Hi, I played around with the subdev specs. They are all alike. I found the bug. For some reason GRC generated flowgraphs lack a call to `self.uhd_usrp_source_0.set_gain(gain, 0)` whenever the gain variable is changed. This was not a huge problem for X310s because they perform quite nicely with RXgain=10 in my setup. But for the N310s, I needed to set RXgain=40 before I generate the flowgraph because the gain callback is missing. I will update GR and open a new issue if the bug persists.
Thanks for all your help! Johannes On 22.10.19 17:38, Robin Coxe wrote: > The subdev spec mappings for the N310 are in the getting started guide > on the Ettus KB. > > > UHD 3.13.x.x+ > > * RF0 = A:0 > * RF1 = A:1 > * RF2 = B:0 > * RF3 = B:1 > > > Have you tried simple sanity checks such as inputting a single tone into > each N310 RX chain and progressively increasing the gain and plotting > with ascii FFT? (We did this analysis extensively during V&V testing, > as indicated on the N310 datasheet, so unless your system is configured > incorrectly or has a HW problem, you shouldn't see what you're seeing.) > If you think there's a HW problem with your unit, I'd suggest contacting > NI for an RMA. > > -Robin > > > On Tue, Oct 22, 2019 at 3:16 AM Johannes Demel <de...@ant.uni-bremen.de > <mailto:de...@ant.uni-bremen.de>> wrote: > > Hi Robin and Marcus, > > Thanks for your hints. > > UHD 3.14.1.1 work perfectly fine with my X310s. Only the N310s seem to > have problems. I use the default HG FPGA image that ships with 3.14.1.1. > > For the moment, I use `VERT2450` antennas. The ones you can order from > Ettus. I transmit/receive @2.484GHz. I mounted antennas on all antenna > ports. So for the N310s that's a total of 8 antennas per device. > So far I did not specify a `Subdev Spec` in GRC. > > I tried a few more options. Also, I unmounted the antennas on the RX2 > ports on the N310s and made sure the `TX/RX` antenna port is configured. > > Here are my observations: > 1. X310 -> X310 everything works fine TXgain=20, RXgain=10. > 2. N310 -> X310 everything works, though I need to raise TXgain=38 a > bit. > 3. X310 -> N310 works but it seems like sensitivity is still bad. I > need > to raise TXgain=70. RXgain seems to not make a difference at all. > 4. N310 -> N310 bad performance but transmission is possible. Need to > raise gains to almost maximum for bad performance. > > This is the N310 setup code generated by GRC. I tried different `Subdev > Spec`s for both TX and RX. I obtained the best results with `B:0` > for TX > and RX. Though, `best` is still way worse than X310 performance. > uhd.usrp_source( > ",".join(("addr=X.X.X.214", "")), > uhd.stream_args( > cpu_format="fc32", > args='', > channels=[], > ), > ) > self.uhd_usrp_source_0.set_subdev_spec('B:0', 0) > self.uhd_usrp_source_0.set_center_freq(tfreq, 0) > self.uhd_usrp_source_0.set_gain(rgain, 0) > self.uhd_usrp_source_0.set_antenna('TX/RX', 0) > self.uhd_usrp_source_0.set_samp_rate(samp_rate) > > Since Option 2 N310 -> X310 does yield good results, I assume that the > N310 RX chain or configuration is the problem. Though, I have no idea > how to debug that and which knobs to turn. > I tried to observe the spectrum with an N310 via `uhd_fft` from > `gr-uhd/examples/grc` and it feels like the N310 just doesn't case > about > RXgain settings. > > Johannes > > > On 18.10.19 20:42, Marcus D Leech wrote: > > What antenna are you specifying and which port are you rurally > plugged in to. > > > > Are you using offset tuning? That may be necessary for Narrow > signals near the tuned frequency, due to DC offset removal. > > > > On 18.10.19 16:24, Robin Coxe wrote: > > Hi Johannes. That low response from the N310 sounds fishy. Have > you > > tried another channel besides 0 on your N310? It might be that: > 1) the > > TX and RX cables are connected backwards (note that the order on the > > panel is funky due to layout constraints with the AD9371 RF IC on > the > > daughter cars. 2) signals are actually on the adjacent channel— > > double-check the UHD subdev mappings listed in the Getting > Started Guide > > because if memory serves they changed at some point— or 3) or the > SMA > > connector center pin connections might be cracked. > > > > Also, I’m not sure how compatible GR3.8 is with UHD 3.14.1. > Someone > > who still works on Ettus products mentioned at GRCon that you > have to > > use master-next branches, but those use the new RFNoC, which is > still > > largely uncharted territory with the N310 as far as I can tell. > > > > -Robin > > > > > > > ------------------------------------------------------------------------ > > *From:* USRP-users <usrp-users-boun...@lists.ettus.com > <mailto:usrp-users-boun...@lists.ettus.com>> on behalf of > > Johannes Demel via USRP-users <usrp-users@lists.ettus.com > <mailto:usrp-users@lists.ettus.com>> > > *Sent:* Friday, October 18, 2019 4:06 AM > > *To:* usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com> > > *Subject:* [USRP-users] N310 sensitivity > > Hi all, > > > > I figured out how to use our new N310s. > > > > I ran into the next issue. Let me describe this one briefly. > > > > With our X310s I set TXgain=20 and RX_gain=10. Both devices are 1-2m > > apart. I observe a really nice RX constellation with gr-gfdm and > > XFDMSync with bursts every 1ms (burst length ~50us). With our N310s I > > set RXgain=60, TXgain=70 and still, the constellation is very noisy. > > My assumption is that some part of the RX chain is not configured > > correctly. But I don't know what the problem is in particular. > > Also, I used an X310 as transmitter and an N310 as receiver. But the > > result is the same, the RX constellation is really noisy. > > > > Another observation is, that my RX sample stream in a GR time > sink does > > show quantization artifacts. i.e. I can see discrete steps which I > > assume are due to low RX sensitivity. The RX value amplitude is > around > > 0.0005 for the samples that I get of a USRP source. I assume this > should > > be a higher value. With the X310s it was more like 0.1. > > > > Do I need to take special care when I only use 1 antenna port? > > Is there another AGC setting that I need to configure for N310s? > > > > Johannes > > > > Software > > UHD: 3.14.1.1 > > GR: 3.8 > > _______________________________________________ > > 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 > _______________________________________________ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
