/**
   Arduino Keypad Manual
*/

#include <LiquidCrystal.h>
#include <Keypad.h>

/* Display */
LiquidCrystal lcd(12, 11, 10, 9, 8, 7);

/* Keypad setup */
#define KEYPAD_ROWS 4
#define KEYPAD_COLS 4
byte rowPins[KEYPAD_ROWS] = {5, 4, 3, 2};
byte colPins[KEYPAD_COLS] = {A3, A2, A1, A0};
char keys[KEYPAD_ROWS][KEYPAD_COLS] = {
  {'1', '2', '3', '+'},
  {'4', '5', '6', '-'},
  {'7', '8', '9', '*'},
  {'.', '0', '$', '/'}
};

void setup() {
  lcd.begin(16, 2);
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print ("Keypad Test");

  for (int i = 0; i < KEYPAD_ROWS; i++)
  {
    pinMode (rowPins[i], OUTPUT);
    digitalWrite(rowPins[i], HIGH);
  }

  for (int i = 0; i< KEYPAD_COLS; i++)
  {
    pinMode (colPins[i], INPUT_PULLUP);
  }
}

char getKey ()
{
  for (int i = 0; i < KEYPAD_ROWS; i++)
  {
    digitalWrite(rowPins[i], LOW);
    for (int j = 0; j < KEYPAD_COLS; j++)
    {
      if (digitalRead(colPins[j])== LOW)
      {
        digitalWrite(rowPins[i], HIGH);
        return keys [i][j];
      }
    }
    digitalWrite(rowPins[i], HIGH);
  }
  return 0;
}

void loop() {
  char key = getKey();
  if (key)
  {
    lcd.setCursor(0, 1);
    lcd.print (key);
  }
}