Duncan McIntyre's BassMate Is a Smart STM32-Powered Drum Machine and Sequencer
Building on an earlier, Teensy 4.1-based design, this compact sequencer includes a smart user interface and Adafruit Trellis controls.
Maker Duncan McIntyre has put together a drum machine and sequencer, complete with blinky lights and an on-board display: the BassMate.
"I want to be able to quickly create simple rhythm sequences to help me practice electric bass, and was looking for something between a basic metronome and a full-fledged DAW [Digital Audio Workstation]," McIntyre explains of the project's origins. "The Drumbit online app is pretty good, but having to point and click while playing an instrument is not tactile enough for me."
McIntyre's first prototype was dubbed the BassedMate, and used a Teensy 4.1 microcontroller and a VLSI VS1053 digital signal processor (DSP) for MIDI communication. The project underwent a series of revisions before being abandoned earlier this year in favor of a redesign — which would become the BassMate.
"I wanted to eliminate the VS1053 chip and I found the Electrosmith Daisy Seed which looked like it could do all the synthesis itself. I also found the MusicBoard project which inspired me to try to port to the Seed," McIntyre explains. "This proved to be tricky, so I gave up (I'll try again one day!) and took a different path."
That path results in the finished BassMate: an STMicroelectronics STM32F411 Black Pill microcontroller, a return to the VS1053, and a Duppa NavKey to drive a revised user interface based around McIntyre's SimpleGUI library. Above the screen are, of course, a series of buttons that light up when pressed — courtesy of an Adafruit NeoTrellis — and trigger playback, or otherwise, of the sequencer's patterns.
Elsewhere inside the 3D-printed chassis are a pair of rotary encoders, an amplifier module, a display for the new UI, and a loudspeaker for stand-alone use. There's also a clever hack for the relatively unpleasant 0.5dB stepping of the VS1053's built-in volume control: an Analog Devices AD5204 digital potentiometer, allowing for smooth changes in volume.
Design files and source code for the BassMate are available on McIntyre's GitHub repository under the permissive Apache 2.0 license.