Create fpv-bl-m8812eu2-wifi-adaptors.md (#348)

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+# OpenIPC Wiki
+[Table of Content](../README.md)
+
+Instructions for Using BL-M8812EU2 (or other RTL8812EU-based) Wi-Fi Module in FPV Firmware
+---
+[LB-LINK's BL-M8812EU2 module](https://www.lb-link.com/product_36_183.html)  
+Another FPV Wi-Fi adaptor choice with high TX power (>29dBm) and low cost.   
+![image](https://github.com/libc0607/openipc-wiki/assets/8705034/8aed1797-8f58-4e8f-95d7-b8d055c3519a)
+
+
+### Hardware 
+#### Where to buy
+Since the RTL8812EU chip is fairly new, there are no sellers on Aliexpress now.   
+But when considering that it comes from the same supplier as the widely sold BL-R8812AF1, it's only a matter of time before it becomes readily available.   
+However, you can still find any Taobao agent and buy the module from [here](https://item.taobao.com/item.htm?id=764510955987). 
+
+#### Wiring
+![image](https://github.com/libc0607/openipc-wiki/assets/8705034/0511de9a-bd3a-42c1-8f35-0f5ec72a1121)  
+
+Connect ```USB2.0+DP```, ```USB2.0-DM``` with a twisted wire pair to the IPC's USB. A GND connection to IPC is also required.   
+Connect ```GND``` and ```VDD5.0``` to a 5V/>3A power supply to power the module.   
+Connect two 5GHz antennas to the IPEX connector J0 and J1 before transmission.   
+The Pin 9~18 are GND and can be left floating.  
+
+Ref.: https://oshwhub.com/libc0607/bl-m8812eu2-demoboard-v1p0  
+
+### Add the Driver to OpenIPC Firmware
+Because of the very limited flash space, the driver is disabled by default.  
+You need to compile firmware from source code to enable it.  
+
+#### Step 1. Prepare
+Follow the guide in [source-code.md](https://github.com/libc0607/openipc-wiki/blob/master/en/source-code.md) till you successfully build your firmware.
+
+#### Step 2. Add BR2_PACKAGE to Board Config  
+Find your target board config in ```br-ext-chip-*/config```, then add  ```BR2_PACKAGE_RTL88X2EU_OPENIPC=y``` to it. 
+If your IPC has an 8M/16M NOR Flash, you may need to disable other drivers (e.g. RTL8812AU) to save space. 
+
+#### Step 3. Check CONFIG_WIRELESS_EXT in Kernel Config
+The driver needs ```CONFIG_WIRELESS_EXT``` enabled in kernel config, which can be found at ```br-ext-chip-*/board/*/kernel/*-fpv.config```.
+This macro has been set in SigmaStar, but you should check it when using Hisilicon or GOKE.
+
+#### Step 4. Build the firmware 
+```
+make
+```
+Then you can use ```output/images/rootfs.squashfs.*``` and ```output/images/uImage.*``` with ```sysupgrade```.
+
+### Usage
+It's almost the same as RTL8812AU adaptors. 
+
+#### Set TX Power  
+There are two ways to set TX power.   
+- ```driver_txpower_override``` in ```/etc/wfb.conf```. The range is ```0~63```
+- ```iw dev <wlan0> set txpower fixed <mBm>```. The range is ```0~3150```, and can be set dynamically when transmitting.
+
+For the BL-M8812EU2 module, I recommend setting ```driver_txpower_override``` to ```40~50``` as a higher value causes the amplifier to be saturated.  
+The power consumption of a BL-M8812EU2 module can reach 5V/2.xA when ```driver_txpower_override > ~40```.  
+Use a proper 5V power supply and a HEAT SINK WITH FAN.
+