     scheduler.timer(MEASURE, MEASURE_PERIOD);
     #if DEBUG
         Serial.println(" no ack!");
-        delay(2);
+        serialFlush();
     #endif
 }
 

void loop () {
    #if DEBUG
        Serial.print('.');
        delay(2);
    #endif

    #if PIR_PORT

            #if DEBUG
                Serial.print(" ack ");
                Serial.println((int) i);
                serialFlush();
            #endif
            // reset scheduling to start a fresh measurement cycle
            scheduler.timer(MEASURE, MEASURE_PERIOD);
