#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <Keypad.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

const byte ROWS = 4;
const byte COLS = 4;
char keys[ROWS][COLS] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};

byte rowPins[ROWS] = {19, 18, 5, 17}; // conecta a las filas del teclado
byte colPins[COLS] = {16, 4, 2, 15};  // conecta a las columnas del teclado

Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

String buffer = "";

void setup() {
  Serial.begin(115200);
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("Fallo pantalla OLED"));
    for(;;);
  }
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0,0);
  display.println("Iniciando...");
  display.display();
  delay(1000);
  display.clearDisplay();
}

void loop() {
  char key = keypad.getKey();
  if (key) {
    Serial.println(key);
    if (key == '#') {
      buffer = "";
      display.clearDisplay();
    } else {
      buffer += key;
      display.clearDisplay();
      display.setCursor(0, 0);
      display.println(buffer);
    }
    display.display();
  }
}