DSPi Firmware Turns a Raspberry Pi Pico Into a USB DSP Card

Room correction and active crossovers used to mean buying a dedicated audio processor. DSPi, an open-source firmware highlighted by CNX Software on October 7, 2026, turns a Raspberry Pi Pico or Pico 2 into a plug-and-play USB sound card with a full digital signal processing engine built in. For DIY audio fans, it is one of the most capable things you can do with a microcontroller board that costs a few dollars.

• Boards: Raspberry Pi Pico (RP2040) and Pico 2 (RP2350).
• Audio input: 16-bit or 24-bit PCM over USB at 44.1, 48 or 96kHz, plus optional S/PDIF input.
• Outputs: S/PDIF, I2S and PDM, with 2 stereo output slots on RP2040 and 4 on RP2350.
• DSP: up to 10 parametric EQ bands per channel, for 70 bands on RP2040 and 110 on RP2350.

What Can the DSPi Firmware Do?

DSPi shows up as a standard USB audio device on macOS, Windows, Linux and iOS, so there are no drivers to install. Once audio arrives, the firmware applies a full chain of processing before sending it to your amplifier or DAC.

Highlights from the CNX write-up include:

• Room correction and parametric EQ to tame boomy bass or harsh treble.
• Active crossovers up to 8th order, so you can split frequencies between woofers, tweeters and a subwoofer.
• Time alignment with up to 85ms of delay, to line up drivers that sit at different distances.
• Loudness compensation based on the ISO 226:2003 standard, which keeps quiet listening sounding full.

RP2040 or RP2350: Which Pico Should You Use?

Both work, but the Pico 2 is the stronger choice. On the RP2040, DSPi handles 7 channels and does its maths with hand-tuned ARM assembly. The RP2350 adds a hardware floating-point unit, which lifts the limit to 11 channels and 110 EQ bands. If you are planning a multi-way speaker build or a stereo setup with a subwoofer, that extra headroom is worth the small price difference.

How Do You Control DSPi?

The project includes DSPi Console, a graphical app for macOS, Windows and Linux with real-time control and filter visualization, plus DSPi Terminal for people who prefer the command line. The code is on GitHub, where it has built a sizable following. CNX notes that developer Weeb Labs built the project with help from Anthropic's Claude.

If you prefer a full computer in the audio chain, our look at a Raspberry Pi 5 USB sound card with optical output covers a different approach. For more microcontroller builds, browse our mini computers section.

Sources: CNX Software — October 7, 2026; GitHub: WeebLabs/DSPi.