Thanks,
I started with integers but I'll need to compare them with MQTT message payloads which are (from memory) char *. When I used integers, I had a Switch Case to take action depending on which detected state but I couldn't find a way to convert the payload to an int, even though it's a single integer character. I don't mind either way, so long as I can get compatible types to assign and test
A pointer to some zero to hero well drafted docs on type management would be good. Searching has returned too many snarky comments or 'not quite what I'm after' on Stack Overflow and the like
Cheers
This is different from what you currently have... which is a pointer to a char array (char array because you use double quotes). So "0" is actually 2 bytes, because is includes a string terminator (0x00).
In this case, FANSTATE should be declared as const char *, because it points to a constant. This does not make FANSTATE itself constant, that would be declared as const char * const FANSTATE.
I declare FANSTATE as a char but not a constant and assign one of the above consts to it:
char FANSTATE = FANHUM;
I try to assign one of the other consts to it:
char FANSTATE = FANTIMED;
And get a whole heap of errors, including the first,. which complains about redefinition of 'char FANSTATE'. Which looks wrong, if I've removed const from FANSTATE.
Sounds like you are putting "char" before FANSTATE every time you use it, which is attempting to create a new variable each time. You only declare a variable once, from then on just use "FANSTATE = FANTIMED", not "char FANSTATE = FANTIMED".
Seemingly not. I wasn't aware. I've removed that test and it now compiles and I can publish to MQTT_SUB_LIGHT_STATE and the ESP8266 now receives the message on that topic and I can print and otherwise use the topic and the payload message. Thanks all!
I'll try and post the completed code, when I've finished adding the state control features
I also subscribe to a message whose payload I successfully extract in my callback function
void mqttCallback(char *topic, byte *payload, unsigned int length) {
Serial.print ("Message arrived on Topic: ");
Serial.println(topic);
char message[5]={0x00}; //initialise blank (0x00) message as a char array of four characters with one extra for the compiler to append a terminating null char
for(int i=0;i<length;i++){ // I added the moustaches. Fairly sure they were excluded in error
message[i]=(char)payload[i]; //loop over the payload array and load each character into the message array
//Serial.println(message[i]);
}
message[length]=0x00; //reset the message length or set the content of the message array to null??
//Serial.println(message);
String str_msg = String(message); //cast the message as a string
//Serial.println(str_msg);
// //NodeRed telling ESP8266 what the fanState should be - to set the LEDs and set the fanState variable to match
if(topic == MQTT_SUB_LIGHT_STATE){
if(strcmp(message,FANHUM)){ //set green LED on
Serial.print(message);
}
else if(str_msg == FANTIMED){ //set green LED to flash on/off every 2 secs until done
Serial.print(message);
}
else if(str_msg == FANONMAX){ //set green LED to flash on/off three times then stay off for ten secs and repeat until done
Serial.print(message);
}
else if(str_msg == FANOFF){ //set red LED to flash on for 1 sec every 10 sec
Serial.print(message);
}
}
}
But now the compiler reports errors converting char (ie str_msg) to const char * (eg FANTIMED) for each of the IF statements.
Now I'm confused because I removed the * from the consts at the top and I'd have thought comparing a char with a const char would be trivial.
