Arduino MEGA2560 wake up using DS3231 RTC I am trying to set the Arduino MEGA 2560 R3 into sleep mode and wake it up with an RTC DS3231 via interrupt. I was following this tutorial:
Tutorial

One of the libraries included is the "LowPower" library, you can find it here on GitHub. It produces the following error while compiling:

C:\XX\Arduino\libraries\Low-Power-master\LowPower.cpp: In member function 'void LowPowerClass::idle(period_t, adc_t, timer5_t, timer4_t, timer3_t, timer2_t, timer1_t, timer0_t, spi_t, usart3_t, usart2_t, usart1_t, usart0_t, twi_t)':

C:\XX\Arduino\libraries\Low-Power-master\LowPower.cpp:562:49: error: 'power_usart3_disable' was not declared in this scope

  if (usart3 == USART3_OFF) power_usart3_disable();

                                                 ^

C:\XX\Arduino\libraries\Low-Power-master\LowPower.cpp:597:48: error: 'power_usart3_enable' was not declared in this scope

  if (usart3 == USART3_OFF) power_usart3_enable();

                                                ^

exit status 1
Error while compiling for Arduino/Genuino Mega or Mega 2560.


I dont understand why there should be any functions in the library, which are not declared...This would mean noone could use it?! I am not an expert in C++ so maybe one of you could tell me what the issue could be. I am glad for any help.
after further web research, it looks like this is a bug which hasnt been fixed yet.
it was discussed previously here and here.

My solution was to go into the "LowPower.cpp" scroll down to the lines, where the functions are not declared and I just out-commented them. Compiling works now.