Re: [Discuss-gnuradio] USRP2 FPGA Notes

[Matt Ettus]

David,

I understand your frustration.  Please understand that this decision was 
not made lightly.  We started out with the Spartan 3-1500 which is the 
largest chip supported by the free tools.  As we progressed, it became 
apparent that there was not enough Block RAM to cram in all firmware for 
the functionality we wanted at the same time.

I have some comments on your comments below, plus another possible 
solution at the end....

David M. Witten II wrote:
> > - Just use the prebuilt FPGA images we provide
> To what end?  Just to duplicate the efforts of others?

You should note that the vast majority of users of the original USRP 
never needed to use anything other than the standard FPGA build which we 
provided, and we anticipate that will be the case with the USRP2.  
Remember, the easiest place to do all of your processing is in the host 
computer, and we provide standard images which will allow you to do 
that.  Even the guys who built that complete GSM basestation out of a 
USRP1 used the standard FPGA build.  Also note that you can still write 
your own firmware for the processor in the FPGA, you just couldn't 
change logic around.

> > - Get a 60 day demo version from the Xilinx Web Site
> 60 days to conceive, implement, and debug - it can take 60 days to get 
> tools of this scale installed correctly.

I believe that you can get a new license repeatedly, so you could 
"renew" every 60 days without reinstalling the tools.  I realize that 
this is not optimal.

> > - Release your changes to the community and we can find some sort of 
> way
> > to build them for you (if anybody wants to work on putting together 
> some
> > scripts to do this automatically, let me know).
> An appealing idea, and it fits the community model well, but even if 
> it doesn't get the wind up the skirts of the legal types at Xylinx to 
> have their tools used in this way, I find it difficult to imagine how 
> this would not be cumbersome to the point of unusability.
>
> Still hoping for an alternative...

Well here is one alternative.  The S3-1500 is pin compatible with the 
2000.  If enough people wish to purchase a special version with the 
smaller FPGA I can have a number of them built that way.  You would have 
to do some work to save a few block RAMs, but this isn't impossible.  My 
last version that used the 1500 (rev 1) should still be in the repository.


Please let me know what you think.

Matt