door_post.c

int relayPin = D7;                 // choose the pin for the LED

int openCall(String extra) {
    digitalWrite(relayPin, LOW);
    delay(1500);
    digitalWrite(relayPin, HIGH);
    Particle.publish("house_door_open"); // Slack web hook to open the door
    return 1;
}

void setup()
{
  Particle.function( "open", openCall );
  
  delay(5000);                      // Allow board to settle
  Blynk.begin(auth);                // Blynk auth
  pinMode(relayPin, OUTPUT);        // Set relay as output
  digitalWrite(relayPin, HIGH);     // Initialize relay pin as HIGH
}

void loop()
{
  
}