RTL8821CU_RTL8811CU_driver version v5.8.1

RTL8811CU and RTL8821CU driver

The Realtek RTL8811CU-CG is a highly integrated single-chip that supports 1-stream 802.11ac solutions with Multi-user MIMO (Multiple-Input, Multiple-Output) and Wireless LAN (WLAN) USB interface controller. It combines a WLAN MAC, a 1T1R capable WLAN baseband, and RF in a single chip. The RTL8811CU-CG provides an outstanding solution for a high-performance integrated wireless device.:

• USB high speed interface
• 802.11ac/abgn, 802.11ac
• 2.4 GHz Support
• 5.8 GHz Support
• Supports concurrent mode (operates as two virtual WLAN interfaces)
• MIMO config - 1x1
• MU-MIMO
• AC wave2
• 256 QAM

Driver features

• IEEE 802.11 b/g/n/ac WiFi compliant
• 802.1x, WEP, WPA TKIP and WPA2 AES/Mixed mode for PSK and TLS (Radius)
• WPA3 SAE (Personal)
• WPS - PIN and PBC Methods
• IEEE 802.11b/g/n/ac Client mode
  • Support wireless security for WEP, WPA TKIP and WPA2 AES PSK
  • Support site survey scan and manual connect
  • Support WPA/WPA2 TLS client
  • Support power saving mode
• Soft AP mode
• WiFi-Direct
• Miracast
• MU-MIMO
• BT-COEXist
• Mesh
• Wake on WLAN

Platform support

• Linux (kernel 2.6.18 ~ 5.x)
• Android 1.6 ~ 2.3, 4.0 ~ 9.x

Linux driver support

The Linux driver appears as 8821cu.ko. Check if the USB sub-system recognizes the device.

uname -a
Linux nes3 4.19.0-6-amd64 #1 SMP Debian 4.19.67-2+deb10u2 (2019-11-11) x86_64 GNU/Linux

lsusb | grep Realtek
Bus 001 Device 003: ID 0bda:c811 Realtek Semiconductor Corp.

lsmod | grep 8821cu
8821cu               2260992  0
cfg80211              589824  1 8821cu
usbcore               253952  6 ehci_hcd,xhci_pci,btusb,8821cu,xhci_hcd,ehci_pci

If 8821cu is present, everything is good to go!

Building the driver

If the driver is not present, it can be built using the included driver sources.

• Driver version : rtl8821CU_WiFi_linux_v5.8.1_34171.20190628_COEX20190509-4141
• Driver changelog.pdf
• Build tools - Install build tools, if needed (see below)

# Install build tools
sudo apt-get install build-essential -y
sudo apt-get install bc -y
sudo apt-get install unzip git -y

# install kernel headers
sudo apt-get install linux-headers-$(uname -r)

# check
apt search linux-headers-$(uname -r)
ls -l /usr/src/linux-headers-$(uname -r)

Option 1 - Direct build

git clone https://github.com/axiomware/RTL8821CU_driver_v5.8.1.git
cd RTL8821CU_driver_v5.8.1

Following customizations have been made to the default Makefile(see installation document for details):

• Choose x86 target
• Concurrent mode enabled (To disable, comment out EXTRA_CFLAGS += -DCONFIG_CONCURRENT_MODE)
• Mesh point enabled (To disable, comment out EXTRA_CFLAGS += -DCONFIG_RTW_MESH)
• Monitor mode enabled (To disable, set CONFIG_WIFI_MONITOR = n)
• Log Level = 3 (default is 4, set CONFIG_RTW_LOG_LEVEL = 4)

# Build
make

# install
sudo make install

# reboot to start the wireless module or use modprobe to load the driver
sudo modprobe 8821cu

#uninstall the driver using make
sudo make uninstall

# or uninstall directly if make is not installed
KVER=$(uname -r)
MODFILE=/lib/modules/$KVER/kernel/drivers/net/wireless/8821cu.ko
sudo rm -f $MODFILE
sudo /sbin/depmod -a $KVER

Option 2 - DKMS build (verified on Debian 10 LTS with Kernel version 4.19)

DKMS is a system which will automatically recompile and install a kernel module when a new kernel gets installed or updated. To make use of DKMS, install the dkms package and follow the steps listed below:

sudo apt-get install dkms

DRV_NAME=rtl8821CU
DRV_VERSION=5.8.1

git clone https://github.com/axiomware/RTL8821CU_driver_v5.8.1.git

# Modify Makefile, if needed (see installation document for details)
# default Makefile is for:
# x86 target
# Concurrent mode enabled
# Monitor mode enabled
# Mesh point

sudo cp -r  RTL8821CU_driver_v5.8.1 /usr/src/${DRV_NAME}-${DRV_VERSION}

# Build and install
sudo dkms add -m ${DRV_NAME} -v ${DRV_VERSION}
sudo dkms build -m ${DRV_NAME} -v ${DRV_VERSION}
sudo dkms install -m ${DRV_NAME} -v ${DRV_VERSION}

# reboot to start the wireless module or use modprobe to load the driver
sudo modprobe 8821cu

# To remove a driver, do the following:
DRV_NAME=rtl8821CU
DRV_VERSION=5.8.1
sudo dkms remove ${DRV_NAME}/${DRV_VERSION} --all

Test Driver

sudo iwconfig
enp3s0    no wireless extensions.

enp1s0    no wireless extensions.

wlx30eb1f04ecad  unassociated  Nickname:"<WIFI@REALTEK>"
          Mode:Auto  Frequency=2.412 GHz  Access Point: Not-Associated
          Sensitivity:0/0
          Retry:off   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:off
          Link Quality:0  Signal level:0  Noise level:0
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0

enp2s0    no wireless extensions.

lo        no wireless extensions.

wlp0s18u1u2  unassociated  Nickname:"<WIFI@REALTEK>"
          Mode:Auto  Frequency=2.412 GHz  Access Point: Not-Associated
          Sensitivity:0/0
          Retry:off   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:off
          Link Quality:0  Signal level:0  Noise level:0
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0