the affected [`3d_models/parts/{servo_id}/3mf/*.3mf`](3d_models/parts/). Keep CERN-OHL-S. Do not swap `AiEmblem.3mf` as a branding change.
 
-**PCB.** Follow the [PCB checklist](docs/pcb.md#checklist). Keep [`expected-nets.yml`](docs/pcb.md#expected-nets-yml) in sync. One board per `hardware/boards/<name>/`, KiCad 10, ERC and DRC reviewed, no generated Gerbers or other fab outputs. Keep CERN-OHL-S. New board paths need a matching `[[annotations]]` block in [REUSE.toml](REUSE.toml).
+**PCB.** Follow the [PCB checklist](docs/pcb.md#checklist). Run `python3 scripts/check_pcb.py` before opening a PCB PR. Keep [`expected-nets.yml`](docs/pcb.md#expected-nets-yml) in sync. One board per `hardware/boards/<name>/`, KiCad 10, ERC and DRC reviewed, no generated Gerbers or other fab outputs. Keep CERN-OHL-S. New board paths need a matching `[[annotations]]` block in [REUSE.toml](REUSE.toml).
 
 **Motion.** Animations use −1..1 poses mapped to the saved min/max in [docs/robot-movement.md](docs/robot-movement.md). Stock defaults live in [`include/servos.h`](include/servos.h). Do not widen NVS servo clamps without testing on a real robot. Setup AP `POST /setup/servo` can use 0–180° to find limits; assembled motion must not.
 

diff --git a/REUSE.toml b/REUSE.toml
@@ -26,6 +26,11 @@ path = "hardware/boards/**"
 SPDX-FileCopyrightText = "2026 Krzysztof Jamroz"
 SPDX-License-Identifier = "CERN-OHL-S-2.0"
 
+[[annotations]]
+path = "hardware/boards/main-control-board/**"
+SPDX-FileCopyrightText = "2026 Krzysztof Jamroz"
+SPDX-License-Identifier = "CERN-OHL-S-2.0"
+
 [[annotations]]
 path = "hardware/LICENSE"
 SPDX-License-Identifier = "CERN-OHL-S-2.0"

diff --git a/docs/hardware/components.md b/docs/hardware/components.md
@@ -54,7 +54,7 @@ Constants cited below match [`include/pins.h`](../../include/pins.h).
 | Interface | I2C |
 | Address | `0x40` (`PCA9685_ADDRESS` in firmware). A0–A5 pads can change this |
 | PWM | 12-bit, firmware `setPWMFreq(50)` |
-| Important pins | As drawn: **5V** (servo-rail in), **V+** (to servo 5V), **VCC** (3V3 logic), **GND**, **SDA**, **SCL**, **PWM**. OE not drawn |
+| Important pins | As drawn: **5V** (servo-rail in), **V+** (to servo 5V), **VCC** (3V3 logic), **GND**, **SDA**, **SCL**, **PWM**. **OE** (GP5) is pending, not implemented |
 | Channels used | 0–4 (five servos). 5–15 unused |
 | Limits | **V+** and **VCC** must stay separate. Do not jumper servo power onto logic VCC on this robot |
 | Firmware note | Detection at `0x40` is a **hard fail** in the bring-up test |

diff --git a/docs/hardware/interfaces.md b/docs/hardware/interfaces.md
@@ -57,13 +57,13 @@ Generated by **PCA9685**, not by ESP32 LEDC/MCPWM.
 
 ESP32 GPIO is not wired to servo SIG lines.
 
-### PCA9685 output enable (optional)
+### PCA9685 output enable
 
 | Signal | ESP32 GPIO | Notes |
 | --- | --- | --- |
 | OE | GPIO5 / GP5 | **Active LOW** — outputs enabled. Firmware drives **HIGH** during PCA9685 init, then **LOW** after neutral PWM is written |
 
-Controlled only when `PCA9685_OE_WIRED = true` in [`include/pins.h`](../../include/pins.h). Default `false`: OE pin unused (Adafruit breakout pull-down keeps outputs enabled). Wire GP5 → PCA9685 **OE** and set the flag to block invalid PWM during boot and flash resets.
+Not wired (`PCA9685_OE_WIRED = false` in [`include/pins.h`](../../include/pins.h)). Firmware keeps OE helpers behind that flag. Blocks invalid PWM during boot and flash resets when the net exists.
 
