Using BLE to control multiple LEDs

Projects General Guidance
1

Hi everyone,

I am pretty new to BLE (and coding for that matter), and was looking at the project in the link below.

https://learn.sparkfun.com/tutorials/sik-experiment-guide-for-the-arduino-101genuino-101-board/experiment-21-using-the-on-board-bluetooth-low-energy-ble

I was able to get this working, but I was curious how the code would need to change if I wanted to control more than one LED. My first instinct would be to send different values for each LED to the arduino and use if statements to distinguish which LED I was looking to change and which pin to address, but I didn't know if you were able to send values other than 0 or 1 to the board. If someone could explain how I can go about doing this, that would be great.

Thanks

2

Serial comms tutorial

3

There are a couple of ways to do this.
1 - create additional characteristics for the additional LEDs.
2 - use a single characteristic and use codes for the additional LEDS.

  1. Each LED would have its own characteristic and the on/off value would be 0/1 for all LEDs.
    Each addition characteristic needs to use a unique UUID so LED #2 would be 19B10002-E8F2-537E-4F6C-D104768A1214 and LED 3 would be 19B10003-E8F2-537E-4F6C-D104768A1214

Each char needs to have a unique reference, like
BLEUnsignedCharCharacteristic switch1Characteristic("19B10001-E8F2-537E-4F6C-D104768A1214", BLERead | BLEWrite);
BLEUnsignedCharCharacteristic switch2Characteristic("19B10002-E8F2-537E-4F6C-D104768A1214", BLERead | BLEWrite);
BLEUnsignedCharCharacteristic switch3Characteristic("19B10003-E8F2-537E-4F6C-D104768A1214", BLERead | BLEWrite);

You then have checks for each switch characteristic.

#2 is probably the easiest but maybe not inline with the intentions of BLE.
Just use additional values for the other LEDs; 0/1 for LED1, 2/3 for LED 2 and 4/5 for LED3

you then extend the following section

if (switchCharacteristic.value()) 
{  
       digitalWrite(ledPin, HIGH);         
} 
      //else turn the LED off
else 
{                              
      digitalWrite(ledPin, LOW);   
}

to something like this (not tested):

if         (switchCharacteristic.value() == 0) {  digitalWrite(led1Pin, LOW);   } 
else if   (switchCharacteristic.value() == 1) {  digitalWrite(led1Pin, HIGH);   } 
else if   (switchCharacteristic.value() == 2) {  digitalWrite(led2Pin, LOW);   } 
else if   (switchCharacteristic.value() == 3) {  digitalWrite(led2Pin, HIGH);   } 
else if   (switchCharacteristic.value() == 4) {  digitalWrite(led3Pin, LOW);   } 
else if   (switchCharacteristic.value() == 5) {  digitalWrite(led4Pin, HIGH);   }

or a case statement