serial not working after waking up

Hi all,

I am doing a project that makes a LoRa sender to send data periodically and stays at sleep mode at the most time.

Now the problem is that serial monitor didn't display anything after the board waking up from sleep. I thought the reason is that When the board goes into sleep, the serial is also turned off.

However, when the board wakes up, the serial doesn't wake up too. It needs to be re-open in the loop function. The thing is, after I added the code of opening the serial, I need to close the serial monitor manually and re-open that after the board wake up to make the programme keep running the rest code after Serial.begin();, which is obviously not ideal.

Does anyone know how to solve this problem?

Many thanks!

How are you putting the board to sleep?

using rtc zero library

the code is rtc.standby();

I know it's a different library, but I suspect the information in this thread is still relevant: