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WKUP pin with internal Pull-Up

Question asked by Aaron Pica on Jul 19, 2017
Latest reply on Jul 25, 2017 by Aaron Pica

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:

  1. Configure the PA0 GPIO pin with internal Pull-Up.
  2. HAL_PWR_EnableWakeUpPin(PWR_WAKEUP_PIN1_LOW);       //Configure the WKUP line with falling edge.
  3. 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?

 

Thank you.

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