reBot B601-RS on Jetson AGX Orin — built-in CAN setup

Jetson/ARM adaptation of the upstream reBot AGENTS.md guide and the vendor's B601-RS quick start (assembly, power supply, safety). Both assume a USB-CAN (PCAN) adapter; this skill uses the Orin's on-chip CAN (mttcan) instead. motorbridge only ever talks to a SocketCAN channel named can0, so the only real change is how can0 is created — everything downstream (scan, id-set, gateway, Studio) is identical.

Tested against the B601-RS (RobStride) only, not the B601-DM (Damiao). The DM build needs --vendor damiao in place of --vendor robstride, and motorbridge reaches Damiao hardware over its dm-serial / dm-device transports rather than SocketCAN — so the CAN bring-up below does not carry over. See the B601-DM quick start.

When to use

• Bringing up a new B601-RS arm on an AGX Orin (JetPack 6 / L4T R36.x).
• Wiring is Orin J30 (40-pin) → SN65HVD230 → arm CAN, no USB-CAN adapter.
• Debugging "motors don't show up on CAN" on a Jetson.

Environment assumptions

• AGX Orin devkit, JetPack 6 (verified on L4T R36.5.2, 5.15.199-tegra, aarch64).
• uv on PATH; this directory's pyproject.toml pins motorbridge ≥ 0.5.
• sudo needs a TTY — an agent's non-interactive shell cannot enter a password. For any sudo step, have the user run it with the ! prefix in their terminal.

Assets (in this directory)

• assets/set_can_pinmux.py — route the header pins to the CAN controller via /dev/mem (idempotent). Required on every boot.
• assets/can0-rebot.service — systemd oneshot to bring up can0 @ 1 Mbit on boot.
• start-gateway.sh — launch the motorbridge WS gateway for Studio.

Hardware wiring (confirm before software)

Pin 1 is at the top right of J30 — the numbering runs right to left.

Orin J30 → SN65HVD230 (Waveshare labels are host-side → straight-through, not crossed):

3.3 V is on pins 1 and 17 only; grounds are on 6, 9, 14, 20, 25, 30, 34, 39. Some board revisions silkscreen CTX/CRX rather than TX/RX.

SN65HVD230 → arm: CANH→CAN_H, CANL→CAN_L. Termination target ~60 Ω across CANH–CANL (bus off). A second arm needs only a second transceiver on the can1 pins; every command below then uses can1 in place of can0.

Motor power: the arm needs its own ~24–48 V motor supply. RobStride motors run their CAN off this rail — no motor power ⇒ no CAN replies at all.

Procedure

Step 1 — Environment

cd examples/rebot
uv sync
uv run motorbridge-cli --help

Step 2 — Bring up built-in can0 (replaces the guide's PCAN-driver step)

Run via ! (needs sudo). The pinmux comes first — the header pins are not routed to the CAN controller out of the box, and the registers are cleared on every reboot:

sudo ./assets/set_can_pinmux.py     # want: pinmux set: SUCCESS
sudo modprobe can can_raw mttcan
sudo ip link set can0 type can bitrate 1000000 restart-ms 100
sudo ip link set up can0
ip -details link show can0     # want: state UP, can state ERROR-ACTIVE, bitrate 1000000

Step 3 — Verify

sudo apt install can-utils   # JetPack ships without it; candump/cansend themselves need no root

# Controller self-test — INTERNAL loopback; proves driver only, NOT pins/transceiver/wiring:
sudo ip link set can0 down
sudo ip link set can0 type can bitrate 1000000 loopback on && sudo ip link set can0 up
( timeout 2 candump -n 1 can0 & ); sleep 0.4; cansend can0 123#DEADBEEF   # expect echo
sudo ip link set can0 down
sudo ip link set can0 type can bitrate 1000000 loopback off restart-ms 100 && sudo ip link set can0 up

# Real scan (motors MUST be powered):
uv run motorbridge-cli scan --vendor robstride --channel can0 --start-id 1 --end-id 7
# want: scan done: 7 motor(s) found

Keep --end-id 7 here. A dead ID costs 80 ms + a 120 ms param-read fallback, and the range is swept once per host-id candidate (five by default), so --end-id 127 takes ~2 minutes of silence and looks hung.

Step 4 — Persist across reboots

Neither the pinmux nor the ip link bring-up survives a reboot. The unit redoes both, running the script by absolute path, so install the script first:

# Not optional: the unit runs this script by absolute path.
sudo install -D -m 755 assets/set_can_pinmux.py /opt/rebot/set_can_pinmux.py
sudo cp assets/can0-rebot.service /etc/systemd/system/
sudo systemctl daemon-reload && sudo systemctl enable --now can0-rebot.service
systemctl --no-pager status can0-rebot.service       # want: active (exited)

Step 5 — Motor IDs (1–7)

Pre-assembled arm (Studio shows 7/7 online) already has IDs 1–7 → skip to Step 6. Otherwise, one motor on the bus at a time:

uv run motorbridge-cli scan   --vendor robstride --channel can0 --start-id 1 --end-id 127
uv run motorbridge-cli id-set --vendor robstride --channel can0 --motor-id <current> --new-id <target>

The wide range is deliberate here — an unassigned motor's ID is unknown, so it has to be swept. Expect ~2 minutes with no output; it is not hung. Do not narrow it just because the verification scan in Step 3 uses --end-id 7.

id-set may report store_parameters failed (timeout) — the ID still writes; re-scan to confirm. Only use motorbridge-cli subcommands from the guide; others may spin the motors.

Step 6 — Zero calibration

./start-gateway.sh                                                    # 127.0.0.1:9002, no token
MOTORBRIDGE_WS_TOKEN=<token> BIND=0.0.0.0:9002 ./start-gateway.sh     # reachable off-box

Gateway exclusively owns the bus (stop it before any motorbridge-cli). Open Motorbridge Studio (https://motorbridge.github.io/motorbridge-studio/), confirm 7/7 online, pose the arm at home, set current position as zero for all 7 joints, verify ~0.

Studio is a browser app, so the loopback default reaches it only from a browser on the Orin. Bind wider and the gateway demands a token; a browser cannot set WebSocket request headers, so pass it in the URL: ws://<orin-ip>:9002/?motorbridge_ws_token=<token>.

Troubleshooting tree

Golden rule: on a single-node CAN bus, "nothing replies" almost always means no other powered node is ACKing. Check motor power FIRST, before any software/pinmux work.

Multimeter quick-checks: CANH–CANL (bus off) ~60 Ω good / ~120 Ω one terminator / open = broken / ~0 short-or-swap · arm power connector ~24–48 V (0 V ⇒ e-stop/fuse/loose plug) · transceiver 3V3→GND ~3.3 V.

CAN0 pinmux registers (AGX Orin AON block): can0_dout = 0x0c303010 → 0xc400; can0_din = 0x0c303018 → 0xc458.