I'm working with the STM32F769, and I want to configure the pin PA0 to wake up the MCU from Standby. The problem is that the board needs a Pull-Up in the pin to be able to detect the pulsation.
The sequence that I follow to enable the WKUP line is:
- Configure the PA0 GPIO pin with internal Pull-Up.
- HAL_PWR_EnableWakeUpPin(PWR_WAKEUP_PIN1_LOW); //Configure the WKUP line with falling edge.
- PWR->CR2 |= PWR_CR2_CWUPF1; //Clear the interruption flag (it's automatically set)
In the moment WakeUpPin is enabled, the Pull-Up disappears (the pin level goes down) even though the PUPDR is still configured.
I haven't found any reference about this behaviour in the Datasheet/Erratasheet/Reference manual. Is it limitation of the device? Is there a workaround? Am I missing something?