//
// Touch Optics
// v.1
// http://touchoptics.wordpress.com
//

// Do we want debugging on serial out? 1 for yes, 0 for no
int DEBUG = 1;

const int motorPin = 9;
const int pingPin = 7;

boolean ascending = true;

void setup()
{
  pinMode(motorPin, OUTPUT);
  if (DEBUG) {
    Serial.begin(9600); // Set serial out if we want debugging
  }
}

void loop()
{
  long cm = getPingCentimeters(pingPin);
  analogWrite(motorPin,map(cm,0,200,255,0));
  delay(100);
}

long getPingCentimeters(int pin)
{
  // establish variables for duration of the ping,
  // and the distance result in inches and centimeters:
  long duration;
  // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.
  // 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);
  return microsecondsToCentimeters(pulseIn(pingPin, HIGH));
}

long microsecondsToInches(long microseconds)
{
  // According to Parallax's datasheet for the PING))), there are
  // 73.746 microseconds per inch (i.e. sound travels at 1130 feet per
  // second).  This gives the distance travelled by the ping, outbound
  // and return, so we divide by 2 to get the distance of the obstacle.
  // See: http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf
  return microseconds / 74 / 2;
}

long microsecondsToCentimeters(long microseconds)
{
  // The speed of sound is 340 m/s or 29 microseconds per centimeter.
  // The ping travels out and back, so to find the distance of the
  // object we take half of the distance travelled.
  return microseconds / 29 / 2;
}