Flash Expansion Board

Flash and debug firmware on the Expansion Board

The expansion board has a built-in RP2040-based programmer that is pre-flashed with debugprobe firmware that allows it to function as a CMSIS-DAP probe. This makes it easy to flash new firmware onto the FC board over USB using standard tools such as probe-rs or OpenOCD.

Building the expansion boards default firmware

Clone the elodin repository and navigate to the fsw directory:

git clone https://github.com/elodin-sys/elodin.git
cd elodin/fsw

The fsw directory contains several example projects, navigate into the sensor-fw directory & follow the build instructions there. The last step is the command cargo rrb fw, which will build the firmware and flash it to the FC board. You should see the same sensor output as before when connected to the Base Board, or alternatively can follow the instructions in the sensor-fw directory readme to collect sensor data from the included SD card.

aleph-flash-fc

Flashing from the Orin NX via deploy.sh

Aleph can also flash the STM32H7 from the Orin NX during a normal NixOS deploy. This is the preferred bring-up path for fsw/c-blinky because it packages the firmware into the Aleph closure, deploys it to the target, flashes it over the board-to-board link, and forwards the MCU log output into Elodin-DB.

From the aleph/ directory:

nix build --accept-flake-config .#packages.aarch64-linux.toplevel --show-trace
./deploy.sh -h 192.168.4.188 -u root

The deploy activates a c-blinky-flash one-shot service on Aleph. That service:

  1. Uses the packaged firmware.bin from the deployed closure
  2. Stops serial-bridge so /dev/ttyTHS1 is free for flashing
  3. Drives BOOT0 over carrier GPIO9 and pulses NRST over carrier GPIO11
  4. Configures /dev/ttyTHS1 for 19200 8E1
  5. Probes the STM32 ROM UART bootloader with stm32flash
  6. Writes the application image to 0x08000000
  7. Resets the STM32 back into the flashed application
  8. Starts serial-bridge again so Linux can ingest the MCU logs

The open-source expansion board uses the direct GPIO11 reset path above. The older custom reference board used an I2C expander for NRST, so bring-up notes from that flow need to be translated accordingly.

Verifying the Flash

On the Aleph host, check the flash service:

journalctl -u c-blinky-flash -n 50 --no-pager

Then confirm the serial bridge is receiving the MCU log frames:

journalctl -u serial-bridge -n 50 --no-pager

If the flash unit reports Timed out waiting for STM32 bootloader on /dev/ttyTHS1, the STM32 did not answer the ROM bootloader probe and the board-to-board flashing path still needs hardware-level debugging on that Aleph.

c-blinky emits INFO log messages such as c-blinky boot, LED: ON, and LED: OFF over the board-to-board UART.

Viewing Logs in the Editor

serial-bridge forwards the MCU lines into Elodin-DB as LogEntry messages on the aleph.stm32.log stream.

Open the Editor against the Aleph database and add a log panel such as:

log_stream "aleph.stm32.log" name="STM32 c-blinky"

You should see the c-blinky boot message followed by alternating LED: ON and LED: OFF entries.

Manual Flashing on Aleph

If you need to bypass deploy-driven flashing and run the tool directly on the Orin NX:

sudo flash-mcu --elf <elf path>
# or, if you already have a raw binary:
sudo flash-mcu --bin <bin path>
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