Re: [Discuss-gnuradio] Frontend Hardware which is not USRP

[Eric Blossom]

On Mon, Dec 10, 2007 at 01:28:38PM -0800, Fasika Alemayehu wrote:
> Hi Eric,
> 
> I also have got a similar situation. We are building a software
> defined radio using GNU radio. We have a receiver front end to test
> and analyze the performance of Wireless sensor nodes at 2.5GHz. The
> module is similar with USRP but we are studying the differences
> inorder to integrate the hardware with the gnuradio. I would really
> appreciate if I can find any documentation about the details of the
> signal transfer to/from the usrp and the usrp itself so that we can
> see the difference between the USRP and our hardware.
> 
> Best ,
> Fasika 

There is no documentation outside of that in the code on this.

However, it's pretty straight-forward.  We talk to the USRP using 3
USB end points.  EP0, the control endpoint, is used to load FX2
firmware and the FPGA .rbf file, low-level control of the
daughterboards, setting control registers in the FPGA, and other misc
operations.  The list of operations and the arguments is in
usrp/firmware/include/usrp_commands.h

Received samples are sent from the FPGA via the FX2 over endpoint 6
using USB bulk transfers.  Each USB packet is 512 bytes long, and the
data in each packet is interleaved 16-bit little-endian I & Q pairs.
I.e.,  I0, Q0, I1, Q1,...

Transmit samples are sent in the same format over endpoint 2 using 
USB bulk tranfers.

The schematics of the USRP are available as PDFs and gscheme source
here: http://gnuradio.org/trac/browser/usrp-hw/trunk/USRP_REV_4_2

Eric