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docs(hardware): clarify TC2 physical-vs-BCM pin mapping and validation

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Seth
2026-03-11 21:30:25 +00:00
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HARDWARE.md
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@@ -39,13 +39,16 @@ Unknowns are marked `TBD` instead of guessed.
- Raspberry Pi drives each relay channel independently. - Raspberry Pi drives each relay channel independently.
- Thermocouple boards are connected to Pi GPIO. - Thermocouple boards are connected to Pi GPIO.
## GPIO Wiring (User-Confirmed) ## GPIO Wiring (Clarified)
- Thermocouple channel 1 GPIO lines: `GPIO 5`, `GPIO 8`, `GPIO 7`. - Thermocouple channel 1 (as originally noted): `GPIO 5`, `GPIO 8`, `GPIO 7` (BCM numbering).
- Thermocouple channel 2 GPIO lines: `GPIO 11`, `GPIO 12`, `GPIO 13`. - Thermocouple channel 2 was written as `11,12,13`; this has been clarified as **physical header pins**.
- Channel 2 thermocouple mapping corresponds line-for-line to channel 1 mapping (`5/8/7` -> `11/12/13`). - Thermocouple channel 2 validated mapping:
- Relay control (channel 2): `GPIO 9`. - Physical pins `11,12,13` => BCM `17,18,27`.
- Read test on BCM `17,18,27` returns valid MAX6675 words with open-thermocouple fault bit set when probe is disconnected (expected).
- Alternate interpretation (BCM `11,12,13`) returned all-zero frames and appears incorrect for channel 2.
- Relay control (channel 2): `GPIO 9` (BCM).
- `TBD`: confirm relay control GPIO for channel 1 in this dual-channel prototype wiring doc. - `TBD`: confirm relay control GPIO for channel 1 in this dual-channel prototype wiring doc.
- Note: these dual-channel GPIO assignments differ from the current single-channel `piNail2/config.json` runtime pins. - Note: these dual-channel assignments differ from the current single-channel `piNail2/config.json` runtime pins.
## Monitor Subsystem ## Monitor Subsystem
- Separate 12V power supply for the built-in monitor. - Separate 12V power supply for the built-in monitor.