Sleep for 30 minutes and wakeup to make 10 LED blinks before going back to sleep again for another 30 minutes.
Note that the serial prints will not work after wakeup. Hence use a USB to UART chip to get the
Serial1 prints. This is because during sleep, the entire USB peripheral also sleeps along with the MCU, except for the RTC.
During sleep, only power indicator green LED
ON will be lighted on the RobotDyn dev board.