instrument-a-day 2017, day 18: lobster bowl

lobsterbowl.ino

// Lobster Bowl arduino due touch glitch thing

// readCapacitivePin
// Arduino Due version, from http://playground.arduino.cc/Code/CapacitiveSensor
//  Input: Arduino pin number
//  Output: A number, from 0 to 17 expressing
//  how much capacitance is on the pin
//  When you touch the pin, or whatever you have
//  attached to it, the number will get higher
uint8_t readCapacitivePin(int pinToMeasure) {
  pinMode(pinToMeasure, OUTPUT);
  digitalWrite(pinToMeasure, LOW);
  delay(1);
  // Prevent the timer IRQ from disturbing our measurement
  noInterrupts();
  // Make the pin an input with the internal pull-up on
  pinMode(pinToMeasure, INPUT_PULLUP);
  // Now see how long the pin to get pulled up. This manual unrolling of the loop
  // decreases the number of hardware cycles between each read of the pin,
  // thus increasing sensitivity.
  uint8_t cycles = 17;
       if (digitalRead(pinToMeasure)) { cycles =  0;}
  else if (digitalRead(pinToMeasure)) { cycles =  1;}
  else if (digitalRead(pinToMeasure)) { cycles =  2;}
  else if (digitalRead(pinToMeasure)) { cycles =  3;}
  else if (digitalRead(pinToMeasure)) { cycles =  4;}
  else if (digitalRead(pinToMeasure)) { cycles =  5;}
  else if (digitalRead(pinToMeasure)) { cycles =  6;}
  else if (digitalRead(pinToMeasure)) { cycles =  7;}
  else if (digitalRead(pinToMeasure)) { cycles =  8;}
  else if (digitalRead(pinToMeasure)) { cycles =  9;}
  else if (digitalRead(pinToMeasure)) { cycles = 10;}
  else if (digitalRead(pinToMeasure)) { cycles = 11;}
  else if (digitalRead(pinToMeasure)) { cycles = 12;}
  else if (digitalRead(pinToMeasure)) { cycles = 13;}
  else if (digitalRead(pinToMeasure)) { cycles = 14;}
  else if (digitalRead(pinToMeasure)) { cycles = 15;}
  else if (digitalRead(pinToMeasure)) { cycles = 16;}

  // End of timing-critical section
  interrupts();

  // Discharge the pin again by setting it low and output
  //  It's important to leave the pins low if you want to 
  //  be able to touch more than 1 sensor at a time - if
  //  the sensor is left pulled high, when you touch
  //  two sensors, your body will transfer the charge between
  //  sensors.
  digitalWrite(pinToMeasure, LOW);
  pinMode(pinToMeasure, OUTPUT);

  // set back to input mode 
  pinMode(pinToMeasure, INPUT);
  
  return cycles;

}

void setup() {
  // speaker on pin 13
  pinMode(13, OUTPUT);
}

bool o;

void loop() {
  for (int i=22; i<=53; i+=1) {
    int t = readCapacitivePin(i);
    if (t>1) {
      delayMicroseconds(t*(53-i)*10);
      o = !o;        
      digitalWrite(13, o);
    }
  }
}