MakerUNOBlynkHeartRate.ino

/*
Project Video: https://www.youtube.com/watch?v=Dzq4tnJ0LjA

Product required:
1. Grove - Finger-clip Heart Rate Sensor
   https://www.cytron.io/p-grv-heart-finger
2. Maker UNO:
   https://www.cytron.io/p-maker-uno

Tutorial:
https://tutorial.cytron.io/2018/08/30/measuring-heart-rate-using-grove-sensor-and-arduino/
*/

/* Comment this out to disable prints and save space */
#define BLYNK_PRINT Serial

#include <ESP8266_Lib.h>
#include <BlynkSimpleShieldEsp8266.h>
#include <Wire.h>

// You should get Auth Token in the Blynk App.
// Go to the Project Settings (nut icon).
char auth[] = "YourAuthToken";

// Your WiFi credentials.
// Set password to "" for open networks.
char ssid[] = "YourNetworkName";
char pass[] = "YourPassword";

// Hardware Serial on Mega, Leonardo, Micro...
//#define EspSerial Serial1

// or Software Serial on Uno, Nano...
#include <SoftwareSerial.h>
SoftwareSerial EspSerial(2, 3); // RX, TX

// Your ESP8266 baud rate:
#define ESP8266_BAUD 9600

ESP8266 wifi(&EspSerial);

unsigned long currentMillis = 0;
unsigned long previousMillis = 0;
const int interval = 500;
unsigned char bpm = 0;

void setup()
{
  // Debug console
  Serial.begin(9600);

  delay(10);

  // Set ESP8266 baud rate
  EspSerial.begin(ESP8266_BAUD);
  delay(10);

  Wire.begin();

  Blynk.begin(auth, wifi, ssid, pass);
}

void loop()
{
  Blynk.run();

  currentMillis = millis();
  if (currentMillis - previousMillis > interval) {
    previousMillis = currentMillis;
    
    Wire.requestFrom(0xA0 >> 1, 1); // Request 1 bytes from slave device
    while (Wire.available()) { // Slave may send less than requested
      bpm = Wire.read(); // Receive heart rate value (a byte)
      Serial.println(bpm, DEC); // Print heart rate value
    }
  }
}

BLYNK_READ(V0)
{
  Blynk.virtualWrite(0, bpm);
}