3.2. I2C_Arduino_LEDcontrol.ino

#include <Wire.h>
void setup() {
Wire.begin(8);                /* join i2c bus with address 8 */
Wire.onReceive(receiveEvent); /* register receive event */
Wire.onRequest(requestEvent); /* register request event */
Serial.begin(9600);           /* start serial for debug */
pinMode(13, OUTPUT);
}
void loop() {
delay(100);
}
// function that executes whenever data is received from master
void receiveEvent(int howMany) {
while (0 <Wire.available()) {
   int c = Wire.read();      /* receive byte as a character */
   if(c == 0){
     Serial.println(c);
     digitalWrite(13, c);
   }
   if(c ==1){
     Serial.println(c);
     digitalWrite(13, c);
   }
   //Serial.print(c);           /* print the character */
 }
Serial.println();             /* to newline */
}
// function that executes whenever data is requested from master
void requestEvent() {
Wire.write("Hello NodeMCU");  /*send string on request */
}