Is your question not already answered by the statement from the owner of this project? "**Everyone is free to work on this project.** **Firmware is not distributed freely. Only completed project is offered.** For contact: [trayko67@gmail.com](mailto:trayko67@gmail.com)" at: [https://oshwlab.com/trayko67/21-bands-spectrum-analyzer-buttoncontrol-ircontrol-v-1-0](https://oshwlab.com/trayko67/21-bands-spectrum-analyzer-buttoncontrol-ircontrol-v-1-0)<br> <br> This may be of some help: [https://blog.yavilevich.com/2016/08/arduino-sound-level-meter-and-spectrum-analyzer/](https://blog.yavilevich.com/2016/08/arduino-sound-level-meter-and-spectrum-analyzer/)

Never mind .. seems that NANO ESP32 / can get the job just fine, less expensive and more memory for less money ..