Every Raspberry Pi I own boots into a whole Linux distro before it does anything, which felt like overkill for the one thing I actually wanted: something that makes a sound the moment it’s powered on. StupidSynth throws out the OS entirely — it runs bare-metal on an original Raspberry Pi 1 (or Zero), boots straight into the synth code in one to two seconds, and starts playing.
Once it boots there’s nothing to configure and nothing to press. It just loops a randomly generated melody as a single-voice sawtooth wave out the 3.5mm jack, while the composite video output draws a bare red bar that pulses with the amplitude. No filesystem, no drivers beyond what the synth itself needs, no input handling at all.
The actual interesting part is everything that has to happen before “Hello, World” even makes sense on hardware like this. There’s no libc, no OS, so kernel.c has to be the entire universe — audio generation, video timing, and a boot stub in assembly that hands control over from the Pi’s own firmware in the first place, all built with a bare gcc-arm-none-eabi cross-compiler and linked against a custom linker script. Getting the deploy loop fast enough to be worth iterating on mattered more here than usual, so there’s a Distrobox-based dev container and a script that finds the SD card, copies the built kernel and firmware onto it, and unmounts it — no manual dd-ing required.
This one’s deliberately small and dumb, hence the name, and it only runs on the original BCM2835-based boards (Pi 1, Zero, Zero W), not anything newer. Full source, the deploy scripts, and manual setup instructions are in the StupidSynth repository.