STM32WL33x default SWD pins

[angus123]

Hello all :)

I am designing a board using the STM32WL33CCV6TR, and want to program/debug using the SWD interface. However, there are multiple pins the SWDIO and SWCLK can be mapped to using alternate functions. Usually with STM products, I have seen a footnote saying which pins the SWD interface is mapped to on boot. However, I cannot see this on the STM32WL33xx datasheet.

My question is which pins should I use as SWDIO and SWCLK so that I can program the chip out of the box (without having to mess around with the bootloader). And could I have found this information, as I am sure it is somewhere but cannot find it. I am guessing the PA2 and PA3 pins, but not really for any good reason...

Many thanks in advance!

[TDK]

Look at the default GPIO register settings in the Reference Manual.

[STTwo-32 · Accepted solution]

Hello @angus123 

As Said @TDK , this information should be available on the RM0511 specially on the paragraph 7.3.1: 

During and just after reset, the alternate functions are not active and most of the 1/0 ports are configured in GPIO input pull-up mode except the SWD debug pins.

The debug pins are in AFO pull-up/pull-down after reset:

• PA2: SWDIO in pull-up
• PA3: SWDCLK in pull-down

Best Regards.

STTwo-32

[angus123]

Thank you for your help @TDK and @STTwo-32  much appriciated :)

[Charles]

@angus123 was smarter than I, I never pay attention that SWDIO and SWDCLK could be mapped elsewhere (never had issues on all STM32 I use for years) and when I designed my STM32WL3 board just saw SWDIO/SWCLK can be on PA12/PA13 so I routed to them. So I'm stuck and can't use board, I could be able to use UART and bootloader with BOOT0 but same "no luck" uart in my case is not routed to PA1/PA15

I think I'm stuck an no way to get out this error, if any option @STTwo-32 , @TDK would be appreciated, and I can give a try.

Anyway what's the use case moving away SWDIO SWDCLK on other pins than default, since doing this prevent any first flash ? 

Thanks