Use CDC and NET device class together

[Wini-Buh]

In my project I'm running two different USB classes (device stack), CDC and NET. That means I can either communicate trough a serial connection (CDC class) or over a network connection via USB (RNDIS ode ECM, NET class) derived from the net_lwip_webserver example. So all is build depended, means I can only use one of the two classes in the project at build build.

My question: Is it possible to define a descriptor setting to let both classes use at the same time ?

Any help would be welcome

[hathach]

it is easily possible, what have you tried so far, and is the issue with your descriptor

[Wini-Buh]

I did not tried anything yet. I only use two separate descriptor sets, because I don't have any idea to merge the two sets together (in fact the descriptor settings are sometimes a little mystery to me). Maybe you could give me some advise how build this descriptor that fulfils my requirements ?

Here is my source file containing the descriptor settings for the two classes. The macro LWIP_ACTIV switches between the two settings.

usb_descriptors.zip

[hathach]

the problem can be the caching issue with windows if you previously testing with the same pid e.g testing the net lwip webserver. You could try to test with a new pc, or try to change the pid value or uninstall current driver for your pid.

Note: windows use vid + pid + bcd combination to cache the driver binding, it won't perform configuration parsing if the device is previously recognized and just use the cached driver for fast enumeration.

[Wini-Buh]

Made a test with a changed PID and the "CDC-RNDIS" descriptor definition. Windows installs a new driver for it, but in the device manager the RNDIS device is marked as not ready (device could not be started). So it doesn't seems a problem with the caching. Could you see anything in the previously attached data files ?

[Wini-Buh]

@hathach Sorry to trouble you again. Did you found some time to have a look into the previously attached data files ?

I also tried to connect to a mobile telephone running Android 11 using a serial app "Serial USB Terminal 1.45". It has the same behaviour like the Windows host. If the RNDIS interface is defined before the CDC in the descriptor, it is not possible to communicate over the terminal. The Serial USB Terminal shows the USB device correctly, but a communication is not possible. If the ordering is changed the serial communication is working with the Android host.

[hathach]

@Wini-Buh sorry, I am too busy with other paid work and haven't looked at this issue. Regarding the Android issue, you could try to get its kernel message to see if there is any useful info there.

Btw: you should provide an minimal example compilable in similar fashion to net_lwip_webserver for others and me (when having time) to reproduce it. Also you should also try to run it on other mcus to make sure it is not rx specific issue.

[Wini-Buh]

@Wini-Buh sorry, I am too busy with other paid work and haven't looked at this issue.

No problem at all, I understand that

Regarding the Android issue, you could try to get its kernel message to see if there is any useful info there.

Ok, I can try that... It's not very urgent at the moment

Btw: you should provide an minimal example compilable in similar fashion to net_lwip_webserver for others and me (when having time) to reproduce it. Also you should also try to run it on other mcus to make sure it is not rx specific issue.

I will expand/modify the net_lwip_webserver example to reproduce the problem. Unfortunately I can't try it with another MCU, because all hardware with USB, which I own is only equipped with RX controllers.