i.mx 8M Mini: Required USB pins to provision processor?

[adevries]

Hello,

I am working on a design that uses the i.MX 8M Mini application processor. I know this processor is capable of USB OTG mode, which uses 7 pins (VBUS, DP, DN, ID, GND, OTG_OC, and OTG_PWR). However, if I have no need for OTG mode, and I only ever need my board to act as a USB peripheral, is it acceptable to not connect pins ID, OTG_OC, and OTG_PWR? If I only route VBUS, DP, DN, and GND out to a USB connector, will I still be able to use the USB port to initially provision the processor and load the OS image on the e.MMC?

Thanks

[Yuri]

@adevries 
Hello,

  Generally - from hardware point of view - it is possible
to use Your approach, assuming the ID pin is left floating
(not grounded).

Nevertheless, regarding software, please use Chapter 19 (Porting
USB) of the i.MX Porting Guide and section 4.9 (USB)of the i.MX Linux
Reference Manual.

https://www.nxp.com/design/software/embedded-software/i-mx-software/embedded-linux-for-i-mx-applicat...

Regards,
Yuri.

[adevries]

Hi Yuri,

Thanks for the information. So when the processor is in serial download mode and writing the OS image to e.MMC, it is never acting as a USB host, right?

Do I need to change some setting in software to disable OTG functionality? Or is disconnecting OTG_OC, OTG_PWR, and ID sufficient to make sure the processor always acts as a USB peripheral?

Thanks

[Yuri · Accepted solution]

@adevries 
Hello,

  Correct - when the processor is in serial download mode and writing the OS image
to e.MMC, it is never acting as a USB host.

 When the USB ID is left floating means USB device mode. This is true as much as software
follows USB specs. 

Regards,
Yuri.

[adevries]

great, thank you for the information!