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Weeb Labs
Free · Open sourceRP2040RP2350

DSPi

Packing some of the industry's most expensive functionality into a $1 microcontroller.

110
filter bands

across all channels on RP2350

DSPi transforms a Raspberry Pi Pico or any other RP2040 or RP2350 board into a very competent and inexpensive little digital audio processor. It appears to your computer as a class-compliant USB sound card, with no drivers to install on macOS, Windows, Linux or iOS. Everything that leaves it has been through a genuine DSP pipeline first.

The signal chain runs per-channel preamp, matrix mixer, parametric EQ, crossovers, loudness compensation, crossfeed, volume levelling, time alignment and master volume, split across both cores for throughput. Outputs go out as S/PDIF or I2S on up to four independent stereo slots, plus a dedicated mono PDM subwoofer channel, so you can drive a multi-way active speaker without a second DAC.

It is my hope that the RP2040 and RP2350 will earn a reputation as the swiss army knife of audio for less than the price of a cup of coffee. DSPi is the argument for that.

Highlights

  • 10 PEQ bands per channel, 11 filter types, 110 total bands on RP2350
  • Linkwitz-Riley, Butterworth and Bessel crossovers to 48 dB/oct
  • Four stereo output slots, switchable between S/PDIF and I2S at runtime
  • Mono PDM subwoofer output with a 2nd-order delta-sigma modulator
  • ISO 226:2003 loudness compensation and BS2B headphone crossfeed
  • 10 preset slots with names, plus fully reassignable output GPIOs

Specifications

USB input
16/24-bit PCM · 44.1 / 48 / 96 kHz
S/PDIF input
24-bit stereo · 44.1 / 48 kHz · LG SoundSync decoded
Outputs
8 ch on RP2350, 4 ch on RP2040 · S/PDIF or I2S per slot
Matrix mixer
2×9 on RP2350, 2×5 on RP2040 · gain + phase per crosspoint
EQ
Up to 10 bands/channel · hybrid SVF+biquad on RP2350
Crossovers
4 per output channel · LR / Butterworth / Bessel · to 8th order
Time alignment
Per-output delay to 85 ms, path latency auto-compensated
Presets
10 slots, named, with a configurable startup slot
Host support
macOS, Windows, Linux, iOS · class compliant
License
Open source

From the dev log

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