Sunday, December 26, 2010

PIC32MX? SDR-Cube Next step?

One of the things that fascinates me about the SDR-Cube project is that it is based on the Microchip 16-bit (fixed point) DSPic33.  I've done some work with the more powerful but in some packages pin compatible PIC32MX 32-bit processor.  It's too bad, actually, that George and Juha went with the easier to solder 0.5 mm pitch DSPic part as there is an exact pin compatible part in the 0.4mm package that, if it would have been used instead on the DSP board on the SDR-Cube could have been a drop in.  I would have likely bought a second DSP board to try it and do a relatively simple code port.

I'm thinking of adding some features and doing some customizations to the code... so I'm starting to set up the development environment here at home.

While looking around to get ready for the PIC work on my home computer.. I found this.

It is cheap.. apparently $99 plus $25 for shipping.  It's sexy... it has a stereo CODEC similar to the TI one on the SDR-Cube.

Front View:

Rear View:

There are also two other versions with more peripherals, the version with the PIC32MX7xx series part is especially interesting as it has the Ethernet interface and would be capable of TCP/IP...maybe even remoting given the PIC32MX is fast enough.  I don't know the answer to that at this time.. that board is $149+$25.

The only issue I see with these for a port of Juha's code is that the board uses the MONO MIC input on the board...  so to make this work with I&Q the stereo line inputs on the CODEC chip would have to be tack soldered to a small off board circuit (RC filter I'd guess)....at the least.  I suppose worst case you could run the TI CODEC in the board via SPI as well.  It looks like most of the I/O's from the PIC come off the board so it would be easy to add off board I/O cards and peripherals.

It's a thought for after the initial project is working.  A learning opportunity maybe.  The graphics library port would be.. interesting.. at least...

On the message board of this manufacturer, they stated that the PIC32MX Graphic board is exactly 2x as fast as their (and they do have one) version of this board that runs on the DSPic33.  In addition, the 32-bit processor would likely perform all of the math in (fixed point) 32-bits.. meaning that the full 24-bits of the CODEC likely could be manipulated.  It's an interesting thought.

In the future, though.. I'm wondering if a board like a Beagle board running on a dedicated processor would not even be a better way of doing this, or an ARM or a TI DSP.  But this is all about the design criteria.  The SDR-Cube the way it is more likely to be a better unit for small QRP portable battery operation than a  board like this or especially an ARM or Beagle Board would be because the current draw of the unit is very low for what it is doing.  This would be somewhat lost with a full color TFT and a 2x faster clock rate and MIPS core in the PIC32MX.

I'm more interested in the more computing power options, but many of the QRPers and SDR-Cube is not.

What I really like about the SDR-Cube project is the Code that Juha has written.  I'm just guessing now about another path that this code can easily be ported to provide.

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