#include <Wire.h>

#define LED D4

void setup() {

  pinMode(LED, OUTPUT);

  Serial.begin(9600); /* begin serial for debug */
  Wire.begin(D1, D2); /* join i2c bus with SDA=D1 and SCL=D2 of NodeMCU */
}

void loop() {
  Wire.beginTransmission(8); /* begin with device address 8 */
  Wire.write("Hello Arduino");  /* sends hello string */
  digitalWrite(LED, HIGH);

  Wire.endTransmission();    /* stop transmitting */

  Wire.requestFrom(8, 13); /* request & read data of size 13 from slave */
  while (Wire.available()) {
    char c = Wire.read();
    Serial.print(c);
  }
  Serial.println();
  delay(1000);
            digitalWrite(LED, LOW);

}