added arduino, modified build

arduino/libraries/Robot_Control/examples/explore/R04_Compass/R04_Compass.ino

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+/* 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
+ readings.
+
+ Circuit:
+ * 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
+  Robot.begin();
+  Robot.beginTFT();
+  Robot.beginSD();
+  Robot.displayLogos();
+}
+
+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
+  Robot.drawCompass(compassValue);
+}