Hey all Just wondering if anyone had a chance to look at this for me. I'd appreciate it immensely! Thank you.
On Fri, Mar 2, 2018 at 3:37 PM, Keith k <keithko...@gmail.com> wrote: > Hello all > > I'm working on a project to use 16 N200s in a multi USRP configuration for > a radar project. They are synchronized using 3 Octoclocks (one master with > a GPSDO, and two slaves that drive the 16 N200s). I've been getting many > errors that I was hoping someone could help with. I have attached a sample > program that mimics how the USRPs are used. The basic goal here is to > sample a determined number of samples while transmitting some spaced pulses > (a "pulse sequence") and then repeat. It would be beneficial to have as > little delay as possible in between loops. I've been running into some > problems however. > > BASIC INFO > We have 16 N200s + 1 spare > 3 Octoclocks (1 has gps and it drives the other two) > LFTX and LFRX daughterboards in each N200 > linux; GNU C++ version 4.8.5; Boost_105400; UHD_003.010.002.000-0- > gbd6e21dc > Intel Corporation Ethernet Controller 10-Gigabit X540-AT2 > Devices are all connected via 3 daisy chained Netgear XS708E switches > Ideal sampling rates: 5-10MHz TX, 5-10MHz RX depending on > hardware/software limitations. > > One of the issues I sometimes get after several minutes of runtime (or > several thousand pulse sequences) is the overflow(O) with the out of > sequence flag set in the rx metadata. I also get sequence errors(S) on the > tx side too. It seems to happen more often and faster with higher sampling > rate. I've gathered from other mailing list posts that this is likely a > network configuration issue. Can someone recommend a known working computer > build and network configuration that can handle the amount of USRPs and > data we are attempting to use? > > Another major issue I eventually get during runtime is a slurry of > lates(L) on TX and then a LATE in the RX metadata. I've tried increasing > the time in the future that the TX/RX should start (from when the stream > commands are called) and I've tried to minimize the number of operations > happening between that calculation and when TX/RX start, but the lates > still eventually happen. I've tried to time profile what I can in my code > and it seems I should really only need about ~0.5ms of delay, but even at > 3-10ms of delay I have issues. I feel like 10ms of time should be more that > plenty of time for the host to issue stream commands. I don't seem to get > lates if I have test applications that individually test TX or RX, but when > I put them together using threads, I can't seem to find a way to eliminate > the lates. Any ideas on how I should set up what I'm trying to do here? > > Here is the compiler line to make the test program: > g++ -o test_rx_tx -std=c++11 -Wall test_rx_tx.cpp -lboost_system -luhd > > If I can explain anything in further detail please let me know. > > Thank you for your time. > > -- > -Keith Kotyk > -- -Keith Kotyk
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