USB_OTG2_VBUS connection clarification for ON board chip to chip interface

[logeshs]

Hi,

We are using MCIMX7D3EVK10SD in our design.

We have received our Assembled Board. In our board USB_OTG1_DP/DN is connected to Micro USB connector. USB_OTG1_VBUS pin is left floating in processor.

Initially, We attempted to boot our board, by connecting USB cable from Test PC to device, but the device is not detected. But later we connected VBUS of connector and USB_OTG1_VBUS and device got detected and we are able to get prompt now.

But, We are using USB_OTG2_ DP and USB_OTG2_DN for on board chip to chip interface between IMX7D and LTE chip. In this port USB_OTG2_VBUS is left floating and not connected to VBUS pin of LTE. (But VBUS of LTE is supplied with onboard 5V.) For communication between IMX7D and LTE,

1. Does USB_OTG2_VBUS need to be powered for proper communication?

2. We did not Fan out USB_OTG2_VBUS in layout (floating). Do we have any internal register option to power up the USB_OTG2_VBUS pin?

3. Do we need to connect both VBUS of LTE and USB_OTG2_VBUS of IMX7D for proper communication?

Earlier as per suggestion from community VBUS of LTE pin is not connected in USB_OTG2_VBUS of processor for on board chip to chip interface.

Kindly request you to provide the solution as soon as possible.

Thanks & Regards,

Logesh

[igorpadykov]

Hi Logesh

>1. Does USB_OTG2_VBUS need to be powered for proper communication?

vbus should be connected according to usb specifications, if you are using standard software

most probably this signal is used. However in theory and depending on application one can develop

i.MX7 software (usb driver) which does not use this signal.

>2. We did not Fan out USB_OTG2_VBUS in layout (floating). Do we have any internal register option to power up >the USB_OTG2_VBUS pin?

there is no such option.

>3. Do we need to connect both VBUS of LTE and USB_OTG2_VBUS of IMX7D for proper communication?

yes according to usb specifications. If you are using standard usb driver most probably it is used for proper

operation. In theory it is possible (depending on application) to develop driver without usage of that signal.

Best regards
igor
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