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[P0] Orin-FC UART wiring disconnected - USART6 (PC6/PC7) not reaching Orin GPIO 8/10 #356

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opened 2026-03-03 13:48:34 -05:00 by seb · 0 comments
seb commented 2026-03-03 13:48:34 -05:00
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Problem

Jetson Orin UART (ttyTHS1, pins 8/10) cannot communicate with FC USART6 (PC6=TX, PC7=RX). Zero bytes in both directions.

Diagnosis (2026-03-03)

What works

  • FC firmware running (confirmed via USB ttyACM0)
  • USB telemetry streams clean JSON
  • FC USART6 TX active (txc counter incrementing)
  • Orin UART hardware functional

What fails

  • Orin receives 0 bytes on ttyTHS1 AND ttyTHS2 (all baud rates)
  • FC rxc stays static when Orin sends data
  • Both directions broken = physical wiring issue

FC UART Config

  • jlink.c uses USART6: PC6=TX, PC7=RX, 921600 baud
  • Board pads: T6/R6 on MAMBA F722S
  • NOTE: main.c:157 comment says USART1 but code is USART6 - fix comment

Orin UART Config

  • Pin 8 = TX, Pin 10 = RX = /dev/ttyTHS1

Action Required

  1. Verify wires on T6/R6 pads (not T1/R1)
  2. Check solder joints
  3. Confirm TX-RX crossover (FC TX to Orin RX, FC RX to Orin TX)
  4. Verify shared GND
  5. Fix misleading comment in main.c line 157
## Problem Jetson Orin UART (ttyTHS1, pins 8/10) cannot communicate with FC USART6 (PC6=TX, PC7=RX). Zero bytes in both directions. ## Diagnosis (2026-03-03) ### What works - FC firmware running (confirmed via USB ttyACM0) - USB telemetry streams clean JSON - FC USART6 TX active (txc counter incrementing) - Orin UART hardware functional ### What fails - Orin receives 0 bytes on ttyTHS1 AND ttyTHS2 (all baud rates) - FC rxc stays static when Orin sends data - Both directions broken = physical wiring issue ## FC UART Config - jlink.c uses USART6: PC6=TX, PC7=RX, 921600 baud - Board pads: T6/R6 on MAMBA F722S - NOTE: main.c:157 comment says USART1 but code is USART6 - fix comment ## Orin UART Config - Pin 8 = TX, Pin 10 = RX = /dev/ttyTHS1 ## Action Required 1. Verify wires on T6/R6 pads (not T1/R1) 2. Check solder joints 3. Confirm TX-RX crossover (FC TX to Orin RX, FC RX to Orin TX) 4. Verify shared GND 5. Fix misleading comment in main.c line 157
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Reference: seb/saltylab-firmware#356
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