Drive a Yahboom Rover with a Gamepad

Requirements

• A Raspberry Pi 4 running an instance of viam-server. See our Raspberry Pi Setup Guide for instructions.
• A Yahboom 4WD Smart Robot
• A Bluetooth gamepad controller. For this tutorial we used an 8BitDo controller.

Configuring the Board

Go to the Viam app (app.viam.com) in a web browser, and navigate to the Config tab of the robot associated with your Raspberry Pi. To create a new component you’ll be working within the Create Component section of the Components subtab.

The first component you will add is the board which represents the Raspberry Pi to which the other components are wired. For component Type, select board. Then you can name the board whatever you like as long as you are consistent when referring to it later; local is a good name since it is the board you will communicate with directly. For Model, select pi. Click the Create Component button. You don’t need to add any attributes for this one, so your configured board will look something like this:

Configuring the Motors and Wheels

Since both right side motors of the Yahboom rover are wired together to a single motor driver, the right side motors are configured as a single motor component in the Viam config file. Later we will configure both left side motors as another motor.

As with all other components, find the Create Component box at the bottom of the Config tab. Start with the right set of wheels, and name the component right. For the Type, select motor. For the Model, select gpio. Click Create Component. Click the Board dropdown and select local since that is what this motor driver is wired to.

You will need to tell Viam how this motor is wired to the Pi. In the Component Pin Assignment section of the right motor card, toggle the Type to In1/In2 because that is the compatible mode for this motor driver. If the Yahboom setup instructions are followed correctly, the following pins should be correct: set a to 35, b to 37, and pwm (pulse-width modulation) to 33. You should leave dir pin blank, because Yahboom’s motor driver uses an a/b/pwm configuration.

Click Show more and set max_rpm to 300. You can ignore the other optional attributes.

Save the config by clicking Save Config at the bottom of the page.

Having configured these two components, you should now be able to actuate your motor. Click Control at the top of the page to navigate to the Control tab. There, you should see a panel for the right motor: you can use this panel to set the motor’s power level.

Please be careful when activating your robot! Start with the power level set to 10% and increase it incrementally (about 10% each time), activating the motor at each step until the wheels are rotating at a reasonable rate. Ensure the rover has sufficient space to drive around without hitting anyone or anything. Consider possibly holding your robot off the ground so it cannot run away or collide with anything unexpected.

At this point, the wheels on one side of your robot should be working. Now try to add the other set of wheels using the same steps and see if you can get this robot driving with all of the components working together. To do this, we’ll have to add the other motor component and link them together with a base.

To do this, go back to the Config tab and find the Create Component box. The config attributes for this motor will be very similar to the right motor, which makes sense as the hardware is the same and it is connected to the same board. The only difference will be the Name which will be left and the pins it is connected to, which should be set as follows: a (In1) to 38, b (In2) to 40, and pwm to 36.

Save the config and hop over to the control view again. You should now see two motors and be able to make each set of wheels spin.

Configuring the Base

Unite these wheel sets with a base component, which is used to describe the physical structure onto which your components are mounted. Configuring a base will also give you a nice UI for moving the rover around.

In the Create Component box, name the component yahboom-base. For the Type select base and for the Model select wheeled. Click Create Component. For Right Motors select right (the name we cleverly gave to the motor on the right side). For Left Motors select left. For width_mm, use 150, which is the approximate distance between the right and left wheels. For wheel_circumference_mm use 220.

If you click Go to Advanced you can see that the Attributes field now contains the following:

{
  "width_mm": 150,
  "wheel_circumference_mm": 220,
  "left": ["left"],
  "right": ["right"]
}

The whole base card will look something like this:

When you save the config and switch to the control view once more, you should have new buttons for the base functionality. On the Keyboard tab of the base control card you can enable keyboard control to drive the rover with the WASD keys. Also check out the Discrete tab of the base control area for a different type of control. Try playing around with these and get a sense of how the base moves.

Awesome! Now you have a rover which you can drive using a webUI. In the next step, we’ll try to make it more fun to drive around like an RC car by attaching a Bluetooth controller and using that to control the rover. If you’ve ever connected a Bluetooth device using the Linux command line, great! If not, strap in, it’s going to be a bit of a ride. If you would like to skip adding a Bluetooth controller, jump ahead to the Configuring the Camera Component section of the tutorial.

