# 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 ```bash mix bb_so101.setup_servos /dev/ttyUSB0 mix bb_so101.setup_servos /dev/ttyACM0 --baud-rate 500000 ``` | Argument | Default | Description | |------------------|----------------|----------------------------------------| | `PORT` | required | Serial port for the Feetech bus | | `--baud-rate` | `1000000` | Servo bus baud rate | | `-b` | alias | Short form of `--baud-rate` | ## 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: ```bash 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](calibrate-servos.md) so that each joint's mechanical centre maps to `0 rad`.