On 01/02/12 19:12, Attila Kinali wrote:
On Wed, 1 Feb 2012 09:27:30 -0800
Chris Albertson<[email protected]> wrote:
I thought it might be interresting but then found out you need to buy
$2,000+ worth of hardware for even start experimenting. Open Source
SDR needs to run on a common affordable platform or it will never gain
the critical mass of users that it take to make the project live
longer then a few months.
That's because the URSP is a general purpose system. It is designed
to do many things. That makes it expensive. And being expensive,
it has a low production volume, which makes it even more expensive.
I think, a specialized GPS SDR can be build for less than 500 USD
in low (a dozen at max) volumes.
I guestimate, that the RF/ADC part would cost somewhere between
100 to 200 USD in parts. The big uncertainty here is the FPGA.
I have no clue how much logic space for a GPS SDR would be needed
at minimum and how much would be desirable. Hence i have no guess
what the FPGA would cost (could be anything from a cheap 20USD
FPGA to a 300 USD one).
That's why you start of with using an Ettus box as a boiler plate. Once
you have working code, you can re-target it for a smaller device and
situation. You can do dry synthesis towards the new platform without
having it as a physical device. The basic design can still be running on
that Ettus platform. Come to think of it, I did get a few university
point on a 2-week coarse teaching exactly this point, spin on big-ass
FPGA machines and then go to target. :) That's... 18 years ago. Time flies.
I think the way to go is to find a commercial GPS chip that has a low
level interface and then build the uP controller using a common
development system. Both the chip and the uP board need to be,
common, well documented and cheap.
There are no common, well documented and cheap GPS frontend chips
out there. All chips that are still in production are for high volume
stuff. Without knowing someone inside those companies, you will not
be able to get them at single pieces. I searched quite a while some
time ago, and couldn't find anything that is not EOL. Finally i came
to the conclusion that it is easier to build a custom frontend from
scratch, from the available HF parts.
Front-end chips is still there. That's how they build these:
http://ccar.colorado.edu/gnss/
http://www.sparkfun.com/products/8238
http://www.sparkfun.com/products/10981
That will suffice to get you started in the SDR field.
Cheers,
Magnus
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