PMIC_VBUSOTG and OTG_VBUS hookup for USB Type-C

[coloradocarlos]

The OSD32MP1 has 2 pins (of many) to support USB OTG: PMIC_VBUSOTG (K8) and OTG_VBUS (K9).

The ST documentation is not clear how to use a USB Type-C connector without using a helper chip such as the STUSB1600.

Our requirement is to support the Linux USB Gadget as a Device. We have this currently working on a custom board using USBH_HS_DM2 and USBH_HS_DP2 pins without the need of the helper chip. However, a nice to have is to support a dual role and switch to Host for example a USB keyboard.

Not working yet, but also a requirement, is using the OTG Type-C as a power source when not on battery or an external power transformer. Making this interesting is that we want to support the PMIC turn-ON condition of “VBUS detection (voltage rising on VBUSOTG or SWOUT pins)”.

Are there any reference schematics on how to correctly use PMIC_VBUSOTG and OTG_VBUS that can be shared here?

[Neeraj Dantu]

Hey Carlos,

Please take a look at section 10.1.12 of the hardware getting started guide for MP1 for reference USB OTG circuit connections: https://www.st.com/resource/en/application_note/dm00389996-getting-started-with-stm32mp151-stm32mp153-and-stm32mp157-line-hardware-development-stmicroelectronics.pdf. Note the use of OTG_ID pin in addition to OTG_VBUS.

https://wiki.st.com/stm32mpu/wiki/OTG_device_tree_configuration shows the device tree configuration you will need for the OTG functionality.

Best,
Neeraj

[coloradocarlos]

I reviewed the Getting Started documentation and it appears that the OTG_ID pin is used only for USB Micro-AB connectors. In other words, it is not used for USB Type-C connectors. Same for VBUS– it can’t be used directly unless there is an intermediate circuit such as the STUSB1600 that can detect role switches. Is this correct?

[Neeraj Dantu]

Carlos,

I apologize, I did not notice the USB-C aspect of your question. Yes, I believe you are correct. For a better understanding of what is required to use a USB-C port for dual role USB2, see https://www.ti.com/lit/wp/slly017/slly017.pdf. The controller performs switching role functions and monitors VBUS.

Best,
Neeraj

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