FreeRTOS with STM32 and going into STOP mode

[aggarg (Gaurav Aggarwal)]

@bremenpl

• I run the FreeRTOS application normally.
• I decide to go to STOP mode, so I call the right HAL API function.
• The MCU is in STOP mode, all peripherals are off.
• I wake up the MCU via one of the supported WKUP pins,
• The MCU resets and everything as if it was caused by the #RESET line, apart from that one bit in the registers that allow you to check that it was actually a WKUP action (PWR_FLAG_SB).

I am not familiar with the STOP mode exactly but from the FreeRTOS prescriptive, you are essentially stopping everything and then doing a reset which will start everything fresh, right? If so, it should work - just remember to mask all other interrupts including the tick interrupt so that the MCU does not wake up unnecessarily.

@bremenpl

What was beneficial for the application at the time was to go to STOP mode with RTC and RAM retention. So in practice the Scheduler would go to sleep after entering the right code part in one of the threads and then wake up in the exact same position without loosing any context. The timers and peripherals should be off at the time.

This should be achievable with tickless idle.