Serial.print als Debug-Funktion

#define DEBUG

// DEBUG Output nur bei "aktivem" DEBUG
#ifdef DEBUG
#define DEBUG_PRINT(x) Serial.print(x)
#define DEBUG_PRINTLN(x) Serial.println(x)
#else
#define DEBUG_PRINT(x)
#define DEBUG_PRINTLN(x)
#endif

void setup() {
  Serial.begin(9600);
}

void loop() {
     DEBUG_PRINT("test 123");
     delay(1000);
}