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RPi Zero connect via OTG g_ether to Windows 10 not working

Posted: Tue Jul 09, 2019 4:24 pm
by beta-tester
hello,
i just bought a RPi Zero W (rev 1.3) and tried to connect it directly via "OTG ehternet gadget" to my PC with Windows 10 64bit.
normally the RPiZ should appear as a RNDIS network adapter in the windows device manager...
but for some reason the RPiZ appears as a "serial port (COM 3)" only.

what i am doing wrong?
- i am using the newest "2019-06-20-raspbian-buster-lite.zip" and flashed it to a SD-card.
- i modified the cmdline.txt file:

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dwc_otg.lpm_enable=0 console=serial0,115200 console=tty1 root=PARTUUID=0634f60c-02 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait modules-load=dwc2,g_ether quiet init=/usr/lib/raspi-config/init_resize.sh
- i modified the config.txt file:

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# added to the end of config.txt file
dtoverlay=dwc2
- and added an empty "ssh" file to the boot partition, to enable ssh.
- i connect the RPiZ via USB-cable to my PC
- after a while, windows recognized a new device...
but it is only recognized as a serial port (USB\VID_0525&PID_A4A2&REV_0419)...
nothing else... no RNDIS adapter... no unknown adapter... or something else.
(when i search in the internet, there is a link to microsoft update catalog for that "VID_0525, PID_A4A2", but when i try to download, then it tells, that ressource doesn't exist)

Re: RPi Zero connect via OTG g_ether to Windows 10 not working

Posted: Tue Jul 09, 2019 7:40 pm
by neilgl
Maybe have a look at this post from 2018:
https://www.raspberrypi.org/forums/view ... p?t=221259

As a test, I used etcher to put Buster lite onto a 32GB microSD card, edited config.txt & cmdline.txt, added ssh, then put it in my pizeroW.
Connected to my Windows 10 PC using a USB cable - it detected a USB Ethernet/RNDIS Gadget.
I did an update driver on Windows 10 (Pick from a list)
Then we can see on the Win 10 PC:

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Ethernet adapter pizero:

   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : USB Ethernet/RNDIS Gadget #2
So it may be a Windows configuration problem?

Re: RPi Zero connect via OTG g_ether to Windows 10 not working

Posted: Tue Jul 09, 2019 9:11 pm
by beta-tester
that's very strange... i plugged the RPiZ to an other Windows 10 Pro (1903) computer and observed what happen...
first, windows told that it found an RNDIS device... after few seconds the RNDIS disappeared and changed to a serial port device.
then windows told the new serial port device is ready to use.

with this in mind, i went to a third windows 10 Pro (1903) computer.
then i disconnected that computer from the internet, to prevent it from searching for a updated driver.
and the i plugged in the RPiZ...
but again the exact same sequence... first, windows saw a RNDIS device... then it disapeared and changed to a serial port device.
and i thought the windows driver update was the reason why the device driver was that strange...

long story short... i found a proper driver on the microsoft update catalog page...
  • i searched for the vendor and product id of what the "serial port" told.
    https://www.catalog.update.microsoft.co ... 26pid_a4a2
    and it gave me a "Acer Incorporated. - Other hardware - USB Ethernet/RNDIS Gadget" in different "flavors".
    i took the "Windows 7,Windows 8,Windows 8.1 and later drivers" download.
  • i downloaded the CAB file and extracted to a folder.
  • it contains a "RNDIS.CAT" and a "RNDIS.INF" file.
    the driver is for two product ids

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    %RndisDevice.COMM%	= RNDIS.NT.5.1, USB\VID_0525&PID_A4A2
    %RndisDevice.ACER%	= RNDIS.NT.5.1, USB\VID_0502&PID_3210
    ...
    RndisDevice.COMM	= "USB Ethernet/RNDIS Gadget"
    RndisDevice.ACER	= "Acer Netchip RNDIS/Ethernet Gadget"
    
    the product id of the RPiZ is the "USB Ethernet/RNDIS Gadget".
  • then i opened the device manager of windows 10 and navigated to the "Serial Port (COM ...)" that has the USB\VID_0525&PID_A4A2 vendor/product id.
  • made a right click on that device and choosed update driver
  • then i choosed search on this computer for device driver and selected the folder where i extracted the downloaded CAB file
  • after choosing, then the RNDIS driver was installed and the Serial Port device changed to an RNDIS device.
now the RPiZ shows up as "USB Ethernet/RNDIS Gadget" device as expected in Windows 10 (1903)
and i can use the new network interface ...
... everything went well :mrgreen:

but i have no idea why Windows 10 Pro (1903) shows that odd behavior with first detecting a RNDIS device and then flip it to a Serial Port device.