Convert MQTT message into int values

[Katoz]

I want to control an RGB ring light from my smartphone, I don't go into the details of how the system works but essentially I receive an MQTT message with hue, saturation and brightness values on my ESP8266.

To handle MQTT messages I use this function:

void callback(char* topic, byte* payload, unsigned int length)
{
  //Print message
  Serial.print("Message arrived: ");

  Serial.print(topic);
  Serial.print(", ");
  for (int i = 0; i < length; i++) {
    Serial.print((char)payload[i]);
  }

  if (strcmp(topic, "setHSV/LIGHT") == 0)
  {
      //Do something
  }
}

and when I change the color of the light from my smartphone I get a message like this on the ESP8266: setHSV/LIGHT = 0,0,59

My question is: how do I convert the 3 values I receive into 3 separate int values that I can use to control the LEDs?

Thanks for the help

[wildbill]

Look at using strtok and atoi on the payload string.

[Katoz]

It took me several hours last night but I managed to nearly solve my problem

void callback(char* topic, byte* payload, unsigned int length)
{
  //Print message
  Serial.print("Message arrived: ");
  Serial.print(topic);
  Serial.print(", ");
  for (int i = 0; i < length; i++) {
    Serial.print((char)payload[i]);
  }




  if (strcmp(topic, "setHSV/LIGHT") == 0)
  {
    char* str = (char* )payload; //conversion from a byte array to a character array
    str[length]= '\0'; 
    Serial.println("");
    Serial.print("Char array before: "); Serial.print(str);

    char* token = strtok(str, ",");

    while (token != NULL) {
      int n = atoi(token);
      Serial.println(n);
      token = strtok(NULL, ";");
    }

//    Serial.println("");
//    Serial.print("Char array after: "); Serial.print(str);


//    int n[10];
//    for (int a = 0; token != NULL; a++) {
//      n[a] = atoi(token);
//      Serial.println(n[a]);
//      token = strtok(NULL, ";");
//    }


  }

This is what I get in the serial console:

Message arrived: setHSV/LIGHT, 30,48,66
Char array before: 30,48,6630
48

Only the second value it's being printed and I can't figure why

[wildbill]

Get the first one with atoi of the payload before you use strtok. Get the others with the while loop, but fix the typo where you are looking for a semi-colon rather than a comma.

[Katoz]

I did the first conversion whit atoi outside the loop and the other two inside the loop and it worked, after fixing the typo of course.