thanks Johnathan and Eric, I'm glad I asked before spending too much time trying to make this work! :-)
Johnathan, the custom FPGA firmware you describe sounds like it might be perfect for what we want to do, provided it's not impossible to demux the data stream. I haven't seen any usrp2 FPGA sources (they don't appear to be in either the 3.2.2 or 3.3.3 tarballs) - I guess this means I need to figure out the new "git" stuff... it sounds like I will need to get a Xilinx compiler to build them, once I find them. On Wed, Jan 27, 2010 at 1:23 PM, Johnathan Corgan <jcor...@corganenterprises.com> wrote: > On Wed, Jan 27, 2010 at 10:05, Eric Blossom <e...@comsec.com> wrote: > >> See comment above about there currently being only a single DDC in the >> FPGA. If you want two channels, amongst other things, you'll need to >> instantiate two DDCs, and add code that interleaves the samples from >> the two DDCs. You'll also have to create host and firmware that can >> select the 1 or 2 channel case. > > There is a custom USRP2 top-level FPGA build that creates two > synchronous DDCs (they share a CORDIC NCO phase accumulator) in the > usrp2/fpga/top/u2_rev3_2rx_iad directory. It is designed to > synchronously sample the two inputs of a BasicRX or LFRX as separate > real signals. > > (It also implements an integrate-and-dump decimator instead of the CIC > and HB, for unrelated reasons.) > > The complex outputs of the two DDCs are interleaved and placed into a > single data stream, are started and stopped at the same time, and > share a common frequency and decimation rate. Thus, the host and > firmware code are unchanged. If this serves your purpose, it would be > a good place to start. It does sound like, though, from your original > post, that you are looking to have independent streams, and the above > won't help you. > > Johnathan > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