 ## USB
 

diff --git a/docs/hardware/pinout.md b/docs/hardware/pinout.md
@@ -11,7 +11,7 @@ Source of truth: [`include/pins.h`](../../include/pins.h). This file must match
 | I2S BCLK | **GPIO2** (diagram **GP2**) | `I2S_BCLK` | MAX98357A BCLK |
 | I2S LRCLK / WS | **GPIO3** (diagram **GP3**) | `I2S_LRC` | MAX98357A **LRC** |
 | I2S DATA OUT | **GPIO4** (diagram **GP4**) | `I2S_DIN` | MAX98357A DIN |
-| PCA9685 OE (optional) | **GPIO5** (diagram **GP5**) | `PCA9685_OE_PIN` | PCA9685 **OE** when `PCA9685_OE_WIRED` |
+| PCA9685 OE | **GPIO5** (diagram **GP5**) | `PCA9685_OE_PIN` | reserved for PCA9685 **OE**; net pending (`PCA9685_OE_WIRED`) |
 | Built-in WS2812 RGB | **GPIO10** | `RGB_LED_PIN` | onboard LED only |
 
 Logic level: **3.3 V**.
@@ -30,7 +30,6 @@ Logic level: **3.3 V**.
 
 | GPIO | Status | Notes |
 | --- | --- | --- |
-| GPIO5 | **Optional** | PCA9685 **OE** when wired; set `PCA9685_OE_WIRED = true` in `pins.h` |
 | GPIO6 | Free | Unused |
 | GPIO7 | Free | Unused |
 | GPIO8 | Free | Unused |
@@ -60,7 +59,7 @@ Power pads (not GPIO): **5V**, **GND**, **3V3**.
 | `OLED_WIDTH` / `OLED_HEIGHT` | 128 / 32 | Display |
 | `SERVO_MIN_US` / `SERVO_MAX_US` | 800 / 2200 | Electrical PWM span |
 | `SERVO_BOOT_SPEED_DEG_S` | 35 | Boot centering / sleep-pose rate (deg/s) |
-| `PCA9685_OE_WIRED` | `false` | Set `true` after wiring GP5 → PCA9685 OE |
+| `PCA9685_OE_WIRED` | `false` | pending GP5 → PCA9685 OE (not on schematic/PCB yet) |
 
 ## Pin allocation rules
 

diff --git a/docs/hardware/servos.md b/docs/hardware/servos.md
@@ -48,12 +48,12 @@ Verified in [`include/pins.h`](../../include/pins.h) and [`include/servos.h`](..
 
 On every boot (and after each flash reset):
 
-1. **Optional OE** — if `PCA9685_OE_WIRED`, GP5 disables PCA9685 outputs before I2C init.
+1. **OE** — `PCA9685_OE_WIRED` is false until a tested GP5→OE board exists; firmware skips the OE pin.
 2. **Early init** — PCA9685 is probed and configured immediately after `Wire.begin`, before OLED, settings, or Wi-Fi.
-3. **Neutral park** — all channels receive mid-pulse PWM while OE is still disabled (if wired), then outputs enable.
+3. **Neutral park** — all channels receive mid-pulse PWM (OE enable is skipped while unwired).
 4. **Smooth boot moves** — `centerAllServos()` and sleep-inertia pose use `servoMoveAllSmoothTo()` at `SERVO_BOOT_SPEED_DEG_S` (35°/s), not instant snaps.
 
-Set `PCA9685_OE_WIRED = true` in [`include/pins.h`](../../include/pins.h) after wiring GP5 → PCA9685 **OE**. OE is **active LOW** on the Adafruit breakout.
+GP5 → PCA9685 **OE** is planned, not implemented (`PCA9685_OE_WIRED = false` in [`include/pins.h`](../../include/pins.h)). OE is **active LOW** on the Adafruit breakout when that net exists.
 
