Open-source USB interface: Audio Widget
Announcement: Audio Widget project
The Audio Widget project is open-source code and schematics for
USB based digital audio. It has functional firmware and software. And
it sounds good!
Cool? You bet! Here you can get started with USB audio without
worrying too much about the USB part of things.
Or you can contribute to a great open-source coding project. The
most important contribution we could need right now is coders for
USB Audio Class 2 drivers on Windows. But other efforts are needed
too. See below.
The code is written in C for the Atmel AT32UC3A3256 32-bit MCU. It
supports USB Audio Class 1.0 and 2.0 (UAC2). On Windows / UAC1 it
works with 24/44.1 and 24/48 with sample skip/insert. Asynchronous
USB is in progress, and we could use your help.
On Linux (>2.6.37) and OS X, using asynchronous USB, it also
supports 24/88.2, 24/96, 24/176.4 and 24/192. The open-source
firmware is in a git repository. It can be selectively compiled to run
on the three different boards. The firmware includes several UI and
There are three hardware options. The hardware is in a beta state. It
plays music very well, but there is still tweak potential.
1) A stand-alone USB-DAC with stereo audio playback functions only.
This board uses the ES9022 DAC chip. Contact
george.boudreau@YoyodyneConsulting.ca for info on how to obtain
one. More information on the this and other audio designs visit
Yoyodyne Consulting/Audio Hardware
2) USB-I2S module + Analog Board. The module has all the pinouts you
need for digital audio, GPIO, I2C, SPI, LCD display and UART debug.
The module uses 2.0mm pitch pin rows. The Analog Board uses the
module to do stereo playback with an ES9022 DAC and low-noise
VBUS-LDO based power. AB-1 is a straightforward design to begin with,
and if you're into analog tweaking we challenge you to make your own
versions! Schematics and BOM are on
Downloads - sdr-widget - Audio and Control Interface for Amateur Radio SDR and Audiophile USB-DAC - Google Project Hosting.
Go to Q N K T C USB-I2S Module and Analog Board 1 for more information. Contact
email@example.com to obtain a kit.
3) SDR-Widget Beta 2.0. This is the original fork of the project,
open-source HAM radio. The hardware supports both playback and
record. Contact george.boudreau@YoyodyneConsultingl.com for info
on how to obtain one. Visit
for more information of pricing and availability.
For more information, go to sdr-widget - Audio and Control Interface for Amateur Radio SDR and Audiophile USB-DAC - Google Project Hosting
This announcement is cross-posted. Please join the mailing lists of
both SDR-Widget and Audio-Widget to continue the discussion there.
SDR-Widget is the original branch, where most of the firmware
discussions take place.
Feel like contributing? We'd always like to see more hands. There's
quite a few tasks planned:
- Firmware for Asynchronous UAC1 / Windows for 44.1 and 48ksps.
- Analog tweaks. Ideas are welcome for PSU, DAC, IVC, preamp etc.
Feel free to make suggestions, or even better, your own Analog
Board for the USB-I2S module.
- Windows open-source drivers for USB Audio Class 2.0. This
protocol is supported in Linux and OS X kernels, but not yet
- Adding more IO control to the firmware
nice.. this is really interesting... thanks..
Very cool, and thanks for sharing!
Very interesting project indeed.
I will certainly be following the progress.
Thanks! We think it's cool too! We're trying to make it a bit easier so that analog tweakers don't need to implement the entire digital chain.
Over at avrfreaks we're telling the coders they can program on an analog board which works.
I hope you can keep the audience over here updated with your project. At present there are very few ways to get a USB audio class 2 interface and none for the amateur. What are the licensing terms? Could an enterprising mfr. build boards to offer to the DIY market?
Honestly, I am not sure how this works with schematics and layouts.
Perhaps someone can elaborate?
Schematics and firmware source links can be found in the original announcement. There are 2 style of boards available. Pick the one you like and contact the author.
GPL does not deal with hardware, only software. However the group considers the schematics to be open source and you are free to take a hammer and chisel and carve out a board, for personal use, if you wish. Take my word you will create plenty of scrap before you get it right.
I have a few blank boards available for those with decent parts bin and a steady hand for soldering. Beware: there are 0603 size parts on the board and a 144pin LQFP processor. I am old enough to remember mono turntables with change for a dollar on the tone arm and I was able to assemble my board :)
George and I are the project's hardware designers. George has made available a stand-alone, unassembled DAC board.
Based on an earlier design (SDR-Widget) by George I have made a USB-I2S module with audio and debug IO. The module mates with an Analog Board. You're encouraged to make an AB of your own design. Module and AB-1 are assembled and audio-tested. See: Q N K T C USB-I2S Module and Analog Board 1
To buy kits, please send a message to George or myself depending on which version you need. The same goes if you're interested in licensing the layout.
Thanks for the details. I have been following the Google Group stuff but I thought this forum needed a better look into the device.
Looking at the other forum I'm a little confused about part of the specs so a few answers here will help.
1) Will it will automatically select the correct sample rate when selected from the source for the 6 standard sample rates with two oscillators (22.5792 MHz and 24.576 MHz)?
2) Does the same firmware work in both OSX and Linux? Can UAC 1 and UAC 2 support work in a single firmware?
I'll contact directly about commercial implementations.
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