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``` --- ## Units The robot is built from three kinds of units (sub-assemblies) first; the legs go on the body last. There are **81 individual parts (8 kinds)** in total. | Unit | Qty | Parts inside | |---|---|---| | body_servo (body + 4 servos) | ×1 | 13 | | leg_left (left leg) | ×2 | 11 | | leg_right (right leg) | ×2 | 11 | | Part | Qty | |---|---| | Screw M3×6 | ×40 | | Screw M2×6 | ×16 | | STS3215 (case + horn: the part on the servo shaft that turns with it) | ×8 | | bracket_outline | ×4 | | leg_link1 | ×4 | | Body | ×1 | (servo-id)= ## Give each servo an ID **Before building the units, give the eight servos the IDs 1 to 8.** All eight share one bus, and the microcontroller addresses each servo by its ID. New STS3215 servos, however, **all ship as ID 1**, so out of the box they cannot be told apart. Set the IDs with **one servo connected at a time**. With two ID-1 servos on the bus, a "change ID 1 to 2" command reaches both of them and both become ID 2. The tool still sees what looks like one servo, so nothing tells you it went wrong. ### What you need - A PC (Windows / macOS / Linux) - The driver board (Waveshare Bus Servo Adapter (A)) and a USB Type-C cable - The 12 V AC adapter (item 3 in the [parts list](bom.md)) - An STS3215 (just one to start with) - Masking tape and a pen, for number labels ### Install the tool IDs are set with [feetech-cli](https://github.com/iory/feetech-cli). With the uv you installed while setting up (if you have not yet, see "Install uv" for [macOS](../getting-started/macos.md) / [Windows](../getting-started/windows.md) / [Linux](../getting-started/linux.md) first), one line installs the `feetech` command: ```console $ uv tool install feetech-cli ``` uv takes care of Python, so there is nothing else to install. The command goes into the same place as uv itself, so any shell where `uv` runs also finds `feetech`. ### Connect 1. Put **both jumpers on B (USB-SERVO)**. A is the position for driving the servos from an Arduino; left on A, the PC cannot see the servo. 2. Plug a single servo into one of the board's 3-pin connectors (D V G). 3. Plug the AC adapter into the board's DC jack. **The servo cannot be powered from USB**, so without this it does not answer. 4. Connect the board to the PC with the USB Type-C cable. ::::{grid} 1 2 2 2 :gutter: 2 :::{grid-item} ```{figure} ../_static/servo_id_setup.jpg :target: ../_static/servo_id_setup.jpg :alt: A PC, the AC adapter, the driver board and a single servo connected together The whole setup. PC to board over USB Type-C, board powered from the AC adapter, exactly one servo ``` ::: :::{grid-item} ```{figure} ../_static/servo_id_wiring.jpg :target: ../_static/servo_id_wiring.jpg :alt: The driver board with the DC jack, the USB Type-C cable and the servo cable plugged in At the board: DC jack (power) on the left, USB Type-C (PC) next to it, and the servo cable in a 3-pin connector at the top. The PWR LED lights red when power is on ``` ::: :::{grid-item} ```{figure} ../_static/servo_id_jumper.jpg :target: ../_static/servo_id_jumper.jpg :alt: Both jumpers in the B position. The board is printed with A = UART-SERVO and B = USB-SERVO Both jumpers on **B (USB-SERVO)**. What A and B mean is printed on the board ``` ::: :::: ### Number them one by one 1. Check the servo is visible. ```console $ feetech scan Found 1 servo(s) on /dev/cu.usbmodem59710813431 at 1.00Mbps: id 1 model 777 position 4095 (+179.9 deg) 12.3V 32C ``` A single `id 1` line means you are ready. The port name depends on your system (`COM3` or similar on Windows); the tool finds it by itself, so there is nothing to pass. 2. Write the new ID. It is written once you answer `y`. The first servo can keep ID 1, so this step starts with the second one. ```console $ feetech set-id 1 2 Change servo 1 to id 2? This writes the servo EEPROM. [y/N] y Servo 1 is now id 2. ``` The ID is stored in the servo's EEPROM, so it survives a power cycle. 3. Run `feetech scan` again and check the servo answers at its new ID. 4. **Label the servo.** Once they are mixed up, the only way to tell them apart is to connect them one by one again. A label on a face that stays visible after assembly also helps later, when wiring or replacing a servo. 5. Unplug it, connect the next new servo and go back to step 1. The third one gets `feetech set-id 1 3`, the fourth `feetech set-id 1 4`, and so on up to 8. ```{figure} ../_static/servo_set_id.gif :alt: feetech scan finds a servo at ID 1, feetech set-id 1 2 changes it to ID 2, and a second scan finds it at ID 2 Steps 1 to 3 on real hardware ``` ```{figure} ../_static/servo_id_label.jpg :target: ../_static/servo_id_label.jpg :width: 50% :alt: A servo with a label reading "ID:1" on its side A servo with its number label ``` ### Which servo goes where Each ID belongs to one joint of one leg. The assignment is the one in the firmware's `include/quad_calib.h` (`QUAD_SERVO_ID`), so **mount the servos exactly as shown.** A servo in the wrong place receives another joint's commands. ```{figure} assembly_img/servo_ids.png :target: assembly_img/servo_ids.png :alt: The quadruped seen from above and from the left, with each servo's ID marked. Front right 1 and 2, front left 3 and 4, rear right 5 and 6, rear left 7 and 8; the hip is odd and the knee even on every leg Servo ID assignment. Seen from above, the front (the walking direction) is the end with the tab in the middle of the body's short side ``` Use these servos when building the units below. | Unit | Servos inside | IDs to use | |---|---|---| | body_servo (body) | the hips of all four legs | 1 (front right), 3 (front left), 5 (rear right), 7 (rear left) | | leg_right (right leg) ×2 | the knees of the right legs | 2 (front right), 6 (rear right) | | leg_left (left leg) ×2 | the knees of the left legs | 4 (front left), 8 (rear left) | ### Troubleshooting | Symptom | Check | |---|---| | `feetech scan` finds nothing | The AC adapter is plugged in (PWR LED), the jumpers are on B, the servo cable is fully seated | | No port is found | The USB cable carries data (a charge-only cable shows no port) | | A servo whose bus speed was changed before is not found | `feetech scan --all-baudrates` tries every speed | | `id 2 is already used by another servo on this bus` | A servo with that ID is also connected. Leave only one and try again | ## Building the units Each kind of unit is shown once; **×N** is how many the whole robot uses. Build them from top to bottom and you will have every unit you need. In the steps, "coaxial φ◯ mm" means lining up the centres of the holes, and "mating faces" means pressing two faces flat against each other. :::{dropdown} STS3215 servo (fitting the horn) **×8** :open: Only if the horn arrived detached. If it is already fitted, skip this unit. 1. Place the **STS3215_horn** (base).  2. **STS3215_case** onto the horn — coaxial φ4.8 mm (×2), 2 mating faces.  ```{figure} ../_static/quadruped_horn_screw.jpg :target: ../_static/quadruped_horn_screw.jpg :width: 50% Hold the screwdriver tip in line with the screw hole. If the tip is at an angle the force does not get through and the screw head strips easily ``` ::: :::{dropdown} body_servo (fixing 4 servos in the body) **×1** Parts: body ×1, STS3215 ×4, M3x6 ×8 **STS3215-1 to -4** below are the CAD part numbers, not servo IDs. The four positions in the body take the hip servos (IDs 1, 3, 5, 7); match each position to its ID with the {ref}`ID assignment figure