Raspberry Pi 5 Becomes an 8-Channel USB Sound Card With Optical Out

One Blinking GPIO Pin Just Became a Real Optical Audio Port

Every so often a maker project comes along that makes you sit up and say, "wait, you can do that?!" This is one of those. Developer Oliver, the mind behind RASPIAUDIO, has coaxed a Raspberry Pi 5 into behaving as a full ALSA-compatible, 8-channel USB audio interface, complete with genuine S/PDIF TOSLINK optical output. The best part, and the part that delights the hardware nerd in me, is that the optical signal is produced by simply blinking an LED off a single GPIO pin. No dedicated transmitter chip. Just light, timing, and a very clever idea.

The Trick Hiding Inside TOSLINK

TOSLINK feels exotic because it is optical, but underneath the mystique it is refreshingly simple. The old S/PDIF-over-fiber standard is essentially a fast on/off optical signal: light on, light off, encoded at a precise rate. If you can toggle a light source quickly and accurately enough, you are speaking TOSLINK. That is exactly what Oliver's setup does. A humble LED driven from one GPIO line becomes the optical transmitter, flashing out a bitstream that any home receiver or soundbar will happily decode as a legitimate digital audio input.

The catch, of course, is timing. Audio is unforgiving about jitter, and a general-purpose Linux box juggling dozens of tasks is not where you would normally expect rock-steady microsecond precision.

Why the Raspberry Pi 5 Makes This Work

Here is where the Raspberry Pi 5 earns its keep. The board's new RP1 I/O chip includes a programmable I/O (PIO) block, and that PIO handles the precise bit timing directly in hardware. Because the pin toggling is offloaded to dedicated silicon, ordinary Linux scheduling jitter never gets a chance to corrupt the stream. The operating system can hiccup all it likes; the PIO keeps clocking out clean bits. It is a beautiful example of using the right piece of hardware for a job that software alone would fumble.

The other half of the magic is the Pi's USB gadget mode. Instead of acting as a USB host, the Pi 5 presents itself to a connected PC as a standard, driver-free sound card. Plug it in and your computer simply sees eight channels of audio output waiting to be used, no exotic setup required. If you enjoy watching modern boards absorb jobs that once demanded dedicated gear, our ongoing coverage of single-board computer projects is full of exactly this kind of resourcefulness.

Open Source, Built on Camilla DSP

The whole configuration is built around Camilla DSP, the well-regarded open-source digital signal processing engine, and Oliver has published the project on GitHub for anyone to replicate or extend. That openness matters. It means hobbyists can route, mix, and filter those eight channels in software, then fan them out to analog, USB, or that GPIO-driven optical port however their listening room demands.

What I love most is the philosophy on display. A single-board computer that costs less than a night out is standing in for a rack of specialized audio hardware, and doing it with parts most tinkerers already own. As affordable boards keep swallowing tasks that used to need custom silicon, the same trend showing up across artificial intelligence and edge computing is playing out on the workbench: capable, flexible, and gloriously hackable.

If you have a spare Pi 5 and a length of fiber, this is a weekend well spent. Blink a pin, pipe out eight channels, and marvel that light itself is carrying your music.

Sources: Hackaday, July 8, 2026; RASPIAUDIO / Camilla DSP GitHub, July 2026.