Power on reset (PORRST) not detected on STM32L471RGT6

[rwils.1]

Hi,

I am trying to detect whether a reset event was caused by power on rather than any other reset such as a button reset or a software reset. I attempted to use

 if (__HAL_RCC_GET_FLAG(RCC_FLAG_PORRST) != RESET)

but the compiler reports that PORRST is not recognized. I tried BORRST and that is recognized but i don't believe that that setting is solely for power on detection.

Thanks in advance

Richard

[waclawek.jan]

Try using normal register access and symbols from the CMSIS-mandated device header.

JW

[rwils.1]

Thank you Jan, I'm not sure not sure where to find that device header.

Regards

Richard

[waclawek.jan]

Hi Richard,

I meant https://raw.githubusercontent.com/STMicroelectronics/STM32CubeL4/master/Drivers/CMSIS/Device/ST/STM32L4xx/Include/stm32l471xx.h and you have it under a similar path at your computer...

...but I spoke too soon: unlike some other STM32, the 'L4xx appears to have no PORRST flag in RCC_CSR:

Maybe POR is indicated by absence of any other flags being set in that register, but that needs some testing.

JW

[rwils.1]

Thank you Jan, much appreciated.

[Piranha]

Maybe read the reference manual?

The device has an integrated power-on reset (POR) / power-down reset (PDR), coupled with a brown-out reset (BOR) circuitry. The BOR is active in all power modes except Shutdown mode, and cannot be disabled.

During power-on, the BOR keeps the device under reset until the supply voltage VDD reaches the specified VBORx threshold.

Therefore at least for these devices POR=BOR and it sets BORRSTF. And in addition the PINRSTF will always be set.

[rwils.1]

Thanks!