Ultrasonic Sensor

The ultrasonic sensor proved to be difficult to set up. But with a few hacks with the help of John Legoman, it came through.

The main difficulty of the sensor is that it often fluctuates between -1 and the actual distance reading. This creates problems when our code instructs the robot to stop whenever it sees a value less than 3(stop when it's 3 inches away from a wall).

John fixed this issue by converting the sensor readings with an unsigned byte variable. This warps negatives over to the max values, and thus -1 becomes 255.
unsigned byte sonarValue
sonarValue = SensorValue[sonar]

With this conversion, the code worked beautifully.

void stopdistance(int distance);
{
  unsigned byte sonarValue
  sonarValue = SensorValue[sonar]
  while(sonarValue < distance)
   {   
      motor[motorL] = 0
      motor[motorR] = 0
   }
}

task main()
while(1==1)
{
  motor[motorL] = 80
  motor[motorR] = 75
  stopdistance(3);
}