 ## Idle and sleep PWM release
 

diff --git a/docs/hardware/testing.md b/docs/hardware/testing.md
@@ -19,7 +19,7 @@ Build/flash: [flash.md](../flash.md) (`pio run`, `pio run -t upload`, serial 115
 | --- | --- |
 | Built-in WS2812 | Green ready (GPIO10) |
 | I2C init | `Wire.begin` on GPIO0/GPIO1 |
-| PCA9685 | Probe `0x40` early; park neutral; optional OE on GP5 |
+| PCA9685 | Probe `0x40` early; park neutral; OE skipped (`PCA9685_OE_WIRED` is false until GP5→OE is implemented) |
 | OLED | Probe `0x3C`, init (optional) |
 | Wi-Fi | STA connect from saved NVS credentials, or setup AP `TinyEngineer-XXXX` when unset/failed; mDNS `{hostname}.local` after STA connect |
 | MAX98357A / I2S | `I2S.begin` 44.1 kHz 16-bit stereo |

diff --git a/docs/hardware/wiring.md b/docs/hardware/wiring.md
@@ -66,7 +66,6 @@ On Adafruit PCA9685, header/terminal **V+** is normally the same servo rail as t
 | ESP32-C3-Zero | GP2 | MAX98357A | BCLK | I2S bit clock |
 | ESP32-C3-Zero | GP3 | MAX98357A | LRC | I2S word select |
 | ESP32-C3-Zero | GP4 | MAX98357A | DIN | I2S data |
-| ESP32-C3-Zero | GP5 | PCA9685 | OE | Optional output enable (see [interfaces.md](interfaces.md)) |
 | PCA9685 | PWM | Servo | SIG | Servo PWM |
 | PCA9685 | V+ | Servo | 5V | Servo power |
 | PCA9685 | GND (servo side) | Servo | GND | Servo ground |
@@ -142,11 +141,11 @@ Firmware drives **channels 0–4** (`SERVO_SPECS` / `SERVO_HEAD`…`SERVO_BODY`)
 
 ESP32-C3-Zero, unused in the PNG:
 
-**GP6, GP7, GP8, GP9, GP10, GP20, GP21**
+**GP5, GP6, GP7, GP8, GP9, GP10, GP20, GP21**
 
-GP5 = optional PCA9685 OE (not in PNG). GP9 = BOOT, GP10 = onboard WS2812. GP18/GP19 = native USB — wire from 5993 D−/D+ even if the base PNG omits them. See [pinout.md](pinout.md).
+GP5 is reserved for PCA9685 OE (`PCA9685_OE_PIN`) but that net is **pending**: schematic and PCB do not implement or validate GP5→OE yet (`PCA9685_OE_WIRED = false`). GP9 = BOOT, GP10 = onboard WS2812. GP18/GP19 = native USB — wire from 5993 D−/D+ even if the base PNG omits them. See [pinout.md](pinout.md).
 
-PCA9685 **OE** optional on GP5 — not drawn on base PNG. MAX98357A **GAIN** / **SD** not wired (breakout defaults). **SPK+** / **SPK-** not drawn.
+PCA9685 **OE** is not wired on this board. MAX98357A **GAIN** / **SD** not wired (breakout defaults). **SPK+** / **SPK-** not drawn.
 
 ## Not on the drawing
 

diff --git a/docs/pcb.md b/docs/pcb.md
@@ -4,7 +4,7 @@ Baseline for contributing KiCad PCB designs. Goal: boards that are easy to under
 
 Before opening a PR, run the [checklist](#checklist).
 
-Workflow and automated validation are still evolving. A reference board and CI pipeline are in progress and will be used to validate these rules.
+Workflow and automated validation: CI runs ERC, DRC, and `expected-nets.yml` via `python3 scripts/check_pcb.py` (see [testing.md](testing.md)).
 
 KiCad sources live in [`hardware/boards/`](../hardware/README.md). Robot electrical reference (pinout, wiring, BOM) stays in [`docs/hardware/`](hardware/README.md). Firmware drivers stay in `src/hardware/`.
 
@@ -108,27 +108,33 @@ Before submitting or updating a hardware pull request:
 
 The project should not introduce unexplained ERC or DRC errors.
 
-Automated ERC and DRC via GitHub Actions is planned and is being tested on a reference board. It is not required yet.
+Run the same checks CI uses (KiCad 10, stdlib Python — no pip packages):
+
+```bash
+python3 scripts/check_pcb.py
+```
+
+Errors fail; warnings do not. Reports go to a temp dir, or pass `--report-dir artifacts/pcb`. CI runs this on every push/PR ([`.github/workflows/ci.yml`](../.github/workflows/ci.yml)).
 
