Re: [Discuss-gnuradio] reading two rx channels on usrp2

[Johnathan Corgan]

On Wed, Jan 27, 2010 at 10:05, Eric Blossom <address@hidden> 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