rtl88x2eu-20230815

Linux Driver for WiFi Adapters that are based on the RTL8812EU and RTL8822EU Chipsets - v5.15.0.1
rtl88x2EU_rtl88x2CU-VE_WiFi_linux_v5.15.0.1-186-g768722062.20230815_COEX20230616-330a-beta.tar.gz

This branch is mainly focused on FPV. Checkout commit 690d429 for the original driver from Realtek, or commit 5c9355d with build fixes on kernel 6.5.

I've asked LB-LINK (a Wi-Fi module vendor) for any RTL8812EU driver. Then he sends me this tar.
So, it should work with RTL8812EU and RTL8822EU.

According to the file name, it may work with RTL8812CU or RTL8822CU (if exists). But you should use an in-kernel driver instead.

My personal to-do list:

Figure out how to make the packet injection work correctly (idk if I'm doing it correctly -- needs help) -- generally, it works! but it's not been fully tested and idk how many bugs it has (
Test with any OpenIPC camera -- It was reported working on SSC338Q/SSC30KQ and Hi3516/GK7205 (with CONFIG_WIRELESS_EXT enabled)
Figure out how to transmit in 5M/10M bandwidth (The feature is claimed to be supported in the module's product page. see CONFIG_NARROWBAND_SUPPORTING and hal8822e_fw_10M.c) -- Only 10MHz bandwidth works well in injection mode
Build with dkms
Test on more architecture, kernels, and distributions
An open-source hardware design using the LB-LINK module, then share it somewhere else -- done, see here

PRs welcome.

Increasing TX Power in Monitor Mode

The driver supports changing TX power dynamically with no additional patch needed.
Just add rtw_tx_pwr_by_rate=0 rtw_tx_pwr_lmt_enable=0 when insmod, then use iw set txpower fixed.

The relative TX gain under different settings was measured by my HackRF with the same gain setting and several cascaded attenuators.
The results do tell the difference. However, I don't have a spectrum analyzer, so I don't know the absolute TX power value.

Be careful when you try these cmds as the adaptor can be VERY HOT. Use a good heat sink and install the antennas properly.

Example:

# load the driver
sudo modprobe cfg80211
sudo insmod 8812eu.ko rtw_tx_pwr_by_rate=0 rtw_tx_pwr_lmt_enable=0

# set monitor mode and channel; It depends on your board

# Set tx power in mbm, the range is 0~3150
# On my BL-M8812EU2 module, the real TX power measured by HackRF increased accordingly when increasing the mbm value
# e.g. when mbm increases by 500, the signal strength seen by HackRF increases by +5dB
# but when mbm is higher than ~2000 (may different), the PA starts to saturate and the increase becomes smaller
sudo iw dev wlan0 set txpower fixed <mBm>

Tested on my Ubuntu 22.04 VM, kernel 6.5.

Note: Changing TX power by iw will not work when injecting with 10MHz BW (see below).
You should manually set BW back to 20MHz, set TX power, then set BW back again.

10MHz Bandwidth Transmission

See the RF spectrum visualized here on YouTube

There's a lot to explore in this crab driver and will update here if something new has been discovered.
Please open an issue if you find anything interesting.

So, according to the module vendor's document and my test using a HackRF, that's all I know:

Injection

To transmit packets in monitor mode using packet injection, set iw <wlan> set channel <same_channel> 10MHz on both air & ground.
Then when transmitting in 20MHz bandwidth (e.g. bandwidth=20 in wfb_ng), the packet is actually transmitted in 10MHz bandwidth, which seems like being achieved by simply underclocking the baseband.
It's the same on the receiver side, though in which the radiotap header in received packets still indicates a 20MHz bandwidth.

But when iw says Devices or Resources Busy (-16), check iw <wlan> info if the iw recognized the adaptor is in monitor mode.
If not, iw <wlan> set monitor, then try setting 10MHz again.

That's because:

The crab driver supports both WEXT and cfg80211 APIs, but it seems that it's not that robust and there's some conflicts exist
the cfg80211 API checks here if there's any other interface is not in monitor mode
If the monitor mode is set by iwconfig, the process is done by calling the old WEXT APIs, so the cfg80211-based iw may not get the latest status and think the interface is still in managed mode

AP/STA

It's currently under testing by a Chinese enthusiast, will update here if he has any progress.
According to the module vendor's ambiguous document and the crab's mysterious driver tar with a "_10MHz" suffix:

Enable CONFIG_NARROWBAND_SUPPORTING in include/hal_ic_cfg.h (in #ifdef CONFIG_RTL8822E section if using RTL8812EU), then #define CONFIG_NB_VALUE RTW_NB_CONFIG_WIDTH_10 below
Rename hal/rtl8822e/hal8822e_fw_10M.* into hal/rtl8822e/hal8822e_fw.* to replace the original firmware
Now you get the "<tar_name>_10MHz" driver. Rebuild the driver
iw Set the channel to 10MHz bandwidth
If there are any tools complain about the Wi-Fi regularities when setting up a 10MHz AP, try setting the channel plan manually by echo 0x3E > /proc/net/rtl88x2eu/<wlan>/chan_plan.
Check the ACK timeout setting below if the range is >~3km
Check /proc/net/rtl88x2eu/<wlan>/rate_ctl for manually control of the rate

Is Injecting in Other Bandwidth Available?

