Hello, In case anyone else has a similar problem: I could finally solve the issue in gnuradio including a python snippet before init using the set_start_time() command for both source and sink blocks. Now all 4 TX and RX channels are running without any problem.
Balint Bálint Horváth <horvl...@gmail.com> ezt írta (időpont: 2020. szept. 7., H, 18:30): > Hello Rob, > > Thank you very much for your advice. The benchmark test is working on all > 4 channels for 1 MSamp/sec, which is sufficient for the current application > (though sometimes there are some S and U at startup). The ram drive did not > solve the problem, however if I set a settling time for 1 (sec) for the > txrx_loopback it started working for the 4 channels. In this case the RX > starts only 1 sec after the TX. So it kind of seems like there is a problem > at startup and after that everything is fine. I don't know if that makes > sense though. > > I tried to make the settling time thing happen in gnuradio with > issue_stream_cmd after init/start with a python snippet, but oddly there is > a very short time at startup when both TX and RX are active, and the > command seems to take effect only after that. Maybe I'm missing something > here. > > So now I'm trying to merge and customize the txrx_loopback with the > tx_samples from file examples hoping that it will work. > > Also I checked the CPU load with htop and it is only 15% on all 4 cores > during the loopback. > > Any further advice is still welcome! > > Balint > > Rob Kossler <rkoss...@nd.edu> ezt írta (időpont: 2020. szept. 3., Cs, > 19:55): > >> Hi Bálint, >> You may want to step backwards once more and run the "benchmark_rate" >> utility with 4 channels with tx & rx rates at 1MHz. This will eliminate >> the file I/O considerations (both for tx and rx). If benchmark_rate is >> successful, see how high you can increase the rate. The n4200 is not a very >> powerful CPU, so you might be significantly limited. If you are using the >> 1Gb interface, then the max sample rate you can achieve (assuming your CPU >> is not limiting you) for 4 channels is ~6.25 MS/s because of the 1Gb limit >> (4 chan x 6.25MS/s x 4 bytes/sample x 8 bits/byte = 800Mb/s). >> >> Once you are satisfied with the USRP streaming rates, you can try putting >> your tx and rx files in a ram drive in order to improve the file I/O so >> that it does not impact overall performance appreciably. Then retry >> txrx_loopback_to_file. >> Rob >> >> >> On Thu, Sep 3, 2020 at 3:23 AM Bálint Horváth via USRP-users < >> usrp-users@lists.ettus.com> wrote: >> >>> Hello, >>> >>> I have a USRP N310 and in my application I want to do a 4 channel >>> loopback. Transmit sources are files and the received samples are >>> processed. However, I ran into stability issues receiving a lot of Late >>> packet errors (LLLLL). To trace the problem I executed the basic UHD >>> example txrx_loopback_to_file on 4 channels with 1Msamp/sec sample rate. >>> There every time I got ERROR_CODE_LATE_COMMAND. When I executed it for 3 >>> channels I got it working, though on some occasions the same error would >>> occur. With netstat I see that in case I receive the L-s, the UDP packet >>> error is increasing. >>> >>> After reading through the manual and threads I tried several things but >>> could not resolve the issue. >>> - I set the net.core.rmem_max and wmem_max as suggested >>> - I set the MTU on both host and N310 to 8000 (also tried 1500) >>> - I put the CPU to performance mode with cpupower >>> >>> My system config is: >>> - Ubuntu 20.04, UHD version 3.15, (gnuradio installed with apt) >>> - quad core intel n4200, 8GB RAM >>> - N310 is loaded with default HG firmware (sfp0 is 1GBit) >>> >>> Do you have any tips on how to resolve this? >>> >>> Thanks! >>> >>> Balint >>> _______________________________________________ >>> USRP-users mailing list >>> USRP-users@lists.ettus.com >>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >>> >>
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