This project allows to stream digital signal coming from a GPIO port of an ESP32 through serial, and store and visualize it in the computer. For me, it has been helpful as an incredibly cheap 433 MHz receiver for doing development. The most I was able to achieve is sending a signal sampled at a frequency of 100 KHz using a serial port with 128k baud rate.
It consists on two pieces of software:
-
ESP32 program: The program based on esp-idf that is flashed into the ESP32 for collecting and sending the data to the computer. By default, it uses the main USB serial port of ESP32 for logs and diagnostics, while the raw signal data is sent through the secondary serial ports, that can be read from the computer using a USB-to-UART module.
-
esp32-samples-reader: A Rust program (Could have been done in Python, but where's the fun in that) that allows you to read the samples and 1) store it in a Wave file or 2) stream it as PCM audio to Pulseaudio so it can be recorded in realtime using tools like Audacity.
- Edit the definitions of the
main/signalreader.cfile for changing the configuration of the program (GPIO ports, baud rate, sample rate, etc). - Check esp-idf documentation for more information about how to install the development tools from Espressif for being able to build and flash the program.
- Flash the program using
idf.py -p /dev/tty<device> flash monitor.
Once the program is running in the ESP32 and your computer is connected to the external ESP32 serial port through a USB-to-UART module, you can run the following command to start recording the signal into a wave file:
cargo run --release -- read-wav --port /dev/tty<UART-device> --sampling-rate X --baud-rate Y --output output.wavMake sure the --baud-rate and the --sampling-rate parameters are
in sync with the ones configured in the ESP32. Otherwise the program
won't be to read properly data from the ESP32 and keep it in sync with
the time in the wave file.
The application also integrates with PulseAudio so signal data can be continously sent to PulseAudio that can be recorded by normal applications, like Audacity. For that, the application will create a temporal null sink while it is running and will stream data to it. While the application is running, other applications will be able to read this data from the monitor of that sink. The application will destroy the sink once it terminates.
The command is the following:
cargo run --release -- pulse-stream --port /dev/tty<UART-device> --sampling-rate X --baud-rate Y --output output.wav