PB6 not working when debugging

[DavidNaviaux]

I am using PB6 as a GPIO input with a pull-up for monitoring a switch to ground.  It works properly when not debugging but has some kind of signal on it when debugging that prevents proper operation.  Note: I am using the STLINK-V3SET debugger.

Is there a way that I can disable whatever is causing this?

[Tesla DeLorean]

Check pin configuration and involvement with UCPD and pull down. Check Data Sheet. No specific involvement with debugger unless it changes RCC or GPIO registers.

[DavidNaviaux]

Thank you Tesla, 

I'm not sure what you mean.  I am using USB in the project; could it be related to this?  I notice that one of the PB6 pin options is the USART1_TX pin.  I see in a design from ST that that signal (from PA9) is connected to the 14-pin JTAG connector pin 14.  Is it possible that the STM32G474RB3 uses this pin while debugging? 

[waclawek.jan · Accepted solution]

Tesla meant this.

JW

[DavidNaviaux]

Thanks again waclawek.jan.  I'll do some more research.

[DavidNaviaux]

I was able to solve the PB6 issue by forcing PA9 and PA10 to be initialized as low outputs or by setting the UCPD1_DBDIS bit in the PWR_CR3 register.  The explanation is in footnote 6 of pin definition table (Table 12) in the STM32G474xB datasheet (page 72).  I appreciate all of your help and that of the other contributors on this forum.