//arduino equiv of wire.h library
#include <Wire.h>
#include <SPI.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>


#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels

#define OLED_RESET     4
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
#define I2C_ADDRESS 0x3C;
 // Reset pin # (or -1 if sharing Arduino reset pin)

// set volatile 
const char symbols[] = {"@", "!", "#", "$", "%"};

volatile boolean x = false; 


void setup() {
  // put your setup code here, to run once:
  Wire.begin();
  Serial.begin(9600);
  pinMode(2, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(2), dispSymbol, FALLING);

  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Address 0x3D for 128x64
    Serial.println(F("SSD1306 allocation failed"));
    for(;;);
  }
  delay(2000);
  display.clearDisplay();
  delay(100);
 
}

void dispSymbol(){
      Serial.println("interrupt");
      x = true;
}

void loop() {
  // put your main code here, to run repeatedly:
  if (x!= false) {
      display.clearDisplay();
      display.setTextSize(5);
      display.setTextColor(WHITE);
      display.setCursor(0, 0);
      display.println(symbols[1]);

      display.display(); 
  }



}
// now display this on LED