Ohmic's PICO DSP Is a One-Stop, Arduino-Compatible ESP32 Board for Digital Signal Processing

Built around an Espressif ESP32 PICO D4, the board comes with a choice of 4MB of flash and 8MB PSRAM or 16MB of flash.

Ohmic Electronics is crowdfunding an open source ESP32-based Arduino-compatible digital signal processing board for audio development, Andy Wilson's PICO DSP — promising an all-in-one design that doesn't take up too much desk space.

"PICO DSP is an open source, Arduino-compatible ESP32 development board for audio and digital signal processing (DSP) applications," designer Wilson explains of his creation. "It offers an expansive audio-processing feature set on a small-format, breadboard-friendly device that provides audio inputs, audio outputs, a low-noise microphone array, an integrated test-speaker option, additional memory, battery-charge management, and ESD protection all on one tiny PCB."

The PICO DSP looks to offer as many audio-related features as possible in a compact breadboard-friendly layout. (📹: Ohmic Electronics)

Wilson positions the board as suitable for a number of digital signal processing workloads in fields including music, art, creative technology, adaptive technology, and more - including voice-user-interface (VUI) projects, sensor networks, and digital music synthesis.

Built around an Espressif ESP32 PICO D4 processor, the board includes a 32-bit dual-core microcontroller running at 80/160/240MHz, either 4MB of SPI flash and 8MB of pseudostatic RAM (PSRAM) or 16MB of external SPI flash, 802.11b/g/n 2.4GHz Wi-Fi, Bluetooth Low Energy (BLE) 4.2, and an on-board antenna. The audio side is handled by a Wolfson WM9878 stereo audio codec with 3.5mm connectors for audio input and output plus stereo line in and mono audio out on the GPIO header, and two on-board Knowles MEMS microphones which can work as broadside or end-fire beam-forming arrays. An on-board 1W speaker driver is additionally broken out on the GPIO header.

This video shows the PICO DSP running a Faust DSP patch, to give an idea of the quality available. (📹: Ohmic Electronics)

The breadboard-friendly design includes 11 GPIO pins with access to both ESP32 analog-to-digital converter (ADC) channels, JTAG for debugging, and capacitive touch, and a USB Type-C connector for both data and power. Wilson rates the board at 100mA for normal use with Wi-Fi disabled and the mics active and under DSP control, 52.4mA with the audio codec in standby, and just 5.7mA with the ESP32 in its deep-sleep mode.

"PICO DSP is an open source project released under the CERN Open Hardware License v1.2. We believe strongly in the benefits of open source design, and if you are reading this, we hope you will contribute to the project," Wilson writes. "Our goal is to create a reliable development board for audio applications and to provide all of the necessary documentation for it. There are unexplored applications for this hardware, and we invite you to help us find them!"

Wilson's desire to do good extends beyond the world of open source, too. "We intend to make a contribution to MASI, the Movement of Asylum Seekers in Ireland, to support their work to end Direct Provision in Ireland," he adds of the plans for successful funding. "You can find out more about MASI’s work and support it via a direct donation at https://www.masi.ie."

Sample source code for the board is available on the company's GitHub repository, alongside a schematic, under the permissive MIT License; interested parties can back the project on Crowd Supply for $29 at early bird or $34 at standard pricing — with a Eurorack-compatible expansion board available at additional cost.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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