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Update firmware over CAN

How-to. Satellites (XIAO ESP32-S3) accept a new image over the bus; no USB cable needed. Masters and the standalone v4 cannot be updated this way.

Mechanism: SDO block download into object 0x2F00, CRC-32 check, reboot into the new partition (objects). Image: the app-only binary (firmware.bin from pio run -e <env>, or esp32_<env>.bin from the FRAME firmware server), max 1.25 MB. The web-flasher release images are full images (bootloader + partitions + app) and cannot be used for OTA.

Option A: through the HAT+ master (serial)​

Needs UC2_canopen_master on the HAT+ (921600 Bd).

import uc2rest

esp = uc2rest.UC2Client(serialport="/dev/ttyUSB0", baudrate=921600)
ok = esp.canota.start_can_streaming_ota_blocking(
    can_id=12,
    firmware_path="esp32_UC2_canopen_slave_motor_release.bin",
    progress_callback=lambda chunk, total, sent, speed: print(f"{chunk}/{total}"),
)
print("success" if ok else "failed")

What happens on the wire: /ota_start → {"ota_status":"ready","chunkSize":4096} → raw 4 KB chunks, each acked with {"ota_rx":n} → {"ota_status":"flashing"} → {"ota_status":"success"}. The serial link is busy for the whole transfer.

Option B: directly from the Pi or a PC (python-canopen)​

Uses the firmware repo's tool, which supports block transfer:

pip install canopen python-can
python uc2-ESP/tools/canopen/uc2_ota_can.py --node 12 \
    --binary esp32_UC2_canopen_slave_motor_release.bin \
    --interface socketcan --channel can0 --bitrate 500000

uc2canopen cannot do this; it supports expedited SDO only.

Check the result​

The node reboots ~2 s after the transfer. Then:

{"task":"/can_act","scan":true}

fwVersion / fwImage of node 12 show the new build. On failure, read 0x2F05 (1 no partition, 2 begin, 3 write, 4 CRC, 5 commit, 6 size 0, 7 too large).

warning

Keep the bus quiet during the update: no motion commands through the master, no uc2canopen traffic to the same node. A transfer idle for 30 s is aborted; the old firmware keeps running.