stm32u5 internal pull-up resistors on SDIO pins

[miladmohtashamirad]

Hi. 
Isn't it possible to turn on the internal pull-up resistors for SDIO lines in STM32U585?
In cubeMX configuration, It doesn't show pull up option in gpio config. Also choosing pull up in the init code doesn't look like enabling it. 
is there anywhere in the datasheet or reference manual that explains this?

[SofLit]

Hello, 

I don’t think it’s recommended to use internal gpio pull ups for SDIO.

To me there are two reasons: 

1- at power up the GPIOs are not yet configured and at this time the sdio pins are floating.

2- The values of the resistors.

So need to use external pull ups.

If internal pull ups was a solution it was adopted for many ST reference designs / examples.

Meanwhile to answer your remark regarding how to configure pull-up/down resistors in CubeMx on already configured pins for peripherals, you need to go to GPIO -> SDMMC and select what GPIO you need to set the internal resistor as indicated in the following screenshot:

[miladmohtashamirad]

Hi @SofLit , 
I understand that the recommendations ask for external pull-up. however for our use case we would like to see if the internal pull up on cmd line can work. 

regarding the screen shot that you shared, is it STM32U5 series? because I can't select pull-up there (my screen shot is for CMD line but that's the same for other SDIO pins as well):

Kind regards.

[SofLit · Accepted solution]

Hello,

I'm not reproducing the issue on STM32CubeMx version 6.12.1:

Are you using the latest version?

[miladmohtashamirad]

Hi. 
No. I'm using 6.11.1-RC2. 
Ok. if it's showing up in later versions of CubeMx, it proves that probably there's no hardware limit for turning pull resistors.
Thank you.