[USRP-users] Using multiple RX DDC chains on USRP2

Josh Blum josh at ettus.com
Thu Feb 7 16:17:27 EST 2013

On 02/07/2013 02:49 PM, Roy Thompson wrote:
> I am starting to look through some of the FPGA code for the USRP2 and
> I noticed that there are 2 RX DDC chains.  I would like to be able to
> use one of the chains to do standard DDC processing, and I would like
> to modify the second chain to do custom processing on the same A/D
> channel.  The output sample rate for the second chain will be
> different from the first. Is it possible to configure the UHD driver
> to support this configuration and allow for receiving from both
> chains?

The rx_multi_samples example can show you how to use two DDC chains. If
you had a WBX for example with frontend (named 0), this would map
frontend 0 located on the first and only daughterboard (named A) to DSP0
and DSP1 --subdev="A:0 A:0"

see the --help for more.

> std::cout <<
>         "    This is a demonstration of how to receive aligned data from multiple channels.\n"
>         "    This example can receive from multiple DSPs, multiple motherboards, or both.\n"
>         "    The MIMO cable or PPS can be used to synchronize the configuration. See --sync\n"
>         "\n"
>         "    Specify --subdev to select multiple channels per motherboard.\n"
>         "      Ex: --subdev=\"0:A 0:B\" to get 2 channels on a Basic RX.\n"
>         "\n"
>         "    Specify --args to select multiple motherboards in a configuration.\n"
>         "      Ex: --args=\"addr0=, addr1=\"\n"
>         << std::endl;

See this readme, there is a place where it should be convenient to
replace the DDC with custom logic:



> Thanks,
> Roy
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