Re: [Discuss-gnuradio] USRP Memory

[Eric Blossom]

On Thu, Jan 05, 2006 at 11:22:19AM -0500, Elaine Garbarine wrote:
> Hello again,
> 
> Now that I finally have my GNU Radio installations working properly I've got
> some questions about the USRP that I'm hoping you guys could help me out
> with.  I want to develop a system using the USRP in conjunction with a DSP
> board to build a Software Defined Radio testbed.  I'm curious if the USRP
> has any sort of memory at all.  I need to be able to buffer at least one
> packet (not sure how big that will be just yet) while I do a bit of
> processing on the FPGA before farming the data out to my DSP for further
> processing.

The USRP has some memory.  It's in the ram blocks in the FPGA.  We're
currently using a little more than 50% of it, and it's almost all for
buffering packets on their way to/from the FX2.  Yes, it buffers more
than 1 (USB) packet.

> Also, could you guys tell me if it would be at all possible to modify the
> Verilog code such that it sends and receives data over a group of the GPIO
> pins accessible via the headers on the Daughterboards instead of sending the
> data out of the USB2.0 interface?

Yes.  It is possible.  It's a "Simple Matter of Programming (TM)"

The top level of the verilog source for the FPGA can be found here:

   usrp/fpga/toplevel/usrp_std/usrp_std.v

The bulk of the code is here:

   usrp/fpga/sdr_lib/*.v

> Many thanks for all of the help you guys have provided.

You're welcome!

> -Elaine Garbarine

Have fun!
Eric