Sound.ino

/* 
 * Sound - Using a pressure sensor to change the tone of a piezo speaker.
 * @author Gareth Foote & Berit Greinke
 * 12th November 2015
 * 
 * Code adapted from here:
 * https://learn.adafruit.com/trinket-gemma-mini-theramin-music-maker/code
 * 
 * Note: The Arduino tone library does not work for the ATTiny85 on the
 * Trinket and Gemma.  The beep function below is similar.  The beep code
 * is adapted from Dr. Leah Buechley at
 * http://web.media.mit.edu/~leah/LilyPad/07_sound_code.html
 */

int sensorPin = 1;   // The number of the input pin for the pressure sensor
int speakerPin = 1;  // The number of the output pin for the speaker

void setup() {
  // Tell the Gemma that the speaker pin is an output
  pinMode(speakerPin, OUTPUT);
  // Tell the Gemma that the sensor pin is an input
  pinMode(sensorPin, INPUT); 
}

void loop() {
  // Read the value of the pressure sensor (variable resistor).
  // analogRead() returns a range of values.
  // The value increases the more pressure is 
  // applied to our sensor.
  int sensorReading = analogRead(sensorPin);

  // The range of values we get from our sensorReading 
  // will vary depending on the resistance of our pressure 
  // sensor. We estimate that the range is approximately 
  // between 0 and 50 depending on the pressure sensor.

  // The tone of the speaker is controlled by hertz. 
  // A sensible range is between 0hz and 2000hz. We 
  // therefore need to convert/map our sensorReading to this range.
  int frequency = map(sensorReading, 0, 50, 0, 2000);

  // We then tell the speakerPin to play a note at that
  // frequency.
  beep(speakerPin, frequency, 400);    
  
  delay(50);
}

// The function that produces the sound.
void beep (unsigned char speakerPin, int frequencyInHertz, long timeInMilliseconds) {   
  int x;   
  long delayAmount = (long)(1000000/frequencyInHertz);
  long loopTime = (long)((timeInMilliseconds*1000)/(delayAmount*2));
  for (x=0;x<loopTime;x++){  
    digitalWrite(speakerPin,HIGH);
    delayMicroseconds(delayAmount);
    digitalWrite(speakerPin,LOW);
    delayMicroseconds(delayAmount);
  }  
}