I am making a custom board for the i.MX 8QM part and have a question about the USB interface for the UUU bootloader. Looking at the Toradex Ixora schematic it looks like the USB_ID pin is pulled low when the JP2 jumper is closed for the boot recovery mode.
If I want this USB port to only be used for periodic UUU access should I tie the USB_ID pin to ground permanently? Is this the correct usage?
From the Toradex Ixora reference design,
In order to enter recovery mode the JP2 pin needs to be ‘removed’ or in the open position. So if you tie this to ground permanently, it would be permanently in the closed position and the SoM would only be able to be in Host mode. For recovery mode we need it to be in OTG interface mode.
You can read more in the Ixora datasheet. Under 3.5 USB
Thanks for the information, one more follow up. Since we only intend on using the USB connector for the recovery mode would it make since for us to tie the ID pin on the connector to VCC then? Or should we still connect it to the corresponding pin on the iMX, USB_OTG1_ID (A37)? I see there is a pull up resistor on the USBO1_ID line (which I unfortunately truncated from the photo in the original post).
If you do not need the X9 connector as a HOST mode interface. Then I would think it would be fine to leave the design with the J2 pin in the open position (or not included), and design it as shown in the schematics.
It would still make sense to tie the ID pin to 3.3V (with resistor, as schematics show) This is an input pin and what signifies OTG or Host mode.
For a bit more information: USB_OTG1_ID is the ball name for the USBO1_ID, these are the same pin with different naming (you will see them concatenated together sometimes).