#include <Wire.h>
int status=0;
void serial_printing_fn(int bytes){
  String m="";
  while (Wire.available()){
    char c=Wire.read();
    m+=c;
  }
  Serial.print("Command from master:")
  Serial.println(m);
  status=1;
}
void request_calback_fn(){
  if(status==0):{
    Wire.write("not completed");
  }
  else{
    Wire.write("completed");
  }
}
void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");
  Wire.begin(21,22,0x08);
  Wire.onReceive(serial_printing_fn);
  Wire.onRequest(request_callback_fn):
}

void loop() {
  
}