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Re: [Xylo-SDR] Firewire, DSP and FPGA on one module



Folks

Sorry left out the link:

http://www.beyondlogic.org/usb/usbhard2.htm

Eric


-----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 6:31 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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