Sam- So I am actually using a gps satellite simulator(Labsat). This plays back previously recorded data and there are a number of test scenarios on there for me to use. Currently I am using a simple static one recorded in the UK I think. To protect the output I insert a DC block in. For the GPS rxrs in the E310, and X310 this has worked great and they lock up pretty quickly although the X310 does take longer than the E310. That E310 Ublox receiver is really fast.
I will send my serial numbers to Ettus support but given what you said about the E320 I decided to go back to basics and see if I could get the N310 I have to reliably lock and I learned some interesting things about it and its GPS. After extensive debugging all day using gpsmon I have learned that the N310 GPS (Jackson Labs LTE Lite) is very finicky it would seem. I found the following kind of works: 1)Power up the N310 from a cold start (unplugged at first because it seems the board gets power even before you hit the switch). 2)Run a uhd_usrp_probe –args “time_source=gpsdo,clock_source=gpsdo” to force it to switch the daughtercards over 3)set the system date and time to be close to the signal coming from the labsat. (Maybe this does not matter but then TOFF is not so out of wack. 3)Then run gpsmon and watch it acquire. Almost immediately SNR is good (45-50) and TPV shows lat and long, quality is 2 and it has 8 sats. Then we wait. 4)Eventually it will acquire(takes 7-8 mins) meaning that the GPS light will turn on and when I run the sensor query it reports back locked. While this seems to take forever it is repeatable. Now the fun starts. If after I have got it to lock up and then one of two things happens, either the labsat file rolls over or I disconnect the signal from the jack, gpsmon will show low SNR and eventually it will unlock. This makes sense I although the rollover thing is weird because ublox does not have an issue with that. What is really annoying is that when I plug the signal back in or restart the labsat the GPS never seems to try to re-acquire and there seems to be no way to restart it. A reboot does not fix it. Only a complete power down and disconnect from power seems to restart the GPS. It gets in some messed up state and that’s it. Does that seem normal? My N310s are fairly old. Did they have some GPS recall at some point? By the way I noticed in its screwed up state it no longer sends GSV strings and if you decide to do a N310 bist gpsdo it will totally wipe out the GPS module and it seems to no longer output pps or the ref too. Probably not intended behavior? I have some screenshots of gpsmon if you are interested. I did not want to blast the list with images. Let me know and I can send them. I am going to do some experimenting with the E320 and see if it behaves similarly. I bought my E320s very recently so I would be surprised if they needed that fix (Serial #31C8CC6). I did notice in the VHDL top for the E320 that there are some pin controls to the GPS module which I did not see in the N310 top. This could mean that there is more control over the E320 GPS?? I was thinking of chipscoping those pins maybe too and see how they change with UHD startup etc.. Thanks Jeff From: Sam Reiter <sam.rei...@ettus.com> Sent: Tuesday, March 24, 2020 9:48 AM To: Long, Jeffrey P. <jpl...@mitre.org> Cc: usrp-users@lists.ettus.com Subject: [EXT] Re: [USRP-users] E320 GPS staying locked? Hey Jeff, What type of GPS antenna are you using? 3.3V or 5V? If it's compatible with X310 & other USRPs, I would imagine you'll be good to go with the E320... Do you see the locked / unlocked status change between consecutive runs of something like gpsmon on the E320? There were some early-ish runs of the E320 that are eligible for a GPSDO rework, feel free to send supp...@ettus.com<mailto:supp...@ettus.com> a direct email with your E320's serial number and I can see if yours is one of the affected units. Sam Reiter On Mon, Mar 23, 2020 at 4:27 PM Long, Jeffrey P. via USRP-users <usrp-users@lists.ettus.com<mailto:usrp-users@lists.ettus.com>> wrote: Has anyone had issues with the E320 GPS locking or staying locked? I have a LabSat GNSS simulator that I am reliably able to get a E310, X310, and even a N310 to lock to however the E320 I just got will occasionally lock and then fall out almost immediately. I used mender to up it to 3.15LTS and everything else works pretty well. I run the e320bist on the gpsdo and it reports it mostly being unlocked but occasionally it will lock for a minute or so. When it does lock I can run the query gpsdo immediately after and it will report locked but again it only lasts for a min or so. Thanks Jeff _______________________________________________ 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
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