[USRP-users] Configuring RX connection type on N210/TVRX2

Julian Ilinca julian.ilinca.fgi at gmail.com
Fri Nov 15 05:02:15 EST 2019


Hello all,

I have two questions concerning the RX channel configuration on an TVRX2
daughter-board. I cannot seem to find any relevant information in the
example files or on the Internet. But first things first, the TVRX2 is
connected to a N210 motherboard and I am using the UHD C++ API for
configuring the device. Furthermore, I am trying to measure the real (I)
component of a VHF signal on both of the channels (RX1 and RX2)
simultaneously.

1. The first question is related to IQ sampling:
The daughter-board is set so that one channel retrieves the I component and
the other channel the Q. I retrieved this information with the
uhd_usrp_probe command. In the output under RX0 its says connection type =
Q and on RX1 connection type = I. What command do I have to use to change
connection type of RX0 from Q to I, so that I could have two channels
measuring the real component.

2. I'm a confused about the channel mapping convention used when using the
TVRX2. In order torecord from two channels I have set the subdev_spec to
"A:RX1 A:RX2", and it works fine. However, when I use the
"get_rx_num_channels()" function its return value is 1 instead of 2.
In the manual entry for the function it says:

"This is the number of USRPs times the number of RX channels per board,
where the number of RX channels per board is homogeneous among all USRPs."

To get streaming arguments correctly I have to use a vector where I map the
channel number s1 and 2 manually:

>>std::vector<size_t> channel_nums;
>>...
>> channel_nums.push_back(0);
>> channel_nums.push_back(1);
>>...
>>stream_args.channels = channel_nums;
>>uhd::rx_streamer::sptr rx_stream = usrp->get_rx_stream(stream_args);

Now, how does the device recognize 2 channels after the get_rx_stream()
function has been called, as it earlier on told me there is only one
channel, and how can I specifically configure the properties of channel 1?

Thanks already in advance for your support!

Br. Julian
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