Unable to Use Pin PC15 as GPIO_Input or GPIO_Output

[krushna_moukthik]

Hello Community,

I’m facing an issue with Pin PC15 on my board. I am unable to configure or use it as a GPIO, either as input or output. I’ve tried basic initialization, but it doesn’t seem to respond as expected.

Has anyone experienced a similar issue with PC15, or is there a special configuration/limitation I should be aware of? Any guidance or suggestions would be greatly appreciated.

Thank you in advance!

Clock Configuration:

LSI at 32 KHz

HCLK at 86 MHz

[AScha.3]

Hi,

PC15 , from ds :

+

So these pins are on backup domain ;  you have it working ? (Vbat supply ? )

+ read RTC description...or set it in Cube .

[Jojo_ · Accepted solution]

Hello,

Are you using a nucleo board ?

if so, please check the board user manual for info on how to configure the solder bridges to use PC15 as normal GPIO, since by default this pin is used to provide LSE clock.

Section "6.5.2 LSE clock (low-speed external clock) – 32.768 kH" should have the info you need:

https://www.st.com/resource/en/user_manual/um2505-stm32g4-nucleo64-boards-mb1367-stmicroelectronics.pdf

[krushna_moukthik]

Hi @Jojo_ 

Yes, I was indeed working with a Nucleo board. The issue has been resolved after changing the solder bridges as per the user manual. Specifically, modifying the solder bridge settings allowed PC15 to function as a general-purpose GPIO instead of being dedicated to the LSE clock.