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Get Started Examples[中文]

This example demonstrates how to obtain CSI data through communication between two espressif chips, and uses a graphical interface to display real-time data of CSI subcarriers

hardware

You need to prepare two development boards for espressif chips, one as the sender and the other as the receiver

example_display

In order to ensure the perception effect of CSI, please do your best to meet the following requirements

  1. Use ESP32-C3 / ESP32-S3: ESP32-C3 / ESP32-S3 is the best RF chip at present
  2. Use an external antenna: PCB antenna has poor directivity and is easily interfered by the motherboard
  3. The distance between the two devices is more than one meter

Binding

  1. Burn the firmware of csi_recv and csi_send on two development boards respectively

    device_log

    # csi_send
cd esp-csi/examples/get-started/csi_send
idf.py set-target esp32c3
idf.py flash -b 921600 -p /dev/ttyUSB0 monitor

# csi_recv
cd esp-csi/examples/get-started/csi_recv
idf.py set-target esp32c3
idf.py flash -b 921600 -p /dev/ttyUSB1

  2. Run csi_data_read_parse.py in csi_recv for data analysis. Please close idf.py monitor before running

    cd esp-csi-gitlab/examples/get-started/tools

# Install python related dependencies
pip install -r requirements.txt

# Graphical display
python csi_data_read_parse.py -p /dev/ttyUSB1

CSI Data Format

Taking a line of CSI raw data as an example:

type,seq,mac,rssi,rate,sig_mode,mcs,bandwidth,smoothing,not_sounding,aggregation,stbc,fec_coding,sgi,noise_floor,ampdu_cnt,channel,secondary_channel,local_timestamp,ant,sig_len,rx_state,len,first_word,data CSI_DATA,0,94:d9:b3:80:8c:81,-30,11,1,6,1,0,1,0,1,0,0,-93,0,13,2,2751923,0,67,0,128,1,"[67,48,4,0,0,0,0,0,0,0,5,0,20,1,20,1,19,0,17,1,16,2,15,2,14,1,12,0,12,-1,12,-3,12,-4,13,-6,15,-7,16,-8,16,-8,16,-8,16,-6,15,-5,15,-4,14,-4,13,-4,12,-4,11,-4,10,-4,9,-5,8,-6,4,-4,8,-9,9,-10,9,-10,10,-11,11,-10,11,-10,12,-9,11,-8,11,-7,10,-6,9,-6,7,-6,6,-7,5,-7,5,-8,5,-9,5,-10,5,-11,5,-11,6,-11,7,-11,8,-11,9,-10,9,-9,8,-8,8,-7,1,-2,0,0,0,0,0,0,0,0]"

  • Metadata Fields: Including type, seq, mac, rssi, rate, sig_mode, mcs, bandwidth, smoothing, not_sounding, aggregation, stbc, fec_coding, sgi, noise_floor, ampdu_cnt, channel, secondary_channel, local_timestamp, ant, sig_len, rx_state, len, first_word, etc.
  • CSI Data: Stored in the last item data array, enclosed in [...]. It contains the channel state information for each subcarrier. For detailed structure, refer to the Long Training Field (LTF) section of the ESP-WIFI-CSI Guide. For each subcarrier, the imaginary part is stored first, followed by the real part (i.e., [Imaginary part of subcarrier 1, Real part of subcarrier 1, Imaginary part of subcarrier 2, Real part of subcarrier 2, Imaginary part of subcarrier 3, Real part of subcarrier 3, ...]). The order of LTF is: LLTF, HT-LTF, STBC-HT-LTF. Depending on the channel and grouping information, not all 3 LTFs may appear.

A&Q

1. csi_send prints no memory

  • Phenomenon: The following log appears on the serial port: 
      W (510693) csi_send: <ESP_ERR_ESPNOW_NO_MEM> ESP-NOW send error
  • Reason: The current channel is congested causing congestion in sending packets, so that the ESP-NOW buffer space is full
  • Solution: Change the Wi-Fi channel or change to a place with a better network environment

2. csi_data_read_parse.py Serial port printing exception

  • Phenomenon: The following log appears on the serial port: 
        element number is not equal
    data is not incomplete
  • Reason: PYQT takes up a lot of CPU when drawing, causing the PC to be unable to read the serial port buffer queue in time, resulting in data confusion
  • Solution: Advance the baud rate of the serial port