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Hardware - Raspberry Pi CAN (MCP2518FD on SPI0)

The BMS GUI talks to the car over CAN FD (can-bridge uses SocketCAN FD). On the Pi this is a bare MCP2518FD on SPI0.0, shown as can0.

Match BMS FDCAN2 (GUI / Raspi FD bus): 250 kbit/s nominal / 2 Mbit/s data, BRS on. (FDCAN1 classic 500 kbit/s is a different bus. Do not use that bus here.)

Wiring (SPI0.0)

MCP2518FD Pi GPIO (BCM) Board pin
MOSI / SI 10 19
MISO / SO 9 21
SCLK 11 23
CS 8 (CE0) 24
INT 25 22
3V3 / GND 3V3 / GND 1 or 17 / 6
  • Crystal on the breakout: 40 MHz (must match the overlay oscillator=).
  • Chip SDO -> Pi MISO, SDI -> Pi MOSI (do not swap).
  • If the module has /RESET, hold it high (3V3).
  • CANH / CANL -> BMS GUI FD bus when ready. Terminate only if this node is at an end of the stub.

One-time / reproducible setup

# Idempotent: writes /boot/firmware/config.txt overlay
sudo ./scripts/setup-mcp2518fd-spi.sh

# Apply device tree
sudo reboot

# After reboot
sudo ./scripts/setup-mcp2518fd-spi.sh --status

Overlay installed (under [all] in /boot/firmware/config.txt):

dtparam=spi=on
dtoverlay=mcp251xfd,spi0-0,interrupt=25,oscillator=40000000,speed=10000000

Script helpers:

sudo ./scripts/setup-mcp2518fd-spi.sh --probe   # rebind driver -> SPI TX burst (Saleae)
sudo ./scripts/setup-mcp2518fd-spi.sh --status  # pinmux, dmesg, can0 type

Bring-up bitrate (boot)

test/setup_vcan.sh (installed as /usr/local/sbin/bms-setup-vcan by scripts/install-boot-services.sh) brings hardware can0 up as:

ip link set can0 type can bitrate 250000 dbitrate 2000000 fd on
ip link set can0 up

bms-can0.service runs that on boot before can-bridge. If the MCP2518FD is not present, boot uses vcan can0 for lab use.

Validation

SPI only (no chip on the bus)

  1. Overlay is loaded. pinctrl shows GPIO9-11 as SPI0.
  2. Run sudo ./scripts/setup-mcp2518fd-spi.sh --probe while a logic analyzer watches CE0 / SCLK / MOSI (board pins 24 / 23 / 19).
  3. Expect a short SPI burst. MISO idle is normal when nothing is connected.
  4. dmesg will report osc=0x00000000 / failed detect. This is expected without the MCP2518FD.
  5. can0 stays vcan until the chip probes successfully.

With MCP2518FD wired

sudo ./scripts/setup-mcp2518fd-spi.sh --status
# expect: mcp251xfd bound, can0 is NOT vcan
sudo /usr/local/sbin/bms-setup-vcan --can0-only
ip -details link show can0   # FD, 250000 / 2000000, UP
sudo systemctl restart can-bridge

Stop the lab gateway when you use the real bus: sudo systemctl stop bms-vcan-lab.

Saleae / logic analyzer (SPI TX check)

Channel Signal Board pin
0 SCLK 23
1 MOSI 19
2 MISO 21
3 CE0 24
4 (opt) INT 22

SPI Mode 0, MSB first, sample rate >= 20 MS/s. Arm capture, then run --probe.