I am trying to test the low power modes on the STM32L031 Nucleo board.
I used the example of STM32Cube_FW_L0_V1.9.0 (STM32L031K6-Nucleo32\STM32Cube_FW_L0_V1.9.0\Projects\STM32L031K6-Nucleo\Examples\PWR\PWR_STOP) iwth IAR compiler.
Actually, le code works when the board is powered by le USB cable or the Vin pin.
But if the board is powered by the 5V pin or 3V3 pin, the code does not work.
The expected behavior is : wake up from STOP mode by a falling edge on PA.12, then blinking the led on PB.3 and return to STOP mode.
The PA.12 is configured with the pull up internal resistor.
The voltage on pin PA.12 shall be 3V3 due to the pull up resistor. It is the right when the board is powered by USB or Vin but the voltage on PA.12 drops around 0V when the board is powered by 5V or 3V3 pin.
Anybody has an explanation of the trouble ?