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Tutorial 01: Scan and Identify Motors

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Prerequisites

  • motorbridge installed
  • CAN interface configured and up
  • Motors powered on

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Why Scan First?

Scanning is essential because it:
  1. Confirms wiring - Verifies physical connections are correct
  2. Validates bitrate - Ensures CAN baud rate matches motor settings
  3. Discovers IDs - Finds motor_id and feedback_id pairs needed for control
  4. Detects conflicts - Identifies duplicate IDs that could cause communication issues

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Quick Scan with CLI

The fastest way to discover motors: 
# Scan all vendors on can0
motorbridge-cli scan --vendor all --channel can0 --start-id 1 --end-id 255

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Expected Output

command=scan vendor=all transport=auto channel=can0 model=4340 id_range=[0x1,0xFF] timeout_ms=80

[scan:damiao] channel=can0 model=4340 id_range=[0x1,0x20] timeout_ms=80
[hit] vendor=damiao probe=0x01 esc_id=0x1 mst_id=0x11
[hit] vendor=damiao probe=0x02 esc_id=0x2 mst_id=0x12
[.. ] vendor=damiao probe=0x03 no reply

[scan:myactuator] channel=can0 model=X8 id_range=[0x1,0x20] timeout_ms=80
[hit] probe=0x01 vendor=myactuator feedback_id=0x241 temp=32.5C vel=+0.000rad/s angle=+0.125rad

scan done: 3 motor(s) found
  probe=0x01 vendor=damiao esc_id=0x1 mst_id=0x11
  probe=0x02 vendor=damiao esc_id=0x2 mst_id=0x12
  probe=0x01 vendor=myactuator feedback_id=0x241 temp=32.5C vel=+0.000rad/s angle=+0.125rad

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Vendor-Specific Scanning

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Damiao Motors

motorbridge-cli scan \
    --vendor damiao \
    --channel can0 \
    --start-id 0x01 \
    --end-id 0x20 \
    --feedback-base 0x10
How it works:
  • Probes each motor_id from start to end
  • Calculates feedback_id = feedback_base + (motor_id & 0x0F)
  • Reads ESC_ID (rid=8) and MST_ID (rid=7) to confirm identity

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RobStride Motors

motorbridge-cli scan \
    --vendor robstride \
    --channel can0 \
    --start-id 1 \
    --end-id 127 \
    --feedback-ids 0xFF,0xFE,0x00,0xAA
How it works:
  • RobStride uses different feedback IDs
  • Tries multiple feedback_ids per motor_id
  • Uses ping command and parameter read as probes

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MyActuator Motors

motorbridge-cli scan \
    --vendor myactuator \
    --channel can0 \
    --start-id 1 \
    --end-id 32
How it works:
  • MyActuator uses feedback_id = 0x240 + motor_id
  • Requests feedback and waits for response
  • Limited to IDs 1-32

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HighTorque Motors

motorbridge-cli scan \
    --vendor hightorque \
    --channel can0 \
    --start-id 1 \
    --end-id 127

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Scanning via Serial Bridge

For Damiao motors using USB-CAN adapter: 
motorbridge-cli scan \
    --vendor damiao \
    --transport dm-serial \
    --serial-port /dev/ttyACM0 \
    --serial-baud 921600 \
    --start-id 1 \
    --end-id 32

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Programmatic Scanning

You can also scan from Python: 
import time
from motorbridge import Controller

def scan_damiao(channel: str, start_id: int, end_id: int) -> list[dict]:
    """Scan for Damiao motors and return list of discovered motors."""
    found = []

    for motor_id in range(start_id, end_id + 1):
        # Calculate expected feedback_id
        feedback_id = 0x10 + (motor_id & 0x0F)

        ctrl = Controller(channel)
        try:
            motor = ctrl.add_damiao_motor(motor_id, feedback_id, "4340P")
            try:
                # Try to read ESC_ID register
                esc_id = motor.get_register_u32(8, timeout_ms=100)
                mst_id = motor.get_register_u32(7, timeout_ms=100)

                found.append({
                    "motor_id": motor_id,
                    "feedback_id": feedback_id,
                    "esc_id": esc_id,
                    "mst_id": mst_id
                })
                print(f"[hit] motor_id=0x{motor_id:02X} esc=0x{esc_id:X} mst=0x{mst_id:X}")

            except Exception:
                print(f"[.. ] motor_id=0x{motor_id:02X} no reply")
            finally:
                motor.close()
        except Exception as e:
            print(f"[err] motor_id=0x{motor_id:02X} {e}")
        finally:
            ctrl.close_bus()
            ctrl.close()

    return found

# Run scan
motors = scan_damiao("can0", 1, 20)
print(f"\nFound {len(motors)} motor(s)")
for m in motors:
    print(f"  motor_id=0x{m['motor_id']:02X} feedback_id=0x{m['feedback_id']:02X}")

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Understanding Scan Results

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Damiao Format

[hit] vendor=damiao probe=0x01 esc_id=0x1 mst_id=0x11
FieldMeaningUse in add_damiao_motor()
probeCAN ID probed—
esc_idMotor ID register valuemotor_id parameter
mst_idFeedback ID register valuefeedback_id parameter

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MyActuator Format

[hit] probe=0x01 vendor=myactuator feedback_id=0x241 temp=32.5C vel=+0.000rad/s angle=+0.125rad
FieldMeaning
probeMotor ID (1-32)
feedback_idExpected feedback CAN ID
tempMOSFET temperature
velCurrent velocity
angleCurrent position

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RobStride Format

[hit] probe=0x7F vendor=robstride via=ping feedback_id=0xFE device_id=127 responder_id=254
FieldMeaning
probeDevice ID probed
viaDiscovery method (ping or read-param)
feedback_idFeedback ID that worked
device_idDevice ID from ping response
responder_idResponder ID from ping response

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Troubleshooting

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No Motors Found

  1. Check CAN interface 
    ip link show can0
# Should show "UP" state
  2. Check wiring
    • CAN_H and CAN_L connected correctly
    • Termination resistors (120Ω) at bus ends
    • Motor powered on
  3. Check bitrate 
    # Motor and CAN interface must match
sudo ip link set can0 type can bitrate 1000000
  4. Try wider ID range 
    motorbridge-cli scan --vendor all --start-id 0 --end-id 255

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Timeout Errors

Increase scan timeout: 
motorbridge-cli scan --vendor damiao --timeout-ms 200

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Multiple Motors Same ID

If scan shows multiple motors with same ID: 
# Power on motors one at a time
# Use id-set to change IDs
motorbridge-cli id-set --motor-id 0x01 --new-motor-id 0x02 --store 1

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Recording Motor Configuration

After scanning, record the discovered configuration: 
# motors.py - Generated from scan
MOTOR_CONFIG = {
    "front_left_hip": {
        "vendor": "damiao",
        "model": "4340P",
        "motor_id": 0x01,
        "feedback_id": 0x11,
    },
    "front_left_knee": {
        "vendor": "damiao",
        "model": "4340P",
        "motor_id": 0x02,
        "feedback_id": 0x12,
    },
    # ... more motors
}

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Next Steps