Activation Codes and Methods, Hardware Details, Sniffing
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n0rdik
Posts: 3
Joined: Wed May 13, 2020 8:01 pm

Realtek RTL8821CU 0bda:1a2b

Post by n0rdik » Wed May 13, 2020 8:10 pm

Hi! I buyed this usb wifi dongle: https://www.aliexpress.com/item/4000086 ... 63c0ic2aNm

I want to use it with Android (6.1.1, Odroid C2), but it has a previous usb mass storage mode (0bda:1a2b) to get the install executable for windows/mac. I need to mode switch it to 0bda:c811 to get it recognized as a wifi dongle. I've installed the ppp widget 3 but it does nothing. In linux works like a charm the usb_modeswitch executable (tested in coreelec). What should I do? Thanks in advance.

LOM
Posts: 1308
Joined: Wed Jul 11, 2012 3:14 pm
Location: Koh Samui, TH

Re: Realtek RTL8821CU 0bda:1a2b

Post by LOM » Thu May 14, 2020 4:06 am

n0rdik wrote:
Wed May 13, 2020 8:10 pm
What should I do? Thanks in advance.
The support for 0bda:1a2b was included in a late Nov 2019 release of usb_modeswitch, the pppwidget project is currently in deep sleep so there is no updated pppwidget that you can install.
Android 6.1.1, if it includes usb_modeswitch at all then it is likely an old version.

You could try to eject the storage device that has been created by the usb mass storage device in your dongle.
Consult the Android 6.1.1 documentation to see if it is possible to do and how to do it.

n0rdik
Posts: 3
Joined: Wed May 13, 2020 8:01 pm

Re: Realtek RTL8821CU 0bda:1a2b

Post by n0rdik » Thu May 14, 2020 2:01 pm

Well I found this:

https://github.com/joerg65/usb_modeswitch_Android

Just 7 days ago this project started, so lucky. I compiled and executed and voila!, the lsusb command now shows 0bda:c811. But... no way to make android get it recognized. In /system/etc/wifi_id_list.txt is an entry: "0bda c811 8821cu /system/etc/modprobe.d/8821cu", so it should be recognized. I've tried with insmod, modprobe, but nothing works. I think I'm giving up...

LOM
Posts: 1308
Joined: Wed Jul 11, 2012 3:14 pm
Location: Koh Samui, TH

Re: Realtek RTL8821CU 0bda:1a2b

Post by LOM » Thu May 14, 2020 5:03 pm

lsmod shows loaded modules, if it doesn't show after modprobe or insmod then the module is not present in the module directory.

I can't find driver support for 8821cu in linux and google says that you have to compile the driver yourself using source that is available from Realtek.

n0rdik
Posts: 3
Joined: Wed May 13, 2020 8:01 pm

Re: Realtek RTL8821CU 0bda:1a2b

Post by n0rdik » Fri May 15, 2020 8:02 pm

The official android ROM for the Odroid C2 has support for 8821cu. In fact, after doing the USB modeswitch, I do an insmod of the driver and I can see it with lsmod (and also 2 more modules as "/system/etc/modprobe.d/8821cu" says), but nothing, the blue led doesn't flash and if I activate the wifi nothing occurs. I think that after modeswitching, the system doesn't detect any change, I don't know...

LOM
Posts: 1308
Joined: Wed Jul 11, 2012 3:14 pm
Location: Koh Samui, TH

Re: Realtek RTL8821CU 0bda:1a2b

Post by LOM » Sat May 16, 2020 7:01 am

n0rdik wrote:
Fri May 15, 2020 8:02 pm
I think that after modeswitching, the system doesn't detect any change, I don't know...
Your system log, after the dongle being switched to 0bdb:c811, should show the 8821cu driver binding to the dongle and creating a new net device. lsmod should also show a usage count for 8821cu.
When driver binding has taken place then there should be a new wlan or wifi device visible in the output from the ifconfig or the ip command.

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