Re: Confusion about 'ports'

[Chad Spooner]

Marcus:

Yes, I did miss that reply! Very sorry about that. Let me try to answer your questions:

First, I did try to use a single Source block with two channels on the advice of a colleague. I've been unable to get that to work either. (More on that below, after I answer your questions.)

The x310 has WBX (A) and UBX (B) daughtercards.

The x310's UBX RX2 input is coming from the TX/RX output of an N210 with a WBX daughtercard. The N210 is generating a DSSS signal and transmitting it on TX/RX.

The x310's WBX RX2 input is coming from a passive antenna (Ettus WA5JVB Log Periodic 850 MHz to 6500 MHz).

The x310's UBX TX/RX transmits the sum of the UBX RX2 and WBX RX2 signals.

A third SDR (x300) receives the x310's UBX TX/RX signal and that is the USRP I fetch data from using uhd_rx_cfile.

********

When I try the single Source block with two channels:

Here I switched around the cables.

B RX2 receives the signal from the N210 as before.

B TX/RX receives the signal from the antenna.

A TX/RX outputs the sum of the B RX2 and B TX/RX signals.

The error is:

PCS_band_AOC.py", line 97, in __init__
    self.uhd_usrp_source_0_1.set_samp_rate(samp_rate)
RuntimeError: LookupError: IndexError: [legacy_compat]: RX channel 1 out of range for give
n frontend configuration.

Is this telling me I need a different FPGA image? Is that what you mean by "multichannel configuration?"

I did search around for clues about this error (and the other one), knowing your time is valuable, but I've come up empty. (Your guess about me either not seeing or not understanding your reply is on the mark. I do put in effort to understand the UHD and gnuradio documentation, but I definitely fail.)

I'm also confused why it matters what the signals are on the two inputs--I could terminate those inputs instead of connecting them to the antenna and the N210. The flowgraph still won't run.

Thanks! I'll do better on looking for your responses, I promise.

C

On 3/16/22 1:31 PM, Marcus D. Leech wrote:

On 2022-03-16 15:41, Chad Spooner wrote:

Some information I should have included the first time:

OS: Ubuntu 20.04.3

gnuradio: 3.9.4.0

UHD: 3.15.0.0-2build5

Maybe somebody has a simple shareable flowgraph running under these conditions and that has two USRP Source blocks and one USRP Sink block?

Thanks,

C

On 3/14/22 4:02 PM, Chad Spooner wrote:

All:

I've got a simple flowgraph with two USRP Source blocks and a single USRP Sink block:

This flowgraph is running on an x310. The upper Source block is supposed to stream data coming from another SDR, and the lower Source block is supposed to stream data from an antenna. Then I add these together and output the sum with the Sink block.

When I run it I get this error:

gr::log :ERROR: thread_body_wrapper - ERROR thread[thread-per-block[2]: <block usrp_source
(1)>]: RuntimeError: On node 0/DDC_0, output port 0 is already connected.

If I disable one of the Source blocks, things work as expected, so it is the presence of both that is the problem.

I can't tell from the documentation what a 'port' is, exactly. And there isn't any error message in the companion itself, so I guess it thinks this is OK.

Can somebody please point me to a clear discussion of how 'ports' enter here or please suggest a way to modify the flowgraph?

Thanks,

C

Chad:

I put what I thought was a reasonable effort into my previous reply on this subject, which you either didn't see, or didn't understand.

You *CANNOT* "splilt" a USRP hardware device across multiple source/sink blocks.  If your device has multiple channels that you wish to
  take advantage of, you must have that device in a single block, and use a multi-channel configuration to produce multiple outputs.

You haven't yet responded to my request for a notion of the hardware configuration of your USRP devices--one I think is an X310--but you hadn't
  mentioned what the RF daughtercard configuration is, so none of us here can give really-detailed advice.

-- 
Chad M. Spooner, PhD
NorthWest Research Associates
301 Webster Street
Monterey, CA 93940
cmspooner@nwra.com
831 582 4904
cyclostationary.blog

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