 ## expected-nets.yml
 
 Committed checklist of **critical** net → pin memberships for human/AI review. Not a full netlist dump.
 
 - **Path:** `hardware/boards/<board-name>/expected-nets.yml`
-- **Check:** `kicad-cli sch export netlist`, then compare to this file. No `kicad-cli` → say so and skip connectivity claims ([AGENTS.md](../AGENTS.md)).
+- **Check:** `python3 scripts/check_pcb.py` (exports netlist via `kicad-cli` and compares). Manual: `kicad-cli sch export netlist`, then compare to this file. No `kicad-cli` → say so and skip connectivity claims ([AGENTS.md](../AGENTS.md)).
 - **Do not** infer nets from `.kicad_sch` / `.kicad_pcb` coordinates or geometry.
 - **Update** when you intentionally change listed nets or pins. Keep the list to power and important buses (I2C, I2S, USB, …), not every net.
 
-Minimal shape (pin tokens = KiCad netlist `RefDes.PinName`):
+Minimal shape (pin tokens = KiCad netlist `RefDes.PinNum:PinName` — pin number plus symbol pin name, so duplicate names like multiple `GND` pins stay distinct):
 
 ```yaml
 nets:
   "+5V":
-    - ESP1.5V
-    - PCA1.V+
+    - ESP1.1:5V
+    - PCA1.6:V+
   GND:
-    - ESP1.GND
-    - PCA1.GND
+    - ESP1.2:GND
+    - PCA1.1:GND
 ```
 
 Required for new or updated boards when claiming connectivity in a PR.
@@ -211,8 +217,7 @@ Use this before opening or updating a PCB pull request. Details are in the secti
 
 **Quality and docs**
 
-- [ ] ERC run; violations reviewed
-- [ ] DRC run; violations reviewed
+- [ ] ERC / DRC / expected-nets: `python3 scripts/check_pcb.py` passes (or GUI ERC+DRC reviewed if no `kicad-cli`; do not claim connectivity or net checks without `kicad-cli`)
 - [ ] No suppressions used only to make checks pass; any intentional exception has a reason
 - [ ] `expected-nets.yml` present and matches current netlist for listed nets
 - [ ] Board `README.md` covers purpose, status, interfaces, assumptions, and whether this revision was manufactured and tested
@@ -233,17 +238,15 @@ Existing in-progress PRs: align where reasonably possible. Do not redesign solel
 
 The requirements above are the current contribution baseline.
 
-Not standardized yet (to be evaluated on the reference board):
+Not standardized yet:
 
-- automated KiCad ERC and DRC in GitHub Actions
-- exact multi-board CI structure
 - manufacturing jobsets
 - automated manufacturing artifacts
 - release and prerelease manufacturing packages
 - shared KiCad libraries
 - automated PCB renders or visual diffs
 - manufacturer-specific output configurations
 
-Once the reference implementation is validated, this page will be updated. Stable parts of the workflow may become required for new hardware contributions.
+ERC, DRC, and `expected-nets.yml` checks run in CI via `python3 scripts/check_pcb.py`.
 
 Keep the workflow reproducible and safe. Avoid complexity until it solves a real problem.
diff --git a/docs/testing.md b/docs/testing.md
@@ -1,6 +1,6 @@
 # Tests
 
-Host checks. These commands do not flash the board. GitHub Actions on `main` and PRs runs these same commands. On-device hardware: [hardware/testing.md](hardware/testing.md).
+Host checks. These commands do not flash the board. GitHub Actions on `main` and PRs runs these same commands (firmware, packages, and PCB). On-device hardware: [hardware/testing.md](hardware/testing.md).
 
