UnoBlynkHeartRate.ino

/*
  Project: Display Heart Rate Data on IoT Blynk Using Arduino (Maker UNO)
  Board: Arduino Uno (Maker UNO)
  
  Connections:
  Maker UNO | Finger-clip Heart Rate
         5V - VCC
        GND - GND
        SDA - SDA
        SCL - SCL
  
  External libraries:
  - Blynk by Volodymyr Shymanskyy V0.6.1 (Manager)
  - BlynkESP8266 by Volodymyr Shymanskyy (Zip)
    https://github.com/vshymanskyy/BlynkESP8266
 */

#define BLYNK_PRINT Serial

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

// 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);

long prevMillis = 0;
int interval = 1000;
char bpm;

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

  EspSerial.println("AT+RST");
  delay(1000);
  while (EspSerial.available()) {
    EspSerial.read();
  }

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

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

  Serial.println("heart rate sensor:");
  Wire.begin();
}

void loop()
{
  Blynk.run();

  if (millis() - prevMillis > interval) {

    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.virtualWrite(0, bpm);
    
    prevMillis = millis();
  }
}