/*
 * Ping
 * ====
 * Adapted from a program by Dave Chen and Simen Svale Skogsrud
 * 
 * This program assumes that the light sensor is on IN_2 and
 * that it points in the same direction as the infrared connection
 * on the robot. It beeps when the robot gets close to an obstacle.
 * This is done by repeatedly sending IR messages. These cause a
 * large fluctuation in light intensity.
 * 
 * This is a nice mechanism to find a close by wall without bumping
 * in to it.
 */

#define THRESHOLD 200    // Making this larger decreases the distance

int lastlevel;

task Ping()
// Constantly test whether there is a high fluctuation 
{
  SetSensor(SENSOR_2,_SENSOR_CFG(SENSOR_TYPE_LIGHT, SENSOR_MODE_RAW));
  lastlevel = 0;
  while(true)
  {
    SendMessage(0);
    if(lastlevel > SENSOR_2)
    {
      // Close to something
      PlaySound(1);
      Wait(30);
    }
    lastlevel = SENSOR_2;
    lastlevel -= THRESHOLD;
  }
}

task main()
{
  start Ping;
}