4 X 4 MATRIX KEYPAD INTERFACE WITH ARDUINO WITHOUT LIBRARY

In this tutorial we are going to see how to interface 4 x 4 matrix keypad with Arduino.

COMPONENTS REQUIRENT

Arduino UNO

4 X 4 KEYPAD

CODE

#define r0 10
#define r1 11
#define r2 12
#define r3 13
#define c0 9
#define c1 8
#define c2 7
#define c3 6

volatile char key_value = 'x';
char key();
void keypad_init();
void setup() {
  Serial.begin(9600);
  keypad_init();
}

void loop() {
  Serial.println(key());
  delay(1000);
}

void keypad_init()
{
  pinMode(r0, OUTPUT);
  pinMode(r1, OUTPUT);
  pinMode(r2, OUTPUT);
  pinMode(r3, OUTPUT);
  pinMode(c0, INPUT_PULLUP);
  pinMode(c1, INPUT_PULLUP);
  pinMode(c2, INPUT_PULLUP);
  pinMode(c3, INPUT_PULLUP);
}

char key()
{

  digitalWrite(r0, LOW);

  digitalWrite(r1, HIGH);

  digitalWrite(r2, HIGH);

  digitalWrite(r3, HIGH);

  if (digitalRead(c0) == LOW)

    key_value = '*'; 

 while (digitalRead(c0) == LOW);

  if (digitalRead(c1) == LOW) 

   key_value = '0';

  while (digitalRead(c1) == LOW);

  if (digitalRead(c2) == LOW)

    key_value = '#';

  while (digitalRead(c2) == LOW);

  if (digitalRead(c3) == LOW)  

  key_value = 'D';  

  while (digitalRead(c3) == LOW);

  

  digitalWrite(r0, HIGH);

  digitalWrite(r1, LOW);

  digitalWrite(r2, HIGH);

  digitalWrite(r3, HIGH);

  if (digitalRead(c0) == LOW)

    key_value = '7';

  while (digitalRead(c0) == LOW);  

  if (digitalRead(c1) == LOW)

    key_value = '8';

  while (digitalRead(c1) == LOW);

  if (digitalRead(c2) == LOW)

    key_value = '9';

  while (digitalRead(c2) == LOW);

  if (digitalRead(c3) == LOW)

    key_value = 'C';

  while (digitalRead(c3) == LOW);

  

  digitalWrite(r0, HIGH);

  digitalWrite(r1, HIGH);

  digitalWrite(r2, LOW);

  digitalWrite(r3, HIGH);

  if (digitalRead(c0) == LOW)

    key_value = '4';

  while (digitalRead(c0) == LOW);

  if (digitalRead(c1) == LOW)

    key_value = '5';

  while (digitalRead(c1) == LOW);

  if (digitalRead(c2) == LOW)

    key_value = '6';

  while (digitalRead(c2) == LOW);

  if (digitalRead(c3) == LOW)

    key_value = 'B';

  while (digitalRead(c3) == LOW);

  

  digitalWrite(r0, HIGH);

  digitalWrite(r1, HIGH);

  digitalWrite(r2, HIGH);

  digitalWrite(r3, LOW);

  if (digitalRead(c0) == LOW)

    key_value = '1';

  while (digitalRead(c0) == LOW);

  if (digitalRead(c1) == LOW)

    key_value = '2';

  while (digitalRead(c1) == LOW);

  if (digitalRead(c2) == LOW)

    key_value = '3';

  while (digitalRead(c2) == LOW);

  if (digitalRead(c3) == LOW)

    key_value = 'A';

  while (digitalRead(c3) == LOW);

  return key_value;

}