A $5 (€5) Raspberry Pi Pico 2 can now pull duty as a fully featured audio DSP, thanks to an open-source firmware called DSPi. Built by Weeb Labs, the firmware runs on both the RP2040 and RP2350 and presents itself to the host as a standard USB sound card, making it plug-and-play on Linux, macOS, Windows, and iOS. Once flashed, the Pico gains parametric EQ with up to 10 bands per channel, active crossovers up to 8th order (Linkwitz-Riley, Butterworth, and Bessel), room correction, time alignment, headphone crossfeed, loudness compensation based on ISO 226:2003, and a dedicated mono PDM subwoofer output that skips the need for a second DAC.
The RP2350-based Pico 2 has a clear edge over the original RP2040 Pico for DSP work. Its hardware FPU enables single-precision floating-point math with a hybrid SVF/biquad EQ architecture, while the RP2040 relies on hand-optimized ARM assembly running Q28 fixed-point. Both variants overclock their dual cores to 307.2 MHz, but the RP2350 doubles the output capacity: 4 stereo S/PDIF or I2S output slots (8 channels) versus 2 slots (4 channels), 110 total EQ filter bands versus 70, and an 11-channel signal path versus 7. USB audio input supports 16-bit and 24-bit PCM at 44.1, 48, and 96 kHz, with S/PDIF input available at 44.1 or 48 kHz.
Recent firmware updates have pushed DSPi well beyond basic room correction. Version 1.1.6 added a tube modeller that lets each output emulate one of 16 vacuum tube profiles with adjustable drive and mix, including transformer-speaker interaction modeling. Every output now also gets its own brickwall peak limiter with configurable threshold and release, and outputs can be linked into groups to keep settings synchronized. The firmware ships with a 10-slot preset system, per-channel diagnostics including peak/clip metering and CPU load reporting, and over-USB firmware updates that bypass the physical BOOTSEL button.
Weeb Labs provides two cross-platform companion tools for configuring the DSP. DSPi Console is a GUI application with real-time filter visualization and device monitoring, available for macOS, Windows, and Linux. The dedicated Linux build reached its first release, v1.1.6-beta4, on October 5, 2026, shipping as a 64-bit x86 binary that runs under both X11 and Wayland and bringing the Linux app to feature parity with the macOS version for firmware 1.1.6. For terminal-oriented workflows, DSPi Terminal offers the same capabilities from the command line through a full-screen TUI plus a scriptable CLI mode. On Linux, getting the USB sound card to show up without root access takes a one-time step: running sudo dspi --install-udev (or adding a udev rule by hand for the device's vendor and product IDs) and replugging the board. The firmware's open-source license has also drawn independent tooling from the community, including dspictl, a Go-based command-line client, a browser-based console, and a hardware fork, DSPi-ES9081, adapted for ES9081 DAC-based boards. The project has picked up over 1,200 GitHub stars and generated a 121-page discussion thread on Audio Science Review since its February 2026 introduction. All source code is available on Weeb Labs' GitHub, including ports for STM32 and an ESP32-S3 front panel.
