#include <Keypad.h>

const byte numRows = 4;
const byte numCols = 4;

char keymap[numRows][numCols] = {
  {'1', '2', '3', 'A'}, 
  {'4', '5', '6', 'B'}, 
  {'7', '8', '9', 'C'},
  {'*', '0', '#', 'D'}
};

byte rowPins[numRows] = {9, 8, 7, 6};
byte colPins[numCols] = {5, 4, 3, 2};
Keypad myKeypad = Keypad(makeKeymap(keymap), rowPins, colPins, numRows, numCols);

const int buzzerPin = 10;

void myTone(int pin, int frequency, int duration) {
  long period = 1000000L / frequency;
  long cycles = (long)frequency * duration / 1000;
  
  for (long i = 0; i < cycles; i++) {
    digitalWrite(pin, HIGH);
    delayMicroseconds(period / 2);
    digitalWrite(pin, LOW);
    delayMicroseconds(period / 2);
  }
}

void setup() {
  pinMode(buzzerPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  char keypressed = myKeypad.getKey();

  if (keypressed != NO_KEY) {
    Serial.println(keypressed);
    
    switch (keypressed) {
      case '1': myTone(buzzerPin, 262, 200); break; // C4
      case '2': myTone(buzzerPin, 294, 200); break; // D4
      case '3': myTone(buzzerPin, 330, 200); break; // E4
      case '4': myTone(buzzerPin, 349, 200); break; // F4
      case '5': myTone(buzzerPin, 392, 200); break; // G4
      case '6': myTone(buzzerPin, 440, 200); break; // A4
      case '7': myTone(buzzerPin, 494, 200); break; // B4
      case '8': myTone(buzzerPin, 523, 200); break; // C5
      case '9': myTone(buzzerPin, 587, 200); break; // D5
      case '0': myTone(buzzerPin, 659, 200); break; // E5
      case '*': myTone(buzzerPin, 698, 200); break; // F5
      case '#': myTone(buzzerPin, 784, 200); break; // G5
      case 'A': myTone(buzzerPin, 880, 200); break; // A5
      case 'B': myTone(buzzerPin, 988, 200); break; // B5
      case 'C': myTone(buzzerPin, 1047, 200); break; // C6
      case 'D': myTone(buzzerPin, 1175, 200); break; // D6
      default: break;
    }
  }
}