goapi
Posts: 3
Joined: Wed Feb 27, 2019 8:01 am

USB-OTG Problems

Wed Mar 06, 2019 5:49 pm

Hi,

we are trying to connect to the Raspi CM3 via USB OTG. We have two CM3s to test with. To do that we are connecting OTG-ID to 3V3 (of course we setup config.txt and cmdline.txt). For the first CM3 it used to work (not very stable, but it did work).

At some point (i could not tell, what changed tbh but we think we shorted some pins and the CM3 restarted) the OTG stopped working on this first board. When we pull OTG-ID to 3V3, it disconnects any connected USB client (for example keyboard) but the Windows PC connected to it doesn't see any client device.

OTG still works on the second CM3, BUT it's really not stable. When we restart the CM3 while it is connected, the Windows PC will see a USB client on the port but will not identify it as an ethernet connection. If we unplug and reconnect the USB connection, then the OTG connection works again.

I did notice that there doesn't seem to be all too much documentation on the compute module and specially about the OTG connection on the CM3 (most documentation we could find was about the Pi Zero). Can someone help or does anyone know what we might be missing or how to debug this problem?

Thanks in advance.

aBUGSworstnightmare
Posts: 1349
Joined: Tue Jun 30, 2015 1:35 pm

Re: USB-OTG Problems

Thu Mar 07, 2019 6:24 am

Raspberry has one USB interface only. Because of that it can either be host OR device.

Which platform do you use for your testings?

goapi
Posts: 3
Joined: Wed Feb 27, 2019 8:01 am

Re: USB-OTG Problems

Thu Mar 07, 2019 7:15 am

aBUGSworstnightmare wrote:
Thu Mar 07, 2019 6:24 am
Raspberry has one USB interface only. Because of that it can either be host OR device.

Which platform do you use for your testings?
* we know that we can only do either client or host mode
* I do not understand what kind of "platform" you mean.

aBUGSworstnightmare
Posts: 1349
Joined: Tue Jun 30, 2015 1:35 pm

Re: USB-OTG Problems

Thu Mar 07, 2019 11:47 am

Do you have a custom baseboard (risk thaf USB signal routing is not according to spec) or are you usimg the official CMIO baseboard?

goapi
Posts: 3
Joined: Wed Feb 27, 2019 8:01 am

Re: USB-OTG Problems

Thu Mar 07, 2019 11:49 am

We're using the official CMIO-Board and did exchange that to see if that might help. It doesn't..

gsh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 1416
Joined: Sat Sep 10, 2011 11:43 am

Re: USB-OTG Problems

Mon Mar 25, 2019 11:24 am

You can try using

dtoverlay=dwc2,dr_mode=peripheral

In config.txt which should force it to only work in peripheral mode. This will tell you whether it's just a detection problem or a problem with reading the OTG value.

In fact the way the OTG pin is wired isn't really correct, so I would suggest instead you remove the R12 resistor from the OTG line and instead drive it low to switch into host mode. This is actually the way it is supposed to work.
--
Gordon Hollingworth PhD
Raspberry Pi - Director of Software Engineering

javaraspi
Posts: 15
Joined: Fri Jan 25, 2019 8:32 pm

Re: USB-OTG Problems

Thu Apr 11, 2019 3:05 am

Hello goapi.

Could you make the OTG work with the solution proposed by ghs?

Thanks!

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