STM32F446 - why PB12 conflicts with USB PHY?

[Pavel A.]

Posted on March 07, 2018 at 00:16

Why CubeMX 4.24 says that PB12 conflicts with USB_OTG_HS when external HS PHY is not is use?

The MCU is F446ZCT, its USB HS core is in FS, host only mode, Activate_SOF and Activate_VBUS unchecked.

PB12 can have two alternate functions for USB HS core - but both are related only to HS mode, correct?

So why conflict with the PHY in FS internal PHY mode?

(and, by the way, what does ''Activate_VBUS'' in host mode? I use a different output pin to switch VBUS to the port).

Thanks,

-- pavel

#usb-fs #cubemx-v4.24

[Khouloud GARSI · Accepted solution]

Posted on March 07, 2018 at 18:53

Hi

pavel_a

‌,

On the datasheet, we are mentioning that the STM32F446 MCU have:

• USB 2.0 full-speed device/host/OTG controller with on-chip PHY : (OTG1_FS through GPIOA ).
• USB 2.0 high-speed/full-speed device/host/OTG controller with dedicated DMA, on-chip full-speed PHY (OTG2_FS through GPIOB) and ULPI (OTG2_HS).

If you are using the second on chip FS PHY (GPIOB), the related pins are described as HS because they are linked to the USB 2.0 high-speed/full-speed device/host/OTG controller.

On the datasheet, you may notice that the PB12 is the OTG_HS_ID in the OTG2_FS peripheral.

You may also notice that also PB14 and PB15 are mentioned as ''USB_OTG_

H

S_DM'' and ''USB_OTG_

H

S_DP''.

Thus, the if you are using the USB FS PHY through the GPIOB port, the PB12 should not be used by another peripheral.

Khouloud.

[Pavel A.]

Posted on March 07, 2018 at 22:12

Thank you,  Khouloud

-- pa

[waclawek.jan]

Posted on March 08, 2018 at 01:30

Khouloud,

in the opening post, Pavel wrote:

host only mode

What would be the function of ID pin in host-only mode?

Host only

– The force host mode bit (FHMOD) in the OTG USB configuration register(OTG_GUSBCFG) forces the OTG_FS/OTG_HS core to work as a USB host-only.In this case, the ID line is ignored even if present on the USB connector.

Jan

[Khouloud GARSI]

Posted on March 08, 2018 at 12:24

Hi Jan,

Let me check this point. I will come back to you ASAP.

Khouloud.

[Khouloud GARSI]

Posted on March 09, 2018 at 10:00

Hello,

Waclawek.Jan

‌, Ihave checked this point and you are right.

pavel_a

‌,the yellow warning on CubeMX indicates that at least one mode configuration is no longer available (Colored in red: OTG/Dual_Role_Device in your case). I apologize if my first answer was misleading. The good news is, if you're in 'Host only' mode, the PB12 pin could be used by other peripherals.

Khouloud.

[Pavel A.]

Posted on March 09, 2018 at 17:50

Thank you.

[Khouloud GARSI]

Posted on March 12, 2018 at 10:22

You're always welcome