​

let lowFrequencies = [697, 770, 852, 941]; // Low-frequency group

let highFrequencies = [1209, 1336, 1477, 1633]; // High-frequency group

let osc1, osc2; // Two oscillators for the dual tones

​

function setup() {

  createCanvas(400, 400);

  textSize(20);

  textAlign(CENTER, CENTER);

​

  // Initialize oscillators

  osc1 = new p5.Oscillator('sine');

  osc2 = new p5.Oscillator('sine');

​

  // Set initial volume to 0 (muted)

  osc1.amp(0);

  osc2.amp(0);

​

  // Start the oscillators

  osc1.start();

  osc2.start();

}

​

function draw() {

  background(220);

  text("Press 0-9, *, or # to play a DTMF tone", width / 2, height / 2);

}

​

// Play DTMF tones when keys are pressed

function keyPressed() {

  let row, col;

​

  // Map keypad characters to row and column indices

  switch (key) {

    case '1': row = 0; col = 0; break;

    case '2': row = 0; col = 1; break;

    case '3': row = 0; col = 2; break;

    case 'A': row = 0; col = 3; break;

    case '4': row = 1; col = 0; break;

    case '5': row = 1; col = 1; break;

    case '6': row = 1; col = 2; break;

    case 'B': row = 1; col = 3; break;

    case '7': row = 2; col = 0; break;

    case '8': row = 2; col = 1; break;

    case '9': row = 2; col = 2; break;

    case 'C': row = 2; col = 3; break;

    case '*': row = 3; col = 0; break;

    case '0': row = 3; col = 1; break;

    case '#': row = 3; col = 2; break;

    case 'D': row = 3; col = 3; break;

    default: return; // Exit if an unrecognized key is pressed

  }

​

  // Set oscillator frequencies

  let lowFreq = lowFrequencies[row];

  let highFreq = highFrequencies[col];

  osc1.freq(lowFreq);

  osc2.freq(highFreq);

​

  // Gradually increase amplitude

  osc1.amp(0.5, 0.05); // Smooth fade-in over 0.05 seconds

  osc2.amp(0.5, 0.05);

}

​

function keyReleased() {

  // Gradually decrease amplitude when key is released

  osc1.amp(0, 0.05); // Smooth fade-out over 0.05 seconds

  osc2.amp(0, 0.05);

}