// name the pins
int ledPin = D6;

// create a variable to store the
// current brightness of the LED
int ledValue = 0;
void setup()
{
   //Register our Particle function to allow
   // Control of the LED
   Particle.function("led", ledControl);

   // Make the variable 'ledValue' available through
   // the Particle cloud as 'brightness'
   Particle.variable("brightness", ledValue);

   // Set up pin for output
   pinMode(ledPin, OUTPUT);

}
void loop()
{
   // Nothing to do here
}

int ledControl(String command)
{
    // Convert the passed variable to an integer
   ledValue = command.toInt();

   // Check it is a valid number
   if( ledValue > 255 ) return -1;
   if( ledValue < 0 ) return -1;

   // Use PWM to set the brightness
   // of the LED
   analogWrite(ledPin, ledValue);

   // Return 1 to say completed successfully
   return 1;
}