Joystick-Control

Joystick Control

Prerequisites

Create 4 motors (left_back, left_front, right_back, right_front) and the controller named Controller1.

Note: you'll have to reverse one of the sides of the chassis!

set_tank()

We want independent control over the left and right side of the drive. We can create a set_tank function that has two input parameters, one for the left side and one for the right.

// Set voltage
const int SCALE = 120;
void set_tank(int left, int right) {
  left_front.spin(fwd, left*SCALE, voltageUnits::mV);
  left_back.spin(fwd, left*SCALE, voltageUnits::mV);
  right_front.spin(fwd, right*SCALE, voltageUnits::mV);
  right_back.spin(fwd, right*SCALE, voltageUnits::mV);
}

User Control

We could just use set_tank(Controller1.Axis3.value(), Controller2.Axis2.value()); and call it a day, but the joysticks don't always come back perfectly to 0. When this happens, the motors move very slowly forward when you want them to stop. We can fix this with a programmed dead zone.

Using if statements, we can check when the absolute value of the joystick is less then 5. When it is, we set left_joy or right_joy to 0 so the motors wouldn't move.

void usercontrol(void) {
  // User control code here, inside the loop
  while (true) {
    // This is the main execution loop for the user control program.
    // Each time through the loop your program should update motor + servo
    // values based on feedback from the joysticks.

    // ........................................................................
    // Insert user code here. This is where you use the joystick values to
    // update your motors, etc.
    // ........................................................................

    // Variables for the left and right joystick
    int left_joy = Controller1.Axis3.value();
    int right_joy = Controller1.Axis2.value();

    //
    // Joysticks don't always come back to 0 perfectly, so a programmed threshold makes driving easier.
    //

    // If the absolute value of left joy is less then 5...
    if (abs(left_joy) < 5) {
      left_joy = 0; // Set left_joy to 0
    }

    // If the absolute value of right joy is less then 5...
    if (abs(right_joy) < 5) {
      right_joy = 0; // Set right_joy to 0
    }
    
    // Set the drive to left joy and right joy
    set_tank(left_joy, right_joy);

    wait(20, msec); // Sleep the task for a short amount of time to
                    // prevent wasted resources.
  }
}