   // Just wake up
 }
 
+ISR(WDT_vect)
+{
+  // Wake up by watchdog
+}
+
 void setup()
 {
     watchdog_setup();

byte msgId = 0;

byte sleep_flag;

Servo servo_horz;


    // Transmit after interval
    if (now - tx_last >= tx_interval) {
        tx_last = now;
                
        // Send a transmission
        char msg[16];
        sprintf(msg, "%d,wd=%u,mv=%lu", msgId, light_level, readVcc());
