Set Up Servo IDs

mix bb_so101.setup_servos PORT is an interactive wizard that assigns the six SO-101 servo IDs in turn. Use it the first time you wire up an arm, or any time you replace a servo.

Usage

mix bb_so101.setup_servos /dev/ttyUSB0
mix bb_so101.setup_servos /dev/ttyACM0 --baud-rate 500000

How it works

The wizard processes one joint at a time, in this order:

1. shoulder_pan → ID 1
2. shoulder_lift → ID 2
3. elbow_flex → ID 3
4. wrist_flex → ID 4
5. wrist_roll → ID 5
6. gripper → ID 6

For each joint the wizard:

1. Asks you to connect a single servo to the controller (disconnect all others).
2. Broadcasts a discovery query and reports the ID of whatever servo it finds.
3. Asks you to confirm, then writes the target ID to the servo's EEPROM and verifies by re-reading it back.
4. Prompts you to disconnect that servo before continuing to the next.

Once all six are programmed, daisy-chain them back together and reconnect to the controller.

Common adjustments

Servo already has the right ID

Skip it. The wizard's "skip" option leaves the servo unchanged and moves on.

One servo of a known ID

If you only need to re-program one servo (e.g. a replacement gripper servo), connect it alone, run the wizard, and skip the joints whose servos are already correct.

A custom baud rate

If you've changed the bus speed away from the 1 Mbaud default (e.g. via the Parameters panel of the dashboard), pass --baud-rate so the wizard can talk to the servo:

mix bb_so101.setup_servos /dev/ttyUSB0 --baud-rate 500000

Troubleshooting

"No servo found on the bus"

• Check that only one servo is connected — the wizard scans by broadcast, so multiple servos will all reply and confuse the discovery step.
• Confirm the serial adapter shows up as the path you passed (ls /dev/ttyUSB* or ls /dev/ttyACM*).
• Verify the servo has power and is fully wired (TX/RX swapped is the usual cause).

"ID write failed verification"

The write happens but the read-back doesn't match. Usually a flaky cable or brown-out on the power supply during the write. Retry; if it persists, the servo's EEPROM may be locked — power-cycle the bus and try again.

Next: calibrate

Once IDs are assigned, calibrate the arm so that each joint's mechanical centre maps to 0 rad.