The robot has a compass module, which it uses to find its direction. This sketch will make sure the robot goes towards a certain direction.

When you hold the robot in your hands and rotate, you will the screen change, indicating direction.

NB : magnets will interfere with the compass. If you're getting unexpected results, check to make sure there are none around.

Hardware Required

  • Arduino Robot


  1. Upload the example, unplug USB and turn on power.
  2. Place the robot on the ground.
  3. After the starting screen, a graph will appear on-screen, representing the compass
  4. The robot will start moving in a direction (in this example, it will sart heading south). If you move it in a different direction, it will turn back to the way it wants to move.
  5. If you want to change the robot's heading, in the code, look for int direc=180 at the beginning of the code. Change this value to another number, between 0 and 359. 0 represents north, 90 is east, 180 is south, and 270 is west. Where do you want to go?

Try it out

Check how the compass works


/* Robot Compass

 The robot has an on-board compass module, with
 which it can tell the direction the robot is
 facing. This sketch will make sure the robot
 goes towards a certain direction.

 Beware, magnets will interfere with the compass

 * Arduino Robot

 created 1 May 2013
 by X. Yang
 modified 12 May 2013
 by D. Cuartielles

 This example is in the public domain

// include the robot library
#include <ArduinoRobot.h>
#include <Wire.h>

int speedLeft;
int speedRight;
int compassValue;
int direc = 180;  //Direction the robot is heading

void setup() {
  // initialize the modules

void loop() {
  // read the compass orientation
  compassValue = Robot.compassRead();

  // how many degrees are we off
  int diff = compassValue - direc;

  // modify degress
  if (diff > 180) {
    diff = -360 + diff;
  } else if (diff < -180) {
    diff = 360 + diff;

  // Make the robot turn to its proper orientation
  diff = map(diff, -180, 180, -255, 255);

  if (diff > 0) {
    // keep the right wheel spinning,
    // change the speed of the left wheel
    speedLeft = 255 - diff;
    speedRight = 255;
  } else {
    // keep the right left spinning,
    // change the speed of the left wheel
    speedLeft = 255;
    speedRight = 255 + diff;
  // write out to the motors
  Robot.motorsWrite(speedLeft, speedRight);

  // draw the orientation on the screen

See Also