Re: [Discuss-gnuradio] Gigabit Design Proposal

[Darrell Harmon]

David Carr wrote:

> Hi all,
>
> I've been working on a gigabit software radio peripheral design
> proposal.  Its a very early and easy to change document.  From doing the
> early design work, I can say that this is a big undertaking.  I think
> that the more people we can get interested the more possible it is. 
> Take a look:
> http://oscar.dcarr.org/ssrp/hardware/gitd-design.pdf
>
> Thanks,
> David Carr
>
>
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>
>
>  
I have read the proposal and it all sounds good.  You may want to 
consider going BGA for the FPGA.  Signal integrity with the DDR SDRAM 
may become an issue.  Also note that all the VREF pins will be lost as 
IO on banks with the SSTL2 IO.  The SSO (simultaneously swithching 
output) data for the QFPs in the Spartan 3 datasheet is depressing.

I decided not to build the DSP only SDR with no FPGA, but am now 
planning to build a more modular system.  I posted some details at 
http://dlharmon.com/dspcard/adcdac.html  The motherboard will contain 
ADCs and DACs.  A daugterboard will contain the FPGA and interface.  I 
would say the motherboard prototype is a month or two out.  I am also 
providing an additional daughterboard connector with approximately 20 
(or 34 with no second DAC) digital IO which is intended for an 
alternative interface such as RGMII to a PHY.

I have completed the design of the FPGA/DSP/USB board and have a bare 
board sitting here on my desk waiting for parts.  I did use a BGA FPGA 
(XC3S1000 FT256) and am going to attempt soldering it in a toaster 
oven.  If that fails I will send the other board to an assembly house 
and have it done ($50).  I just put up a webpage on it at 
http://dlharmon.com/dspcard/index.html  Approximately 80 FPGA IO are 
available in a 0.5mm pitch header.  29 will be used for ADCs, 29 for 
DACs, and the remaining IO will go to the digital daughterboard.  I 
could drop a DAC for more digital IO.

I would be interested in working with you on this, but obviously I have 
my own thing going.  It is a huge undertaking and is probably too much 
for me.  I already have the FPGA board taken care of (hopefully).  We 
could work together on the motherboard, and do a gig ethernet 
daughterboard.  The information I have posted is just based on my 
sketches and I am open to making it different.  Even if you are not 
interested in working with me using the DSPCARD, I would be happy to 
look over schematics, give ideas and such.  I am more of a hardware 
hacker than a software hacker so I cannot assist much with the software 
side.

--
Darrell Harmon
http://dlharmon.com/