Internal PU/PD setting on PA8 of STM32G070RB

[FYUJI.1]

Hi,

Now, we use STM32G070RB.

Please let me make clear about internal PU/PD resistor setting on PA8.

Although we set internal PU res from GPIOA_PUPDR, measured voltage is near 0V at this port.

We found this is because the PD res that is set by SYSCFG_CFGR1[9].

After assert this bit, we could get 3.3V(pulled-up by internal res by GPIOA_PUPDR).

Actually, there is priority for these PU setting and PD setting on this port?

Br,

Yuji

[Mike_ST]

Dear Yuji,

In G070 Datasheet DS12766 (march2020), you can find the following (page 35/93):

"3. Upon reset, a pull-down resistor might be present on PA8, PD0, or PD2, depending on the voltage level on PB0,

PA9, PC6, PA10, PD1, and PD3. In order to disable this resistor, strobe the UCPDx_STROBE bit of the

SYSCFG_CFGR1 register during start-up sequence."

So I guess this is your case.

[FYUJI.1]

Dear Mike

Thanks for your answer.

Yes, I understood it.

​But, i'd like to know that whether there is priority of internal res setting.

I mean, we set PU res from GPIOA_PUPDR on PA8. Then, my expected measured voltage on this port is 3.3V(=VDD) because applied internal pull-up res.

However, actual measured voltage on this port is near 0V. This is because pull-down res that is set by UCPDx_STROBE bit of SYSCFG_CFGR1 register.

After assert this bit(=disable pull-down res), I was able to measure 3.3V on PA8.

From this, I thought there is priority for pull-up/pull-down res setting by above two register.

And, Internal resister setting by GPIOA_PUPDR and the one setting by UCPDx_STROBE bit of SYSCFG_CFGR1 can be set together, or can be set either one(exclusive)?

Br, Yuji

[waclawek.jan]

The USBC-related pulldown is not identical to the GPIO pulldown.

The USBC Rd value is nominally 5.1kOhm (strangely enough I can't ind this value in the DS - @Mike_ST​  , shouldn't this be documented there?

As the GPIO pullup is 40kOhm, having both switched ON results in value "near to 0V", without any special priority.

JW

[FYUJI.1]

Hi, JW

Thank you for your explanation.

Based on calculation with Rd 5.1k, I could get the value that is near measured value.

Do you have more information about USBC Red.

I couldn't find about it in the datasheet.

Br, Yuji

[Mike_ST]

Dear Yuji,

Please check TA0357 and AN5225, hopefully, it might help:

https://www.st.com/resource/en/technical_article/dm00496853-overview-of-usb-type-c-and-power-delivery-technologies-stmicroelectronics.pdf

https://www.st.com/resource/en/application_note/dm00536349-usb-typec-power-delivery-using-stm32xx-series-mcus-and-stm32xxx-series-mpus-stmicroelectronics.pdf

Best regards,

Mike

[FYUJI.1]

Dear Mike

Although STM32G070RB doesn't have USB function, why it has UCPD?

And, I found below table on page.38 of RM045. how is UCPD available in STM32G070RM?

And, do you have any information about below on page.167 of RM0454?

Br,

Yuji

[Mike_ST]

Dear Yuji,

Do you have an older version of the RM0454 ? It seems you have preliminary/early version.

If so, please download Rev 3 from May2020 here:

https://www.st.com/resource/en/reference_manual/dm00463896-stm32g0x0-advanced-armbased-32bit-mcus-stmicroelectronics.pdf

Table seems to have changed and 6.3.15 has been removed.

Best regards,

Mike

[FYUJI.1]

Dear Mike

I downloaded the latest version, and confirmed revision points.

But, I still don't understand why this STM32G070 has the UCPD res,and how we utilize it because this ucom doesn't have usb function.

Anyway, i understand the UCPD res is 5.1k and it is not identical to GPIO PUPUD(set by GPIOx_PUPDR).

Br, Yuji

[waclawek.jan]

Power delivery protocol is entirely separate from actual USB data transfer, using separate conductors in the cable. Actually, as of today, charging-only USBC cables (i.e. without the USB data conductors) may quite well be the prevalent type.

OTOH, 'G0 models with USB module are promised to come ever since the 'G0 line appeared (search on this forum).

JW