129 lines
5.9 KiB
Markdown
129 lines
5.9 KiB
Markdown
# Co-Crystal Oscillator CSI Reception Example
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* [中文版](./README_CN.md)
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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).
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The solution includes two working modes:
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1. Self-transmit-and-receive mode
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2. Single-transmit-and-dual-receive mode
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## Feature Introduction
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### 1. Self-Transmit-and-Receive Mode
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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.
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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.
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This enables finer Wi-Fi signal sensing, suitable for precise applications in close-range and complex environments.
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#### 1.1 MASTER_RECV (Master Receiver)
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Flash the `MASTER_RECV` firmware to the **Master** chip of the `esp-crab` device. Its functions include:
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* Receiving Wi-Fi packets from the `SLAVE_SEND` and extracting **CIR (Channel Impulse Response)** data.
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* Calculating the **amplitude and phase** of Wi-Fi CSI from the CIR and displaying the results.
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#### 1.2 SLAVE_SEND (Slave Sender)
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Flash the `SLAVE_SEND` firmware to the **Slave** chip of the `esp-crab` device. Its function:
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* Transmitting specific Wi-Fi packets.
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### 2. Single-Transmit-and-Dual-Receive Mode
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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.
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By spatially distributing the sender and receivers, Wi-Fi sensing can be realized over a **larger area**.
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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.
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This mode offers strong technical support for **wide-area and complex environment wireless sensing and positioning**.
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#### 2.1 MASTER_RECV (Master Receiver)
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Flash the `MASTER_RECV` firmware to the **Master** chip of the `esp-crab` device. Its functions include:
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* Receiving Wi-Fi packets from `SLAVE_SEND` via antenna and extracting **CIR data**.
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* Receiving CIR data from the `SLAVE_RECV` chip (collected via its antenna).
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* Calculating the **amplitude and phase difference** of Wi-Fi CSI and displaying the result.
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#### 2.2 SLAVE_RECV (Slave Receiver)
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Flash the `SLAVE_RECV` firmware to the **Slave** chip of the `esp-crab` device. It supports two modes:
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* Receiving Wi-Fi packets from `SLAVE_SEND` and extracting **CIR data**.
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* Transmitting the CIR data to `MASTER_RECV`.
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#### 2.3 SLAVE_SEND (Slave Sender)
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Flash the `SLAVE_SEND` firmware to an extra **ESP32-C5 chip** (e.g., `ESP32-C5-DevkitC-1`). Its function:
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* Transmitting specific Wi-Fi packets.
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## Required Hardware
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### `esp-crab` Device
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#### PCB Overview
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The RF phase synchronization solution must run on the `esp-crab` device. The images below show the front and back of the PCB:
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| No. | Function |
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|-----|-----------------------------------|
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| 1 | Master external antenna |
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| 2 | Master onboard antenna |
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| 3 | Slave external antenna |
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| 4 | Slave onboard antenna |
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| 5 | Master BOOT button |
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| 6 | Master ADC button |
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| 7 | Slave BOOT button |
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| 8 | Master 2.4G antenna switch resistor |
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| 9 | Master 5G antenna switch resistor |
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| 10 | Slave 5G antenna switch resistor |
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| 11 | Slave 2.4G antenna switch resistor |
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| 12 | RST button |
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Refer to [ESP-Crab Circuit Diagram Explanation](<doc/ESP-Crab circuit diagram explanation.pdf>) for the PCB pin description.
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#### Device Form Factor
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The `esp-crab` device has two casing styles based on mode:
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* Spaceship case for Self-transmit-and-receive mode
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* Router-style case for Single-transmit-and-dual-receive mode
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### `ESP32-C5-DevkitC-1` Development Board
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The Single-transmit-and-dual-receive mode requires an `ESP32-C5-DevkitC-1` board as the Wi-Fi sender.
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## How to Use the Example
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### 1. Self-Transmit-and-Receive Mode
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Power the `esp-crab` via Type-C and it will begin operation. It will display CSI amplitude and phase:
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* **Amplitude**: Two curves representing CIR amplitude for -Nsr~0 and 0~Nsr.
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* **Phase**: A standard sine curve. The intersection with the red center line represents the CIR phase for 0~Nsr.
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At the same time, `esp-crab` will print received CSI data to the serial port in the following format:
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`type,id,mac,rssi,rate,noise_floor,fft_gain,agc_gain,channel,local_timestamp,sig_len,rx_state,len,first_word,data`
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Example:
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``` text
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CSI_DATA,3537,1a:00:00:00:00:00,-17,11,159,22,5,8,859517,47,0,234,0,"[14,9,13,...,-11]"
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```
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> **Note:** Upon power-up, the device collects the first 100 Wi-Fi packets to determine the RF reception gain.
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### 2. Single-Transmit-and-Dual-Receive Mode
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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.
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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.
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