[Igor b] plays in a band and wanted a way to use a foot pedal to trigger samples. Since he had a STM32F429 evaluation board handy, he decided to build the Stmpler using the board, a touch screen, an SD card, and not much else.
To save pins, [Igor] used SPI mode (instead of SDIO) to access the SD card. He generates audio output using filtered PWM to keep the design simple. Because of the PWM, there is a compromise between bit depth and sampling rate, and [Igor] settled on 12 bit samples at 20.5 kHz.
The software uses Chibios/RT for an RTOS and a GUI library to manage the touch screen. [Igor] says he still has features to add, but that he’s already using it in his performances. The filtered PWM may not be exactly hi-fidelity, but it probably sounds better than a 3D printer. Or maybe he’ll take a tip from us and go wireless.