Connecting a Bluetooth Controller

Make sure the 8bitdo controller mode switch is set to S, hold down Start for a few seconds, and when the LED underneath the controller changes to green, press the pair button for 3 seconds. For more information about the controller buttons and Bluetooth modes, consult the manual included with the controller.

Run sudo bluetoothctl scan on to list all Bluetooth devices within reach of the Raspberry Pi. As you do this, in terminal make sure you are in your Pi and not in your computer. This command will scan all the devices but the 8bitdo controller will have a MAC address that begins E4:17:D8.

If you see a large log of devices, to see the addresses that only begin with E4:17:D8 you can use the grep command line tool. It is an acronym that stands for Global Regular Expression Print and allows to search for a string of characters in a specified file: sudo bluetoothctl scan on | grep "E4:17:D8"

Once you find it in the listings, pair with the controller: sudo bluetoothctl pair <8bitdo-mac-address>. Do not forget to take the < and > symbols out as you paste your address.

Then connect the controller: sudo bluetoothctl connect <8bitdo-mac-address>

Lastly trust the controller, which makes reconnecting easier in the future: sudo bluetoothctl trust <8bitdo-mac-address>

To confirm the connection, you can list connected devices with: sudo bluetoothctl devices | cut -f2 -d| while read uuid; do sudo bluetoothctl info $uuid; done|grep -e "Device\|Connected\|Name"

If you would like a stronger understanding of bluetoothctl and managing Bluetooth devices in Linux, we recommend this guide.

Now you can add this controller to the robot’s config. In the next Create Component field, name the component 8bit-do-controller. For the Type select input_controller and for the Model select gamepad. Click Create Component. Lastly, you can set the auto_reconnect attribute to true. This config adds the controller to the robot, but doesn’t give it any functionality yet.

To link the controller input to the four-wheel base functionality, you need to add our first service. Services are the software packages which provide our robots with cool and powerful functionality.

Until this point we’ve been working on the Components subtab of the Config tab, but now we’ll switch to the Services subtab. Click Services at the top of the Config tab. You will be using the Create Service card here. You can name this service yahboom_gamepad_control and give it the type base_remote_control, which is a service Viam provides for driving a rover with a gamepad. Click Create Service. You will need to configure the following attributes for this service: base should be yahboom-base and input_controller should be 8bit-do-controller:

{
  "base": "yahboom-base",
  "input_controller": "8bit-do-controller"
}

If you can not see a section where you can add the attributes, you can go to Raw JSON mode, and add this code:

  "services": [
    {
      "name": "yahboom-gamepad-control",
      "type": "base_remote_control",
      "attributes": {
        "base": "yahboom-base",
        "input_controller": "8bit-do-controller"
      }
    }
  ]

Save the config and visit the Control tab. You should have a panel for the controller which indicates whether or not it is connected. At this point moving the left analogue stick should result in movement of the rover!

Configuring the Camera Component

Before we can do that: this rover has a camera on it which we need to configure.

Once again, find the Create Component section at the bottom of the Config tab. Follow these instructions on how to connect and configure a camera. Don’t worry about calibrating the camera; it is not necessary for this tutorial. That should be enough to get the camera streaming to the webUI.

If you click on your webUI, you will be able to see your camera streaming.

Configuring the Servo Components

You may have noticed that the camera is mounted on a pair of servos which control the pan and tilt of the camera. Go to the Create Component section at the bottom of Config. Set the Name to pan, the Type to servo, the Model to pi, and click Create Component. Set Depends On to local, and pin to 23, which is the pin the servo is wired to.

Finally, add the tilt servo as well. This will be the same process as the first servo, but with the Name set to tilt and the pin to 21.

Saving the config and moving to the control UI, you should notice two new panels for adjusting these servos.

Congratulations, you have successfully configured your rover with Viam! For now, all the control is manual. If you want to go further and make your rover autonomous, you can use the Python SDK to write your own code to control it, or check out one of our other tutorials!