How to config dtb and kernel for usb otg in colibri imx6

Technical Support
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1

Hi,
Can any one help me with how to config dtb and kernel to work properly with usb otg in colibri imx6, please?
Can I select between host and peripheral mode without reboot?
I read the manual and it says that in colibri imx6 it is not “true otg”. what is that suppose to mean?

thanks

2

The USB OTG mode is enabled by default in the latest Colibri iMX6 device tree: with this line: dr_mode = "otg";

It is true that our Colibri iMX6 does not fully/properly implement OTG protocol. However, it is capable of selecting between host & device mode based on the state of the USB VBUS_DETECT (USBC_DET). This is described in the Colibri Design Guide and Colibri iMX6 datasheet.

3

Thanks,

From Colibri Design Guid I realized that host and device needs two different circuit(pages 15 and 16). Is this the reason why I can not have device and host at the same time?

4

If by “at the same time” you mean concurrently, no, of course, one can only ever use any USB interface either as a device or host port at any one time. However, all our carrier boards do support switching between device and host functionality at runtime based on USBC_DET as @brandon.tx mentioned above. So please check the schematics of e.g. our Colibri Evaluation board for a suitable circuit to allow automatic switching.

5

Thanks,
I’m sorry for ambiguity. I mean Can I switch between host and client with one circuit and at the runtime without reboot? I am still confused what is that suppose to mean by “is not true otg”?

6

“Not true OTG” in this cases means two things. First true OTG actually uses two signals being ID and VBUS to support 3 different states: not connected aka suspended, device and host. Secondly, full OTG also supports advanced use-cases where both peers may be OTG capable meaning they would negotiate e.g. which one would now act in which role which is also not supported in the Colibri case. I hope this answers your confusion.