int ledPin = D2;

void setup() {
    
    pinMode( ledPin, OUTPUT );
    digitalWrite( ledPin, LOW );
    //LED is initially turned off.
    
    Particle.function( "led", ledControl );
    //register function
    
}

int ledControl( String command ) {
    
    int state = LOW;
    
    if( command == "CALL" ) {
        
        for ( int i = 0; i < 3; i++ ) {
        
        digitalWrite( ledPin, HIGH );
        delay( 500 );
        digitalWrite(ledPin, LOW );
        delay( 500 );
        }
    }    
    
    else if( command == "HIGH" ) {
        state = HIGH;
    } else if( command == "LOW" ) {
        state = LOW;
    } else {
        return -1;
    }
    
    digitalWrite( ledPin, state );
    return 1;
}



void loop() {
    
}