In the steps below, we explain how to assemble our flagship robot, the SO-101.
## Source the parts
Follow this [README](https://github.com/TheRobotStudio/SO-ARM100). It contains the bill of materials, with a link to source the parts, as well as the instructions to 3D print the parts.
And advise if it's your first time printing or if you don't own a 3D printer.
## Install LeRobot 🤗
To install LeRobot, follow our [Installation Guide](./installation)
In addition to these instructions, you need to install the Feetech SDK:
```bash
pip install -e ".[feetech]"
```
## Step-by-Step Assembly Instructions
The follower arm uses 6x STS3215 motors with 1/345 gearing. The leader, however, uses three differently geared motors to make sure it can both sustain its own weight and it can be moved without requiring much force. Which motor is needed for which joint is shown in the table below.
| Leader-Arm Axis | Motor | Gear Ratio |
| ------------------- | :---: | :--------: |
| Base / Shoulder Pan | 1 | 1 / 191 |
| Shoulder Lift | 2 | 1 / 345 |
| Elbow Flex | 3 | 1 / 191 |
| Wrist Flex | 4 | 1 / 147 |
| Wrist Roll | 5 | 1 / 147 |
| Gripper | 6 | 1 / 147 |
## Configure the motors
### 1. Find the USB ports associated with each arm
To find the port for each bus servo adapter, connect MotorBus to your computer via USB and power. Run the following script and disconnect the MotorBus when prompted:
Remove the USB cable from your MotorsBus and press Enter when done.
[...Disconnect corresponding leader or follower arm and press Enter...]
The port of this MotorsBus is /dev/tty.usbmodem575E0032081
Reconnect the USB cable.
```
Where the found port is: `/dev/tty.usbmodem575E0032081` corresponding to your leader or follower arm.
</hfoption>
<hfoption id="Linux">
On Linux, you might need to give access to the USB ports by running:
```bash
sudo chmod 666 /dev/ttyACM0
sudo chmod 666 /dev/ttyACM1
```
Example output:
```
Finding all available ports for the MotorBus.
['/dev/ttyACM0', '/dev/ttyACM1']
Remove the usb cable from your MotorsBus and press Enter when done.
[...Disconnect corresponding leader or follower arm and press Enter...]
The port of this MotorsBus is /dev/ttyACM1
Reconnect the USB cable.
```
Where the found port is: `/dev/ttyACM1` corresponding to your leader or follower arm.
</hfoption>
</hfoptions>
### 2. Set the motors ids and baudrates
Each motor is identified by a unique id on the bus. When brand new, motors usually come with a default id of `1`. For the communication to work properly between the motors and the controller, we first need to set a unique, different id to each motor. Additionally, the speed at which data is transmitted on the bus is determined by the baudrate. In order to talk to each other, the controller and all the motors need to be configured with the same baudrate.
To that end, we first need to connect to each motor individually with the controller in order to set these. Since we will write these parameters in the non-volatile section of the motors' internal memory (EEPROM), we'll only need to do this once.
If you are repurposing motors from another robot, you will probably also need to perform this step as the ids and baudrate likely won't match.
The video below shows the sequence of steps for setting the motor ids.
Connect the usb cable from your computer and the power supply to the follower arm's controller board. Then, run the following command or run the API example with the port you got from the previous step. You'll also need to give your leader arm a name with the `id` parameter.
Connect the controller board to the 'gripper' motor only and press enter.
```
As instructed, plug the gripper's motor. Make sure it's the only motor connected to the board, and that the motor itself is not yet daisy-chained to any other motor. As you press `[Enter]`, the script will automatically set the id and baudrate for that motor.
<details>
<summary>Troubleshooting</summary>
If you get an error at that point, check your cables and make sure they are plugged in properly:
<ul>
<li>Power supply</li>
<li>USB cable between your computer and the controller board</li>
<li>The 3-pin cable from the controller board to the motor</li>
</ul>
If you are using a Waveshare controller board, make sure that the two jumpers are set on the `B` channel (USB).
</details>
You should then see the following message:
```bash
'gripper' motor id set to 6
```
Followed by the next instruction:
```bash
Connect the controller board to the 'wrist_roll' motor only and press enter.
```
You can disconnect the 3-pin cable from the controller board, but you can leave it connected to the gripper motor on the other end, as it will already be in the right place. Now, plug in another 3-pin cable to the wrist roll motor and connect it to the controller board. As with the previous motor, make sure it is the only motor connected to the board and that the motor itself isn't connected to any other one.
Repeat the operation for each motor as instructed.
> [!TIP]
> Check your cabling at each step before pressing Enter. For instance, the power supply cable might disconnect as you manipulate the board.
When you are done, the script will simply finish, at which point the motors are ready to be used. You can now plug the 3-pin cable from each motor to the next one, and the cable from the first motor (the 'shoulder pan' with id=1) to the controller board, which can now be attached to the base of the arm.
Next, you'll need to calibrate your robot to ensure that the leader and follower arms have the same position values when they are in the same physical position.
The calibration process is very important because it allows a neural network trained on one robot to work on another.
#### Follower
Run the following command or API example to calibrate the follower arm:
The video below shows how to perform the calibration. First you need to move the robot to the position where all joints are in the middle of their ranges. Then after pressing enter you have to move each joint through its full range of motion.
Congrats 🎉, your robot is all set to learn a task on its own. Start training it by following this tutorial: [Getting started with real-world robots](./il_robots)
