 
     // limit data rate
     if(delta >= DELAY_SLOW) {
+        // switch to precise reference (2.56V)
+        analogReference(INTERNAL);
+
         // analog inputs (battery)
         raw_bat0 = analogRead(A0);      // J4 (pin 1)
         raw_bat0 = analogRead(A0);      // J4 (pin 1)


        // send indicators report
        report_indicators();


        // send timestamp

    // }

    // switch to precise reference (2.56V)
    //analogReference(INTERNAL);

    // switch to default reference (5V on Arduino Uno/Leonardo)
    analogReference(DEFAULT);

    // Arduino Leonardo has some difficulties entering in bootloarder upload mode
    // if it is sending data to serial in loop() preventing firmware update without