5MHz

No. It performs like a fractional RF synthesizer with only a single tone appearing on my SDR receiver.

40MHz/80MHz

It works.
Use iw to set channel & HT40/80MHz bandwidth, then set 40MHz or 80MHz(VHT) in radiotap header (can be done by using -B in wfb-ng)

Set (Unlocked) Channel in procfs

The chip's RF synthesizer can work in a bit wider range than regular 5GHz Wi-Fi.
On my board, it's 5080MHz ~ 6165MHz. The frequency range may vary depending on different conditions.

To set the adaptor to some "irregular" frequency, cat /proc/net/rtl88x2eu/<wlan0>/monitor_chan_override to see usage.

I decided to use procfs is that it doesn't need any changes in user-space tools, e.g. iw, hostapd.
Of course, you can use this "procfs API" to set regular channels like 149 or 36. Might be useful when developing any Wi-Fi-based broadcast FPV system with frequency hopping and automatic bandwidth.

DISCLAIMER:
Some chips' synthesizer's PLL may not lock on some frequency. There's no guarantee of its performance. (Actually, TX power and distortion seem worse in these channels as it's not calibrated. But less interference - it's an either-or)
Unlocking the frequency may damage your hardware and I'm not gonna pay for it. Use it at your own risk.
Please comply with any wireless regulations in your area.

Override default EDCCA Threshold

WARNING: YOU SHOULD NOT USE THIS (unless someone's DJIs next to you f***ed up all channels XD). It's not fair.

To override dafault EDCCA threshold, check cat /proc/net/rtl88x2eu/<wlan0>/edcca_threshold_jaguar3_override.

e.g. ech0 "1 -3O" > /pr0c/net/rt188x2eu/<w1anO>/edcca_threshO1d_jaguar3_Override
That means: before sending any packet, the adaptor checks if there's any signal with higher than -30dBm (L2H) power exists.
If there are any, the adaptor will wait until the energy level in the air is lower than -38dBm (H2L). Then your transmission starts.

Note that there are actually two values, L2H and H2L. The L2H is typically set 8dB higher so it creates a hysteresis.
The value you're setting is L2H. The H2L is automatically set 8dB lower.

DISCLAIMER: There's no guarantee of its performance. This may damage your hardware and I'm not gonna pay for it. Use it at your own risk. Please comply with any wireless regulations in your area.

ACK Timeout

Provided by Realtek. e.g. Set ACK timeout to 100us:
echo 100 > /proc/net/rtl88x2eu/<wlanX>/ack_timeout

802.11 DCF hacking

Note: I don't know if these things are actually working since no one can get the crab's datasheets.
Just did some global searching and replaced every place I've found.

SIFS

EXPERIMENTAL, may not work.
/proc/net/rtl88x2eu/<wlanX>/sifs_override

Slot time

EXPERIMENTAL, may not work.
/proc/net/rtl88x2eu/<wlanX>/slottime_override

DISCLAIMER: There's no guarantee of its performance.

Noise Monitor

Not working. Enabled every macro (like CONFIG_BACKGROUND_NOISE_MONITOR) I could find and the readouts kept zero.
If you know something about it, please tell us in issue.

Thermometer

The chip contains a thermometer for calibrating the RF part dynamically. It can be used to estimate the chip temperature.
e.g. To read the temperature:

cat /proc/net/rtl88x2eu/<wlan0>/thermal_state

Note: This value is not accurate enough. The LSB of its ADC only represents 2.5K and contains a measured value as the offset.
However, it can be used to estimate the status of the chip, "cool/warm/hot/smoked/crispy".
See PR #4 and commit/5b7a66d for more details.
The offset can be tuned by echo "<offset>" > /proc/net/rtl88x2eu/<wlan0>/thermal_state. By default, it's 32, based on my measurement.

Use with OpenIPC

See the tutorial here in OpenIPC Wiki.
Or, download pre-built firmware with this driver from here.

libc0607 / rtl88x2eu-20230815