Steven Underflow is a TX error phenomena, not an RX one. It is signaled when the local buffering of TX data in the USRP becomes empty whilst the USRP tries to continue to transmit. Late, on the other hand, is signaled when a TX command contains a time that is later than the USRP’s local clock when it is executed.
Hope this is helpful, -Ian > On Feb 8, 2018, at 1:33 PM, Steven Knudsen via USRP-users > <usrp-users@lists.ettus.com> wrote: > > Hi, > > I have been scratching my head for a while on this one… > > I have made a TDMA radio that has a simple 4 slot cycle with a relatively low > duty cycle (slots are 40% and the remaining 60% of the cycle the USRP is > idle). > > A radio transmits in it’s “owned” slot and receives in all others (3 of > them). The transmit is timed as are the receptions in each slot. Transmit is > schedule 10 ms in advance (at the start of a cycle) and the receives are > scheduled at least 6 ms in advance (at the end of the last receive slot). > > When I test with a B200mini connected to an Octoclock G for 1 PPS reference, > it runs flawlessly for hours (5 is the longest). When, on the exact same > Linux host I run with an X310 connected to the same Octoclock G for 1 PPS and > 10 MHz, it stops working after not too long with a slew of ’U’s and ’L’s > > Trying to narrow things down, I created a version fo the radio that only > transmits. Reception is completely disabled and I confirm that no receive > commands are ever scheduled and rxStreamer->recv() is never called. > > So, imagine my surprise when after a fairly long time of transmitting > successfully (evidenced by using an oscilloscope to view packets), the > transmit-only version fails!?! Below is a copy o the log showing the first > evidence of failure, namely ’L’s indicating transmits were too late. But, > what is the ‘U’ doing there? As I mentioned, no reception functionality is in > the program, so what is going on? > > Anyone else see this kind of thing? I never see it with the B200mini, but see > it consistently with the X310. > > thanks very much for your time and consideration, > > steven > > ULLsendFrame() MPDU #719935 mpdu size = 488 bytes at 1518123481s 890000 us > ULLLsendFrame() MPDU #719936 mpdu size = 488 bytes at 1518123481s 900000 us > ULLLLsendFrame() MPDU #719937 mpdu size = 488 bytes at 1518123481s 910000 us > ULLLLLsendFrame() MPDU #719938 mpdu size = 488 bytes at 1518123481s 920000 us > ULLLLLLsendFrame() MPDU #719939 mpdu size = 488 bytes at 1518123481s 930000 > us > ULLLLLLLsendFrame() MPDU #719940 mpdu size = 488 bytes at 1518123481s 940000 > us > ULLLLLLLLsendFrame() MPDU #719941 mpdu size = 488 bytes at 1518123481s > 950000 us > ULLLLLLLLLsendFrame() MPDU #719942 mpdu size = 488 bytes at 1518123481s > 960000 us > ULLLLLLLLLLsendFrame() MPDU #719943 mpdu size = 488 bytes at 1518123481s > 970000 us > ULLLLLLLLLLLsendFrame() MPDU #719944 mpdu size = 488 bytes at 1518123481s > 980000 us > ULLLLLLLLLLLLsendFrame() MPDU #719945 mpdu size = 488 bytes at 1518123481s > 990000 us > ULLLLLLLLLLLLLsendFrame() MPDU #719946 mpdu size = 488 bytes at 1518123482s > 0 us > ULLLLLLLLLLLLLsendFrame() MPDU #719947 mpdu size = 488 bytes at 1518123482s > 10000 us > ULLLLLLLLLLLLLLsendFrame() MPDU #719948 mpdu size = 488 bytes at 1518123482s > 20000 us > ULLLLLLLLLLLLLLLsendFrame() MPDU #719949 mpdu size = 488 bytes at > 1518123482s 30000 us > ULLLLLLLLLLLLLLLLsendFrame() MPDU #719950 mpdu size = 488 bytes at > 1518123482s 40000 us > ULLLLLLLLLLLLLLLLLsendFrame() MPDU #719951 mpdu size = 488 bytes at > 1518123482s 50000 us > ULLLLLLLLLLLLLLLLLLsendFrame() MPDU #719952 mpdu size = 488 bytes at > 1518123482s 60000 us > ULLLLLLLLLLLLLLLLLLLsendFrame() MPDU #719953 mpdu size = 488 bytes at > 1518123482s 70000 us > > > > Steven Knudsen, Ph.D., P.Eng. > www. techconficio.ca <http://techconficio.ca/> > www.linkedin.com/in/knudstevenknudsen > <http://www.linkedin.com/in/knudstevenknudsen> > > All the wires are cut, my friends > Live beyond the severed ends. Louis MacNeice > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com <mailto:USRP-users@lists.ettus.com> > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > <http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com>
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