• Easy to use.
• Use it as a 'Light Sensor' on your RCX.
• Can be used with ROBOLAB, RIS-1.0, RIS-2.0 or LejOS.
• Can be used with AMUX (Active Sensor Multiplexer)

1. Install Compass Sensor in its final position in the robot structure with all the motors, RCX and batteries in place.
2. Power ON RCX and set the Compass sensor port as Light Sensor. Do not run any program.
3. Press the calibration switch twice - this will begin calibrations and the display will increment from 1 to 100 slowly
4. Slowly turn the robot two or three times around itself in clockwise direction (taking roughly 20 seconds per turn).
5. Press the calibration switch on Compass Sensor when done.

// following program makes the rover run in a square
// beginning at heading of 72 Degrees and then turning
// 90 degrees clockwise after that.
task main()
{
    // set the port 1 to read as light
    // where the compass sensor is connected.
    SetSensor(SENSOR_1, SENSOR_LIGHT);
    SetSensorMode(SENSOR_1, SENSOR_MODE_PERCENT);
    PlaySound(SOUND_CLICK);

    while(1)
    {
        ChangeHeadingTo(20,3);  // set the direction to heading 72
        // start motors to go forward
        OnFwd(OUT_A);
        OnFwd(OUT_C);
        Wait(200);  // keep the motors running.

        // turn by 90 degrees clockwise (a change of 25)
        ChangeHeadingTo(45,3);
        // start motors to go forward
        OnFwd(OUT_A);
        OnFwd(OUT_C);
        Wait(200);  // keep the motors running.

        // turn by 90 degrees clockwise (a change of 25)
        ChangeHeadingTo(70,3);
        OnFwd(OUT_A);
        OnFwd(OUT_C);
        Wait(200);  // keep the motors running.

        // turn by 90 degrees clockwise (a change of 25)
        ChangeHeadingTo(95,3);
        // start motors to go forward
        OnFwd(OUT_A);
        OnFwd(OUT_C);
        Wait(200);  // keep the motors running.

        // stop
        Off(OUT_A);
        Off(OUT_C);
        SetPower(OUT_A+OUT_C, 8);
    }
}

void ChangeHeadingTo(int target_angle, int ERROR_MARGIN)
{
    int error;
    SetPower(OUT_A+OUT_C, 8);
    while(1)
    {
        Wait(1);
        error=target_angle-SENSOR_1 ; // get current heading error
        if (error>50)
            error=100-error;
        if (error-ERROR_MARGIN)
        {
            // turn clockwise
            OnRev(OUT_A);
            OnFwd(OUT_C);
        }

    }
}