Why PA15 o/p pin of STM32L432KB have 1V signal upon MCU RESET?

[Maunik Patel]

In my project, PA15 pin is configured as o/p pin and is responsible to control BG96 module connected with the MCU.

When I load program in controller and open debugging session, SDO shows 1V signal on PA15 (i.e. when controller is RESET).

When PA15 is SET, its voltage level is 3.2V and when it is RESET, its voltage level is 0V.

Can anyone guide me how to set PA15's voltage to 0V when MCU is RESET ?

This situation is mandatory in my project at it can misguide my BG96 module.

Thank You,

Maunik Patel

[waclawek.jan · Accepted solution]

PA15 is one of the debug pins and reset sets it as AF0 (JTDI) and sets its internal pull-up - see General-purpose I/O (GPIO) sub-chapter of the GPIO chapter in RM0394. Thus you should add an external pull-down.

JW

[Tesla DeLorean]

Add code in your Reset Handler to reconfigure the pin.

Or as Jan suggests put a more aggressive pull-down on the pin, try 1K

[Maunik Patel]

Thank you @Community member​ and @Community member​ for your answers.

The information given by you is helpful for me.

Thank You...