int ledPin = D2;

int photoresPin = A4;
int photoresRead = 0;

void setup() {
    
    //Set the LED as Output
    pinMode(ledPin, OUTPUT);
    
   
    
    Particle.variable("photoResValue", photoresRead);
    
}

void loop() {
    
    //0-4095
    photoresRead = analogRead(photoresPin);
    
    //using map function to convert the range
    int brightness = map(photoresRead, 0 , 4095, 0, 255 );
    
    analogWrite( ledPin, brightness );
    
    delay(200);
    
 }