Slave to Send Data after Receiving Command using I2C

Question

I want to have my Slave Arduino to send signal to Master after the command was made. But the Slave Arduino does not proceeds to sending the signal after doing the command. What is wrong with my code?

Slave

void receiveEvent(int bytes) {
 dir = Wire.read(); // direction
 dis = Wire.read(); // distance
 spe = Wire.read(); // speed
 eStop = Wire.read(); // 1 or 0
 Serial.println(dir);
 Serial.println(dis);
 Serial.println(spe);
 mov = true;
}
void loop() {
 Wire.onReceive(receiveEvent);
 if (dir == 1 && mov == true && eStop == false){
 motor.Distance(dis);
 motor.Speed(spe);
 motor.Forward();
 Wire.onRequest(requestEvent); 
 mov = false;
 fin = true;
 }
 if (dir == 2 && mov == true && eStop == false){
 motor.Distance(dis);
 motor.Speed(spe);
 motor.Reverse();
 Wire.onRequest(requestEvent);
 mov = false;
 fin = true; 
 }
 else{
 motor.Stop();
 }
}
void requestEvent(){
 Wire.write(1);
 fin = false;
 Serial.println("sent"); 
}

Master

#include <Wire.h>
const byte interruptPin = 2;
byte dir = 0;
byte dis;
byte spe;
bool upd;
bool state= false;
void setup() {
 Wire.begin(); 
 pinMode(interruptPin, INPUT_PULLUP);
 attachInterrupt(digitalPinToInterrupt(interruptPin), emergencyStop, CHANGE);
 Serial.begin(9600);
}
void loop() {
 if( state == false ){
 dir = 1;
 dis = 30;
 spe = 2;
 Wire.beginTransmission(9); // transmit to device #9
 Wire.write(dir);
 Wire.write(dis);
 Wire.write(spe);
 Wire.write(0); 
 Wire.endTransmission(); // stop transmitting
 state = true;
 }
 if (state == true){
 if(Wire.available() > 0){
 Wire.requestFrom(9,2); //6bytes from slave 9
 bool upd = Wire.read();
 Serial.println(upd);
 }
 } 
} 
void emergencyStop(){ // not working
 Wire.beginTransmission(9); // transmit to device #9
 Wire.write(0);
 Wire.write(0);
 Wire.write(0);
 Wire.write(1); 
 Wire.endTransmission(); // stop transmitting
}

• chrisl: Please wdit your question to include the full sketch
• Mikael Patel: Typically Wire.onReceive(callbackFunction) is called once in the setup().
• Mikael Patel: Serial print in the callback function can cause issues.

Answer 1

found my solution for this. although not verified yet, but i removed Serial print and moved the Wire.onRequest outside of the if loop. and uses a ledPin for checkups

void loop() {
 Wire.onReceive(receiveEvent);
 Wire.onRequest(requestEvent);
 if (dir == 1 && mov == true && eStop == false){
 motor.Distance(dis);
 motor.Speed(spe);
 motor.Forward();
 mov = false;
 fin = true;
 }
 if (dir == 2 && mov == true && eStop == false){
 motor.Distance(dis);
 motor.Speed(spe);
 motor.Reverse();
 mov = false;
 fin = true; 
 }
 else{
 motor.Stop();
 }
}
void requestEvent(){
 if ( fin == true){
 Wire.write(1);
 fin = false;
 digitalWrite(ledPin, HIGH);
 }
}

• Nick Gammon: Yes, you should not do serial prints inside an interrupt service routine.