Not able to control digital pins using commands sent via HC-05 module

Question

I am trying to control the LED on pin13 using the below code but it's not working. With this code I am able to print to the Serial Monitor but the code has no effect on the any of the digital pins. I am unable to control the LED and so I have gotten stuck and can't advance further. I can't understand why it is happening even if I have excluded the new line from the Bluetooth app that I am using to send the strings and same on the Serial Monitor.

#include<SoftwareSerial.h>          // import the serial library

SoftwareSerial bluetooth(6, 7);     // RX, TX

void setup(){
  Serial.begin(9600);               //set baud rate
  bluetooth.begin(9600);
  pinMode(13, OUTPUT);
  digitalWrite(13, LOW);
}

void loop(){
  while (bluetooth.available()){
    char ch = bluetooth.read();
    message += ch;
  }

  if(!bluetooth.available()){
    if(message != ""){
      if(message.equalsIgnoreCase("on")){
        digitalWrite(13, HIGH);
      }else{
        digitalWrite(13, LOW);
      }
      Serial.println(message);
      message = "";
    }
  }
}

Answer 1

Your logic is a complete mess. You have:

1. If a character is available, read it and add it to message.
2. If another character is available, compare what you have already stored with on.
   • If it's equal ('o' is not equal to 'on') turn on, otherwise turn off.
   • Print what you have stored.
3. Forget what you stored
4. Go to 1 (a character is still available since you never read it in stage 2).

Instead you need something more like:

1. If a character is available, read it into a variable.
2. If the character you read is a line ending character:
   • Compare your message with 'on' and take appropriate action
3. If the character you read is not a line ending character:
   • Add the character to message.
4. Go to 1.

Note how you only check once if there is a character available, and all your testing is done within that one if block.