   Serial.write(result);
 }
 
-void handle_serial {
+void handle_serial() {
   if (Serial.available()) {
     int data = Serial.read();
     if (data == CMD_HEADER_A) {

    delay(500);
  }
  tray_state = TRAY_OPEN;
  KCUP_LOADER, KCUP_EJECTOR, TRAY_PISTON
  return 0;
}


// Repeated calls will do nothing
// Never returns an error, ideally
int kcup_tray_close() {
  digitalWriteFast(PIN_TRAY_PISTON, TRAY_CLOSED);
  if (tray_state != TRAY_CLOSED) {
    delay(500);
  }
