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Re: [Xylo-SDR] Firewire, DSP and FPGA on one module
Robert,
I may have read a lot into the project that I wanted to see but I
thought one of the reasons for the efforts were to replace the desktop /
laptop. This thought may apply to the disscussion of the USB 1 or 2.0,
it is a link to the desktop / laptop and we know that can be done, but
in order to have a SDR free from the big computer we need hardware that
is fieldable and relatively low power.
Cash
-----Original Message-----
From: xylo-sdr-bounces@lists.ae5k.us
[mailto:xylo-sdr-bounces@lists.ae5k.us] On Behalf Of Robert McGwier
Sent: Sunday, December 18, 2005 4:31 AM
To: Xylo-SDR Discussion
Subject: Re: [Xylo-SDR] Firewire, DSP and FPGA on one module
Hello Leon!
The 16 bit fixed point DSP chip could be an issue which is dependent on
how it is used. Dealing with fixed point is an art few can master. I
did it with the AEA DSP boxes 15 years ago because there was no other
choice and I am doing it now in FPGA and some smaller spacecraft
embedded microsystems. I am uncertain about its suitability for general
experimentation with the goal of a high performance SDR. If it were a
32 bit fixed point system, we would be in business. The FPGA seems
nice enough. The USRP uses Cyclone with 20,000-ish logical elements.
This has 50K. So that is a win plus it has the 18x18 multipliers. All
positives. It is my personal opinion that we are better served at this
time by mostly avoiding the use of DSP chips, especially fixed point
ones and to rely on our ability to speedily process data on our modern
desktops. The SDR-1000 DSP core, written by AB2KT and I, recently was
hung on the end of an Agilent multi receiver system. It successfully
prosecuted 92 separate receivers, each sending I/Q at 8000 samples per
second, simultaneously on a 2.4 GHz Xeon based Dell Server. The
processor was not sweating at all. It will easily do this up to 48000
samples per second since we were not consuming 1/6 of the CPU resources.
I went to Reno to work with the Gnu Radio folks for a week. Using the
GnuRadio software elements, plus some blocks I helped write, we
implemented a 1 Mbps GMSK packet SYSTEM that transfers data over USB
2.0 (the preferred medium unless you can demonstrate WHY you must have
firewire) and we did it from scratch in 3 days . You may download that
software now from GnuRadio. This ran successfully on the N2MJI (USRP
hardware designer) abacus, a 1.8 GHz celeron laptop. We do need to
stop underestimating these desktops and to learn how to optimize for
them because they are so much easier to deal with than DSP chips. DSP
chips are your last resort and intended primarily for embedded systems
that must have them. I would limit there use to those places where I
need a completely standalone device and could afford to hang an external
system on the SDR.
The nice thing about using the FX2 and USB 2.0, is that we can and
should adapt our toy to use the HUGE body of software that GnuRadio has
produced in addition to those things we can and should add.
73's
Bob
N4HY
Leon Heller wrote:
>Here is an interesting product with a TI DSP, Spartan 3 FPGA and
>Firewire:
>
>http://www.traquair.com/products/ultracompact/uc1394a-3.html
>
>Just add an ADC for a high-performance SDR!
>
>Leon
>--
>Leon Heller, G1HSM
>leon.heller@bulldoghome.com http://www.geocities.com/leon_heller
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--
Laziness is the number one inspiration for ingenuity. Guilty as
charged!
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