A Synthesizer SAO For the Supercon 2025 Badge

Hackaday Supercon has some of the best badges in the entire maker/hacker scene and 2025’s badge maintained that legacy. It was basically a handheld computer built around an ESP32-S3 and Seeed Studio’s Wio-SX1262 LoRa transceiver module. And, of course, it had the all-important SAO (Standard Add-On) port. Justin Miller took advantage of that port to turn his Supercon 2025 badge into a synthesizer.

The hardware for this synthesizer is about as simple as it could possibly be. It is literally just a single component: a piezo buzzer. One leg goes into GPIO Pin 1 on the SAO and the other leg goes into the ground pin. That might just make this the SAO with the shortest BoM in history—at the very least, it has to be tied for first place.

Because the hardware is so unbelievably basic, the synthesizer functionality all comes down to the software. Miller programmed that in MicroPython, which is what the Supercon 2025 badge was designed for. It outputs a PWM signal on Pin 1 with a frequency that matches the selected note. He then created a nice GUI using LVGL. That shows piano keys with labels for the corresponding keyboard buttons. The user gets those keys, plus the option to switch between octaves.

The Synthy Add-On was such at hit at Supercon 2025 that Miller was invited to the stage to give a live demonstration. If you have the badge and a piezo buzzer laying around, you can try it for yourself by grabbing the Python code from Miller’s GitHub repository.