Yes, that shows bursts of digital data, which is what your tx produces. Use a smaller FFT size to see more detail in the time domain.
On Sun, Jan 24, 2021 at 4:44 PM Jada Mariano Berenguer <beren...@uci.edu> wrote: > So, from my understanding you added a File Sink that took in the USRP > Source's output to the packet_usrp_tx.grc flowgraph? I tried to recreate > what you did and opened the file with Inspectrum and a screenshot of the > results is attached. I'm not sure if this is what you got, or what it > means. I may be saving it to the File Sink incorrectly, so I attached a > screenshot of the File Sink parameters as well. > > Also, what do you mean by 'What happens if you ignore this and keep > working' ? Because if I run the packet_usrp.grc flowgraph for a while and > ignore the U's printing out, it doesn't give me the result that I expect. > The result that I expect would be similar to the result when running the > packet_loopback_hier.grc file. > > Thanks again for your continued help! > > On Sun, Jan 24, 2021 at 12:03 PM Jeff Long <willco...@gmail.com> wrote: > >> Best I can tell (recording raw samples from the USRP Source to a File >> Sink, then viewing it with inspectrum), it works and the single 'U' per >> burst is spurious. The docs would lead you to believe you shouldn't see >> this. Nothing stands out as wrong in the GRCs. What happens if you ignore >> this and keep working? >> >> On Sun, Jan 24, 2021 at 1:41 PM Jada Mariano Berenguer <beren...@uci.edu> >> wrote: >> >>> Okay, thanks for the tip. Attached in this email is a flowgraph that >>> only does TX (packet_usrp_tx.grc). I'll continue to look into the problem >>> and see if I can find any solutions myself as well, but again I'm pretty >>> new to GNURadio and USRP. If anyone can help me figure out the problem, >>> it'd be greatly appreciated!! I've also attached the packet loopback >>> example using the USRP with both TX and RX (packet_usrp.grc), the original >>> packet loopback example without USRP (packet_loopback_hier.grc), and the >>> packet_tx and packet_rx flowgraphs as well. >>> >>> On Sat, Jan 23, 2021 at 4:36 AM Jeff Long <willco...@gmail.com> wrote: >>> >>>> Recommend you find the simplest flowgraph that demonstrates this >>>> problem. For example, do TX only. Once you find that minimal case, post the >>>> actual GRC file somewhere so someone can try it out. It's really difficult >>>> to look through a bunch of parameters in a screenshot and try to guess >>>> what's happening, unless it's something really obvious. >>>> >>>> On Fri, Jan 22, 2021 at 9:24 PM Jada Mariano Berenguer < >>>> beren...@uci.edu> wrote: >>>> >>>>> Hi again, I have a previous message thread regarding this problem, but >>>>> I kept forgetting to 'reply all' to include the GNURadio email to keep it >>>>> on the thread and my questions got kind of disorganized, so I wanted to >>>>> start fresh with a new one and will make sure to reply all in the future. >>>>> >>>>> So, I found a packet_loopback example (under the directory: >>>>> examples/digital/packet) from this message thread >>>>> <https://lists.gnu.org/archive/html/discuss-gnuradio/2018-06/msg00254.html> >>>>> and >>>>> it says that I can replace the Channel Model block with the USRP source >>>>> and >>>>> sink blocks to try to send packets over the air (a screenshot of the >>>>> original packet_loopback example and my modified packet_loopback example >>>>> is >>>>> attached as well). This is exactly what I want to do, but I'm running into >>>>> some issues with the USRP sink. >>>>> >>>>> I believe the problem has to do with the way that the USRP sink is >>>>> receiving the packets. I believe it deals with 'bursty transmission >>>>> <https://wiki.gnuradio.org/index.php/USRP_Sink>', and so I specified >>>>> the USRP sink's 'TSB tag name' parameter to 'packet_len', which is what >>>>> the >>>>> packet_tx block specifies as the length tag name (I've also attached a >>>>> screenshot of the packet_tx flowgraph). I confirmed that the tag name is >>>>> 'packet_len' by using the Tag Debug block. >>>>> >>>>> Also, I've attached a video link here >>>>> <https://drive.google.com/file/d/1n8SdwjbZebE4Mf4nufTUUnEALPNR0yDF/view?usp=sharing> >>>>> of what happens when I run the program. It seems like the USRP receives >>>>> the >>>>> packet here and there because of the short 'bursts' shown on the middle >>>>> graph. Also, I noticed that there's a 'tG' printed in the terminal window >>>>> (a screenshot of this is attached as well) when the program is first run. >>>>> What does this mean? I also know that it's experiencing a lot of >>>>> underruns, >>>>> which is essentially the problem I'm trying to solve. It must do with the >>>>> way the USRP sink is configured to receive the packets. >>>>> >>>>> Are there any other parameters that need to be set? >>>>> >>>>> Thanks so much in advance!! I appreciate any help :) >>>>> >>>>> >>>>>