# Co-Crystal Oscillator CSI Reception Example * [中文版](./README_CN.md) This example provides a radio frequency phase synchronization solution for Wi-Fi CSI, including three sub-projects: `MASTER_RECV` (master receiver), `SLAVE_RECV` (slave receiver), and `SLAVE_SEND` (slave sender). The solution includes two working modes: 1. Self-transmit-and-receive mode 2. Single-transmit-and-dual-receive mode ## Feature Introduction ### 1. Self-Transmit-and-Receive Mode In this mode, two ESP32-C5 chips are used to transmit and receive signals respectively. By analyzing the phase information in the received Wi-Fi CSI signals, disturbances in the signal path can be sensed with millimeter-level accuracy. By installing copper sheets to control the RF signal transmission path, the sensing range can also be adjusted, thus supporting high-precision short-range Wi-Fi sensing. This enables finer Wi-Fi signal sensing, suitable for precise applications in close-range and complex environments. ![Self-Transmission and Reception Amplitude]() ![Self-Transmission and Reception Phase]() #### 1.1 MASTER_RECV (Master Receiver) Flash the `MASTER_RECV` firmware to the **Master** chip of the `esp-crab` device. Its functions include: * Receiving Wi-Fi packets from the `SLAVE_SEND` and extracting **CIR (Channel Impulse Response)** data. * Calculating the **amplitude and phase** of Wi-Fi CSI from the CIR and displaying the results. #### 1.2 SLAVE_SEND (Slave Sender) Flash the `SLAVE_SEND` firmware to the **Slave** chip of the `esp-crab` device. Its function: * Transmitting specific Wi-Fi packets. ### 2. Single-Transmit-and-Dual-Receive Mode In this mode, one ESP32-C5 chip is responsible for signal transmission, while the two ESP32-C5 chips on the `esp-crab` device receive signals. By spatially distributing the sender and receivers, Wi-Fi sensing can be realized over a **larger area**. The **co-crystal oscillator Wi-Fi CSI data** acquired by the `esp-crab` satisfies the performance requirements of cutting-edge Wi-Fi sensing research, and can be directly integrated with advanced algorithms, further improving the **accuracy and application value** of the sensing system. This mode offers strong technical support for **wide-area and complex environment wireless sensing and positioning**. ![Single-Transmission and Dual-Reception Phase]() #### 2.1 MASTER_RECV (Master Receiver) Flash the `MASTER_RECV` firmware to the **Master** chip of the `esp-crab` device. Its functions include: * Receiving Wi-Fi packets from `SLAVE_SEND` via antenna and extracting **CIR data**. * Receiving CIR data from the `SLAVE_RECV` chip (collected via its antenna). * Calculating the **amplitude and phase difference** of Wi-Fi CSI and displaying the result. #### 2.2 SLAVE_RECV (Slave Receiver) Flash the `SLAVE_RECV` firmware to the **Slave** chip of the `esp-crab` device. It supports two modes: * Receiving Wi-Fi packets from `SLAVE_SEND` and extracting **CIR data**. * Transmitting the CIR data to `MASTER_RECV`. #### 2.3 SLAVE_SEND (Slave Sender) Flash the `SLAVE_SEND` firmware to an extra **ESP32-C5 chip** (e.g., `ESP32-C5-DevkitC-1`). Its function: * Transmitting specific Wi-Fi packets. ## Required Hardware ### `esp-crab` Device #### PCB Overview The RF phase synchronization solution must run on the `esp-crab` device. The images below show the front and back of the PCB: | No. | Function | |-----|-----------------------------------| | 1 | Master external antenna | | 2 | Master onboard antenna | | 3 | Slave external antenna | | 4 | Slave onboard antenna | | 5 | Master BOOT button | | 6 | Master ADC button | | 7 | Slave BOOT button | | 8 | Master 2.4G antenna switch resistor | | 9 | Master 5G antenna switch resistor | | 10 | Slave 5G antenna switch resistor | | 11 | Slave 2.4G antenna switch resistor | | 12 | RST button | ![esp_crab_pcb_front](doc/img/esp_crab_pcb_front.png) ![esp_crab_pcb_back](doc/img/esp_crab_pcb_back.jpg) Refer to [ESP-Crab Circuit Diagram Explanation]() for the PCB pin description. #### Device Form Factor The `esp-crab` device has two casing styles based on mode: * Spaceship case for Self-transmit-and-receive mode ![Alt text](doc/img/shape_style.png) * Router-style case for Single-transmit-and-dual-receive mode ![router_shape](doc/img/router_style.png) ### `ESP32-C5-DevkitC-1` Development Board The Single-transmit-and-dual-receive mode requires an `ESP32-C5-DevkitC-1` board as the Wi-Fi sender. ## How to Use the Example ### 1. Self-Transmit-and-Receive Mode Power the `esp-crab` via Type-C and it will begin operation. It will display CSI amplitude and phase: * **Amplitude**: Two curves representing CIR amplitude for -Nsr~0 and 0~Nsr. * **Phase**: A standard sine curve. The intersection with the red center line represents the CIR phase for 0~Nsr. At the same time, `esp-crab` will print received CSI data to the serial port in the following format: `type,id,mac,rssi,rate,noise_floor,fft_gain,agc_gain,channel,local_timestamp,sig_len,rx_state,len,first_word,data` Example: ``` text CSI_DATA,3537,1a:00:00:00:00:00,-17,11,159,22,5,8,859517,47,0,234,0,"[14,9,13,...,-11]" ``` > **Note:** Upon power-up, the device collects the first 100 Wi-Fi packets to determine the RF reception gain. ### 2. Single-Transmit-and-Dual-Receive Mode In this mode, both the `esp-crab` and the `ESP32-C5-DevkitC-1` need to be powered and placed at a certain distance from each other. The `esp-crab` will then display the amplitude and phase information of the CSI, and simultaneously print the received `CSI` data to the serial port, as described earlier.