I have some problems with the Arduino DUE.
When cut the PowerSupply off, the RTC of the Cortex-M3 still should run. For this there es is Backup-Battery at the VDDBU-Pin at the Atmel.
But everytime i program, reset, or cut off the Power Supply the RTC is empty.
How can i fix this?
I hope I could fix it, when I set the Arduino into backup mode, so the RTC could going on with the Battery Supply, but it drains aroud 200µA. (The Datasheet says it should it should drain around 2,5A in Backup Mode)
SCB->SCR |= (uint32_t) SCB_SCR_SLEEPDEEP_Msk; __WFE();
Or are there other ways to safe the RTC time?