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system76-embedded-controller/doc/debugging.md
Tim Crawford f9a775e71b docs: Add info for logging through parport
2020-03-06 11:16:04 -07:00

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Debugging the EC firmware

Terms used:

  • target: The laptop system that has the EC to be tested
  • host: The system that will have all devices connected to it and will receive the EC logs

Parallel port

This method replaces the keyboard with a device used for debug logging. An alternate method of interacting with the target is needed; e.g., an external USB keyboard or SSH session.

Requirements:

  • Arduino Mega 2560 compatible board
  • 24 pin flexible printed circuit
    • 0.5mm or 1.0mm pitch, depending on target connector
  • 24 pin FPC breakout board with connectors
  • USB-C cable

Configuring the Mega 2560

If the breakout board did not come preassembled, assemble it before starting. This will require soldering.

  1. Connect the breakout board to the Mega 2560
    • Orientation will affect the mapping of GPIO pins
  2. Connect the Mega 2560 to the host
  3. Configure GPIO pin mapping in parallel.c based on how it will connect to the target parallel port
    • Trace pin 1 on motherboard connector to Mega's GPIO pins
  4. Build and flash the firmware for the Mega 2560
make BOARD=arduino/mega2560
make BOARD=arduino/mega2560 flash

Setup

  1. Enable parallel port debugging in the EC firmware
    • Uncomment PARPORT_DEBUG in board.mk
    • Build and flash the firmware for the target
  2. Power off target
  3. Remove bottom panel
  4. Unplug keyboard cable
    • May require removing keyboard depending on port location
  5. Connect Mega 2560 to host
    • This will create an ACM device at /dev/ttyACM*
  6. Connect to ACM device from host
sudo tio -b 1000000 -m INLCRNL /dev/ttyACM0
  1. Set Mega to peripheral mode
echo 'C' > /dev/ttyACM0
  1. Ground target to host
    • Connect USB cable from USB-C port on target to host
  2. Connect Mega 2560 to target

EC logs should now print to the console on the host. This can be tested by removing or inserting the AC adapter to trigger a power event.

To return the Mega to host mode, reset the device.

If logs are corrupted, try power cycling the Mega.

I2C connection

Failure to follow steps in order, or performing steps on an unsupported board, may result in damaged board components.

Wiring the target

These steps apply to the following models:

  • darp5
  • darp6
  • galp3-c
  • galp4
  1. Power off system
  2. Unplug AC adapter
  3. Remove bottom panel
  4. Disconnect battery
  5. Attach one wire to battery pin 4 (CLK)
  6. Attach one wire to battery pin 5 (DATA)
  7. Route wires through the Kensington lock slot
    • Secure wires to board with tape
  8. Attach female connector and housing to wires
  9. Reconnect battery
  10. Replace bottom panel

Setup

Requirements:

  • Target wired for EC debugging
  • Adafruit Trinket M0
  • USB-C cable
  1. Enable I2C debugging in the EC firmware for the target
    • Uncomment I2C_DEBUGGER in board.mk
    • Build and flash firmware
  2. Connect Trinket M0 to host
    • This will create an ACM device at /dev/ttyACM*
  3. Connect to ACM device from host
sudo tio -b 115200 -m INLCRNL /dev/ttyACM0
  1. Ground target to host
    • Connect USB cable from USB-C port on target to host
  2. Connect target to host
    • Connect CLK wire to SCL on Trinket M0
    • Connect DATA wire to SDA on Trinket M0

EC logs should now print to the console on the host. This can be tested by removing or inserting the AC adapter to trigger a power event.