 ## Firmware
 
@@ -34,3 +34,13 @@ npm test --prefix packages/tiny-engineer-cursor
 npm test --prefix packages/tiny-engineer-antigravity
 npm test --prefix packages/tiny-engineer-claude-code
 ```
+
+## PCB
+
+KiCad 10 (`kicad-cli`). Stdlib Python only — no pip packages. ERC (errors), DRC (errors + schematic parity), and `expected-nets.yml` for every board under `hardware/boards/`.
+
+```bash
+python3 scripts/check_pcb.py
+```
+
+Optional: `python3 scripts/check_pcb.py main-control-board --report-dir artifacts/pcb`. Details: [pcb.md](pcb.md). On-device hardware: [hardware/testing.md](hardware/testing.md).
diff --git a/hardware/.gitignore b/hardware/.gitignore
@@ -0,0 +1,4 @@
+*.bak
+gerbers/
+production/
+fabrication-toolkit-options.json
diff --git a/hardware/README.md b/hardware/README.md
@@ -4,7 +4,11 @@ KiCad PCB projects for Tiny Engineer.
 
 Boards live under `boards/<board-name>/`. Prefer the same name for the directory and the KiCad project.
 
-Contribution rules, KiCad version, what to commit, ERC/DRC, and PR expectations: [docs/pcb.md](../docs/pcb.md). Pre-PR checklist: [docs/pcb.md#checklist](../docs/pcb.md#checklist). Critical net checklist: [docs/pcb.md#expected-nets-yml](../docs/pcb.md#expected-nets-yml).
+| Board | Role |
+| --- | --- |
+| [`main-control-board`](boards/main-control-board/) | Draft interconnect / carrier (header sockets for existing modules) |
+
+Contribution rules, KiCad version, what to commit, ERC/DRC, and PR expectations: [docs/pcb.md](../docs/pcb.md). Pre-PR checklist: [docs/pcb.md#checklist](../docs/pcb.md#checklist). Critical net checklist: [docs/pcb.md#expected-nets-yml](../docs/pcb.md#expected-nets-yml). Local/CI checks: `python3 scripts/check_pcb.py` (KiCad 10) — [docs/testing.md](../docs/testing.md).
 
 This tree is KiCad source only. Robot electrical reference (pinout, wiring, BOM) is [`docs/hardware/`](../docs/hardware/README.md). Firmware drivers are `src/hardware/`.
 

diff --git a/hardware/boards/main-control-board/README.md b/hardware/boards/main-control-board/README.md
@@ -0,0 +1,20 @@
+# main-control-board
+
+Carrier PCB that reduces jumper wiring: existing modules plug in on pin headers.
+
+- **Purpose:** interconnect / carrier with header sockets for the existing modules
+- **Status:** draft (schematic + routed layout, rev v1 / 2026-09-12)
+- **KiCad:** 10
+- **Interfaces:** header sockets for the Waveshare ESP32-C3-Zero, Adafruit PCA9685, MAX98357A, SSD1306 OLED, and Adafruit 5993 USB-C breakout; shared I2C (ESP32 GP0/GP1 → PCA9685 and SSD1306 OLED); point-to-point I2S (ESP32 GP2/GP3/GP4 → MAX98357A BCLK/LRC/DIN); USB D+/D− (5993 → ESP32 GP19/GP18); PCA9685 OE ← GP5; +5V, 3V3, and GND. Servo 3-pin plugs and speaker terminals stay on the modules this revision.
+- **Assumptions:** nets follow [`docs/hardware/`](../../../docs/hardware/README.md) (keep servo **+5V** off logic **3V3**; common GND). Custom module symbols live in [`libraries/symbols/tiny_engineer_modules.kicad_sym`](libraries/symbols/tiny_engineer_modules.kicad_sym); footprints in [`libraries/footprints/tiny_engineer_modules.pretty`](libraries/footprints/tiny_engineer_modules.pretty). ESP32-C3-Zero symbol pin numbers are Waveshare **header pads** (pad 1 = 5V, numbered anticlockwise from USB), not the ESP32-C3 QFN package. Two-layer FR4 ~1.6 mm; ESP32-C3-Zero on the back, other modules on the front. OLED uses a 1×04 pin header; USB-C breakout uses a 1×04 pin socket. Netclasses: `GND`, `Power5V` (`+5V`, 1.5 mm), `Power3V3` (`+3.3V`, 0.4 mm), `USB` (`/USB_`*), `Default` (I2C/I2S and other signals).
+- **ERC / DRC:** ERC passed; DRC passed (custom rules in `main-control-board.kicad_dru`)
+- **Built:** not manufactured
+- **Tested:** not tested
+
+## Direction
+
+First revision is sockets only. Design in KiCad 10, then fabricate, so the robot is wired on a board instead of Dupont harnesses.
+
+Later revisions may integrate some or all of those functions onto this PCB and drop the plug-in modules.
+
+Contribution rules: [`docs/pcb.md`](../../../docs/pcb.md).