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Re: Transmitting on both channels on USRP X300


From: Marcus D. Leech
Subject: Re: Transmitting on both channels on USRP X300
Date: Wed, 22 Jan 2020 22:07:43 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0

On 01/22/2020 07:26 PM, Sunny Sam wrote:
Hi everyone,

I am trying to transmit data from two UDP sockets using the two USRP X300 TX lines. I modified the tunnel.py example to do this. The modulated signals from the two UDP sockets are connected to the UHD USRP Sink block input 0 and 1. What I have noticed is, the work function for the USRP Sink block does not get called until there is data on both UHD USRP sink input lines. And, it only transmit when it receives the same number of data on both input lines at the same time. Is there a way to make the USRP Sink block transmit the received data on any input line without waiting for data on the other input line? I also noticed if I just start the top block, tb.start(), I get a lot of late packets (LLLLL). If I start, stop, and start the top block again as shown below, I don't get the late packets print. I feel like this is related to the USRP Sink block not initializing both input lines with the first tb.start() call. Is my assumption correct? Is there a better way to do this? Please advise.

tb.start()
time.sleep(0.25)
tb.stop()
time.sleep(0.25)
tb.start()


Thank you in advance.

Gnu Radio is fundamentally a *streaming* architecture. So, it naturally needs all streams to be running at the same time.

There are mechanisms, using tagged-streams to do "burst" transmissions, but I'm not really an expert on how to make those work.

I'll observe that tunnel.py is, as far as I know, woefully out-of-date with respect to underlying Gnu Radio mechanisms, etc.

You might be better off starting with a clean sheet of paper, so to speak.





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