topic Re: USB OTG in i.MX Processors

USB OTG

williamtaylor — Fri, 19 Aug 2016 20:28:08 GMT

Hi all,

I have a Wandboard quad and on its carrier board it has a USB OTG regulator that uses active low to enable USB OTG POWER.

When I plug this usb port into my laptop all is fine and the laptop recognizes the device.

On my custom board I need to use a USB OTG regulator that uses active high to enable. All other signals staying the same polarity.

Anyone have any idea which files need to be changed to accomodate this, although I am trawling to work this out, but any pointers would be really appreciated.

Thanks

Billy

Re: USB OTG

igorpadykov — Sat, 20 Aug 2016 00:10:48 GMT

Hi William

USB_ID signal is usually used as active low (when usb is host according

to usb specification) to enable USB OTG POWER.

It can not be changed by software, in general (however may depend on

particular board schematic) adding invertor is needed.

Best regards

igor

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Re: USB OTG

williamtaylor — Sat, 20 Aug 2016 13:34:13 GMT

Hi Igor, thanks very much for your fast response, I really appreciate it.

I should have made myself a bit clearer.

The USB_ID signal is not the problem.

The OTG VBUS signal is controlled by a pin from the processor, and in the case of the Wandboard connector board, it is active low(the VBUS regulator is a TI part)

On my custom connector board the OTG VBUS signal is controlled by the very same processor pin but needs to be active high(again a TI part) while all other signals maintain the same polarity.

So if I connect the OTG USB port to my PC with a non OTG cable I expect the PC to be the host, and this is the case with the Wand connector board. And I can see that the OTG regulator is turned off(the OTG VBUS SIGNAL is high)

so for my board I need this to be low.

Does that make sense?

but perhaps I am not understanding something?

Best Regards

William

Re: USB OTG

williamtaylor — Sat, 20 Aug 2016 16:17:24 GMT

please see my response Igor

Re: USB OTG

igorpadykov — Sun, 21 Aug 2016 23:23:36 GMT

Hi William

unfortunately I am not familiar with Wandboard, but if that signal is controlled by processor

gpio, seems it is possible to change its polarity in sources. Suggest to post it to

wandboard wiki so that someone familiar with that board could try to assist you.

http://wiki.wandboard.org/Main_Page

Best regards

igor

Re: USB OTG

williamtaylor — Mon, 22 Aug 2016 08:57:03 GMT

Thanks once again Igor for the fast response.

I had done that before posting here but no replies yet.

Ok, so just a thought, would I be right in saying that the sabre board

has a similar arrangement, where the USB OTG VBUS switch is controlled

from the processor?

The set up for this would be in the sources somewhere so any pointers

since I am sure it would have similarities.

I appreciate your help Igor

Best Regards

William

Re: USB OTG

williamtaylor — Thu, 25 Aug 2016 16:22:29 GMT

Hello again Igor,

I just checked and the circuit for the USB OTG on the Sabre Lite with

imx6q is more or less identical to my custom platform. Both using active

high to enable the OTG VBUS. So any pointers to the sabre sources for

setting up the usb otg pins?

thanks

William

Re: USB OTG

igorpadykov — Fri, 26 Aug 2016 05:44:44 GMT

Hi William

Sabre Lite is boundary devices board (not nxp) one can look at

https://boundarydevices.com/wp-content/uploads/2014/11/sabre_lite-revD.pdf

GitHub - boundarydevices/linux-imx6 at boundary-imx_4.1.15_1.0.0_ga

it is supported by boundary devices.

Best regards
igor

Re: USB OTG

williamtaylor — Fri, 26 Aug 2016 08:57:55 GMT

Thanks Igor, I will have a look.

USB OTG
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