ESP32 Digitally Controlled Oscillator

Introduction

This software produces a square wave on a specified GPIO at the requested frequency.

This component can use the RMT peripheral or the LED_PWM peripheral to accurately generate the signal.

The RMT approach works quite well, and can generate frequencies up to tens of megahertz, however it is complex to configure.

The LCD_PWM approach is much simpler to configure, however it seems limited to frequencies from about 10 - 10,000 Hz. I have also had trouble getting the low-speed timers to work with the LED_PWM.

Duty cycle can be configured with the LED_PWM approach.

Choose your method in app_main.c.

It is written and tested for v3.3 of the ESP-IDF environment, using the xtensa-esp32-elf toolchain (gcc version 5.2.0).

Ensure that submodules are cloned:

$ git clone --recursive https://github.com/DavidAntliff/esp32-dco.git

Build the application with:

$ cd esp32-dco
$ idf.py menuconfig
$ idf.py build
$ idf.py -p (PORT) flash monitor

Source Code

The source is available from GitHub.

License

The code in this project is licensed under the MIT license - see LICENSE for details.

Roadmap

• Runtime determination of optimal clock divider with RMT approach.
• Select duty cycle with RMT approach.
• Support for runtime variation of frequency, possibly via MQTT command.
• Support for phase inversion.
• Support for multiple channels and phase shifting between channels.
• Investigate low-speed timer problems with LED_PWM approach.
• Support for Build System selection of DCO method.