/*
 * Arduino + Sonar = Simple Theremin
 * 
 * The duration of the ping until the echo arrives to 
 * the sonar is fed directly to the DDS, thus making 
 * a direct relation between distance and frequency.
 *
 * For details on how to use the Ping))) ultrasonic sensor
 * with arduino, please check:
 * http://arduino.cc/en/Tutorial/Ping?from=Tutorial.UltrasoundSensor
 *
 * Joao Mouro (http://mouro.info)
 * 15/05/2009 
 */

int pingPin = 7;

void setup()
{
  initPWM();
  sei();
}

void loop()
{
  uint32_t duration;

  // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.
  // We give a short LOW pulse beforehand to ensure a clean HIGH pulse.
  pinMode( pingPin, OUTPUT );
  digitalWrite( pingPin, LOW );
  delayMicroseconds( 2 );
  digitalWrite( pingPin, HIGH );
  delayMicroseconds( 5 );
  digitalWrite( pingPin, LOW );

  // The same pin is used to read the signal from the PING))): a HIGH
  // pulse whose duration is the time (in microseconds) from the sending
  // of the ping to the reception of its echo off of an object.
  pinMode( pingPin, INPUT );
  
  duration = pulseIn( pingPin, HIGH );
  setFrequency( duration );

  delay(10);
}