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

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64

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

const int pulsePin = A0;
int sensorValue = 0; 
int bpm = 0;        
unsigned long lastBeatTime = 0;
int threshold = 500; 

void setup() {
  // Initialize Serial Monitor
  Serial.begin(9600);

  // Initialize OLED display
  if (!display.begin(SSD1306_I2C_ADDRESS, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    for (;;);
  }
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 0);
  display.println(F("Heartbeat Monitor"));
  display.display();
  delay(2000);
}

void loop() {
  sensorValue = analogRead(pulsePin);
  if (sensorValue > threshold) {
    unsigned long currentTime = millis();
    bpm = 60000 / (currentTime - lastBeatTime); 
    lastBeatTime = currentTime;
    display.clearDisplay();
    display.setCursor(0, 0);
    display.println(F("Heartbeat Monitor"));
    display.setCursor(0, 20);
    display.print(F("BPM: "));
    display.print(bpm);
    display.display();
    Serial.print("BPM: ");
    Serial.println(bpm);
  }

  delay(100); // Sampling delay
}