Axis#

Introduction #

The axis class is a derived class of the controller class. It provides access to controller joystick axis values and joystick axis change callbacks.

An axis object is accessed through a controller object. It is not constructed directly.

The front side of the EXP Controller with the joystick axis numbers highlighted in red. On the surface of the controller, the left joystick is labeled as Axis 4 for left and right movement and Axis 3 for up and down movement, while the right joystick is labeled as Axis 1 for left and right movement and Axis 2 for up and down movement.

Access #

The controller class provides the following axis objects. Each object is an instance of the axis class.

Axis Object	Example Usage	Description
`Axis1`	`Controller.Axis1.position()`	Right joystick horizontal axis.
`Axis2`	`Controller.Axis2.position()`	Right joystick vertical axis.
`Axis3`	`Controller.Axis3.position()`	Left joystick vertical axis.
`Axis4`	`Controller.Axis4.position()`	Left joystick horizontal axis.

Notes #

Before using an axis member function, create a controller object.
position returns a value from -100 to 100.

// Create a controller object
controller Controller = controller();

Member Functions #

The axis class includes the following member functions:

Getter — Read joystick axis position.

position — Returns the position of the joystick axis.

Callback — Run a function when the joystick’s position changes along an axis.

changed — Runs a function when the joystick’s position changes along that axis.

Getter #

position #

position returns the position of the joystick axis as a value from -100 to 100.

Available Function

int32_t position(percentUnits units = percentUnits::pct) const;

Parameter	Type	Description
`units`	`percentUnits`	Optional. The unit used for the returned axis value. The default is `percentUnits::pct`.

Return Value

Returns an int32_t value from -100 to 100.

100 — The joystick axis is fully moved in the positive direction.
0 — The joystick axis is centered.
-100 — The joystick axis is fully moved in the negative direction.

Example

// Turn with the left joystick
while (true) {
  if (Controller.Axis4.position() > 10) {
    Drivetrain.turn(right);
  }
  else if (Controller.Axis4.position() < -10) {
    Drivetrain.turn(left);
  }
  else {
    Drivetrain.stop();
  }

  wait(20, msec);
}

Callback #

changed #

changed runs a function when the joystick’s position changes along that axis.

Available Function

void changed(void (* callback)(void)) const;

Parameter	Type	Description
`callback`	`void (*)(void)`	A function to run each time the joystick’s position changes along that axis.

Return Value

This function does not return a value.

Example

Define the callback function outside of main.

// Rumble when the left joystick moves
void controllerRumble() {
  Controller.rumble(".");
}

int main() {
  vexcodeInit();

  // Run controllerRumble when the joystick's position changes along Axis4
  Controller.Axis4.changed(controllerRumble);
}