One super power of the openwifi platform is "**Full Duplex**" which means that openwifi baseband can receive its own TX signal. Just like a radar! This brings a unique capability of "**joint radar and communication**" to openwifi. For instance, put two directional antennas to openwifi TX and RX, and the **CSI** (Channel State Information) of the self-TX signal will refect the change of the target object.  ## Quick start - Power on the SDR board. - Connect a computer to the SDR board via Ethernet cable. The computer should have static IP 192.168.10.1. Open a terminal on the computer, and then in the terminal: ``` ssh root@192.168.10.122 (password: openwifi) cd openwifi ./fosdem.sh (After the AP started by above command, you can connect a WiFi client to this openwifi AP) (Or setup other scenario according to your requirement) ifconfig (Write down the openwifi AP MAC address. For example 66:55:44:33:22:5a) insmod side_ch.ko num_eq_init=0 ./side_ch_ctl wh1h4001 ./side_ch_ctl wh7h4433225a (Above two commands ensure receiving CSI only from XX:XX:44:33:22:5a. In this case, it is the openwifi self-TX) ./sdrctl dev sdr0 set reg xpu 1 1 (Above unmute the baseband self-receiving to receive openwifi own TX signal/packet) ./side_ch_ctl g0 ``` You should see on board outputs like: ``` loop 64 side info count 4 loop 128 side info count 5 ... ``` If the second number (4, 5, ...) keeps increasing, that means the CSI is going to the computer smoothly. - On your computer (NOT ssh onboard!), run: ``` cd openwifi/user_space/side_ch_ctl_src python3 side_info_display.py 0 ``` The python script needs "matplotlib.pyplot" and "numpy" packages installed. Now you should see figures showing run-time **CSI** and **frequency offset**. Meanwhile the python script prints the **timestamp**.  While running, all CSI data is also stored into a file **side_info.txt**. A matlab script **test_side_info_file_display.m** is offered to help you do CSI analysis offline. In this case, run **test_side_info_file_display(0)** in Matlab.  The following picture is generated by data processing on the captured openwifi CSI while people move in front of two directional antennas (Tx/Rx antenna).  Please learn the python and Matlab script for CSI data structure per packet according to your requirement. Do read the [normal CSI app note](csi.md) to understand the basic implementation architecture.