diff --git a/firmware/main.c b/firmware/main.c
index 5e1e087..b36759b 100644
--- a/firmware/main.c
+++ b/firmware/main.c
@@ -32,7 +32,9 @@
 /* variables */
 volatile uint8_t state_portD; // the state of port D
 volatile bool scale_on = false; // is the scale on (based on the SCALE_ON PIN)
+#ifdef DEBUG
 volatile bool scale_old = false; // the previous state (to detect changes)
+#endif
 volatile bool pwm_high = false; // is the PWM for the weight measurement high
 volatile bool measurement_flag = false; // is a PWM  measurement value ready
 volatile uint16_t measurement_value = 0; // the PWM measurement value from the timer
@@ -146,25 +148,33 @@ int main(void)
 
 	printf(PSTR("welcome to the body scale weight reader\n")); // print welcome message
 	while (true) { // endless loop for micro-controller
+#ifdef DEBUG
 		/* display if scale switches on */
 		if (scale_old!=scale_on && scale_on) {
 			printf(PSTR("scale start\n"));
 			scale_old=scale_on;
 		}
+#endif
 		/* display value if available */
 		if (measurement_flag) {
 			if (pwm_high) {
+#ifdef DEBUG
 				printf("high: %u\n",measurement_value);
+#endif
 			} else {
+#ifdef DEBUG
 				printf("low: %u\n",measurement_value);
+#endif
 			}
 			measurement_flag = false;
 		}
+#ifdef DEBUG
 		/* display if scale switches off */
 		if (scale_old!=scale_on && !scale_on) {
 			printf(PSTR("scale stop\n"));
 			scale_old=scale_on;
 		}
+#endif
 		/* go to sleep and wait for next interrupt */
 		set_sleep_mode(SLEEP_MODE_IDLE);
 		sleep_mode();