SDR Widget Project

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(Page last updated 2011-04-17... text and pictures)

SDR-Widget: What is it?

A full fledged sound card with superior performance compared with all audio cards we have tested, in addition to the Mobo style SDR control functions.

The SDR-Widget is an attempt to create an SDR (software defined radio)  focused audio/control card. The design is based on the AK5394A 24bit ADC and the Atmel AT32UC3A3256 processor.  If used with the Mobo project, it replaces the on-board controller on the Mobo and it replaces the external audio cards used with the Mobo, there will only be one connection between the SDR and the Computer, the USB connection, carrying both control and audio.  

My own contribution to this project is mainly to bash together the code (firmware) required to support the Mobo functions (see Mobo 4.3 project).  Mobo functions include Si570 frequency control, TX/RX and BPF+LPF switching, TX PA bias management, Power/SWR meter, high SWR protect, Temperature shutdown and cooling fan control, Rotary Encoder VFO... In addition there are also Rotary Encoder driven Menu functions. The Mobo functions are already about 99% done (some debugging left) and fill probably close to 5000 lines of code in total, while the Menu functionality which is coded in fat, fast, repetitive and ugly style, is already over 3000 lines.

A much more refined code development however is needed to support the composite high speed USB device and the super low noise/low jitter 24 bit 48 - 192kHz ADC/DAC functions.  To date this development has mainly been in the capable hands of Alex Lee, 9V1AL and Ken, WA2VFN.  Hardware, including PCB and kit development, not to forget setting up the initial software framework, all courtesy of George Boudreau.

One of the problems with coding for the Widget is the myriad of possibilities necessitating a multitude of diverging functional branches of the firmware.  Roger Critchlow, AD5DZ, has performed quite a feat in unifying all those branches again, including all the features in a menu like selection system.

Now that I have started calling out some names, please note:  The SDR-Widget is an open group project with a large support base and a growing number of active contributors.  

These links contain all further description and the latest snapshots of the software development:


The Alpha version of the SDR-Widget-lite already outperforms all commercial USB sounds cards that we have been able to compare with. The frequency response is practically flat to 96kHz. The noise floor is at approximately -157dBfc/Hz.  This may even improve further as the project progresses.  See this test report:


All further information can be found at the links indicated above.

Below are pictures of the various hardware builds of the SDR Widget and the Audio Widget:

SDR Widgets:

All these were assembled the hard way, soldering iron and solder paste + heat gun.

The very first build of the Alpha1 version of the CPU board.  Still pretty much brain dead.  
The 144 pin CPU slug was much fun to solder in place:

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The fully assembled Alpha1 version.  Already a superb performer,
except for low frequency rumble at up to -70dBc when using USB power:

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Alpha2 version, CPU board, top.  Two of these were built.  
The Alpha2+ version also incorporates a DAC on the PCB:

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Alpha2 version, CPU board, bottom... things are getting more complex:

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Alpha2+ version, CPU board, top.  The CS4344 24bit DAC is in place, see top middle:

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Alpha2+ version, CPU board, bottom:

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Alpha2 (and Alpha2+) version, ADC board, top:

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Alpha 2 (and Alpha2+) ADC board, bottom:

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Alpha2 version up and running with an early version of the firmware (no input is connected).
Current firmware and hardware shows a much lower noise level than indicated on the display.

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This picture shows the ADC reference Caps replaced with very large value capacitors.  
This improved the overall performance by a marginal amount of 1dB.

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The Beta/Final version, no cuts or jumpers anymore.  The bottom board, forgot to take a picture,
is the same as the one above, except for improved placement of the four large capacitors:

(click on picture to enlarge)

Audio Widgets:

AB-1 Version of Audio Widget (design by Børge Strand-Bergersen).  
Playback only, using the ESS ES9022 DAC.  My AB-1 is
built into a Hammond box and includes a 20x4 LCD for VU meters.
Here shown driving my brand new and fiendishly expensive headphones,
HiFi comes at a price:

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Audio Widget (design by George Boudreau).  A more economical design, not
intended for potential future drop-in additions.  Uses the ES9023 DAC and a SiLabs
Si532 dual rate oscillator as a DAC clock.  Same functionality and performance 
as the AB-1 Widget.
I figure this is the seventh 144 pin AT32UC3A3256 CPU that I solder onto a PCB.
Quite a Zen-like experience.  Have ordered an aluminum enclosure, but it hasn't arrived yet:

(click on picture to enlarge)

My Widget enabled HF Transceiver:

Well, the Widget started as a Amateur Radio Project.  Here is my first proud build
of a fully functional 4 Watt All Band (160 - 10m) HF Transceiver using the Widget for baseband (audio) processing,
frequency control, BPF/LPF control and all other transceiver management, including Power/SWR
metering, hi-SWR sensing, bias management, thermal management etc...:

Other building blocks in this transceiver are:  
  • Mobo 4.3 (described here), not using the built-in controller which is now replaced by the SDR-Widget;
  • LPF filters (LPF-100, see HF SuperPacker Pro kit, no affiliation) and a PCF8574 I/O board to control it;
  • Power/SWR sensor;
  • LCD, rotary encoder and a pushbutton switch for frequency tune and management; and
  • USB connectivity to PC computer running SDR Software, includes audio in/out and control 

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