I'm trying to get NTP working with GPS on the E310. In the past, I've gotten it
to work with the old release 4 images (UHD 3.9.2), but with latest meta-ettus
images (UHD 4.1.0), only the serial GPS data is getting NTP (via SHM), and not
the PPS data, so the accuracy isn't great.
The approach configured out of the box for release 4 has NTP connecting
directly to the PPS device (using the server 127.127.22.0 alias). This approach
doesn't work with the new images as there are no /dev/ppsX devices - in fact
PPS support isn't even compiled into the kernel:
root@ni-e31x-3203241:~# zcat /proc/config.gz | grep -i PPS
# CONFIG_PPS is not set
Compare to release 4 image output:
root@ettus-e3xx-sg3:~# zcat /proc/config.gz | grep -i PPS
# PPS support
CONFIG_PPS=y
# CONFIG_PPS_DEBUG is not set
# PPS clients support
# CONFIG_PPS_CLIENT_KTIMER is not set
# CONFIG_PPS_CLIENT_LDISC is not set
CONFIG_PPS_CLIENT_GPIO=m
# PPS generators support
Last month a message on this list[1] suggested that the following ntp.conf
(which uses GPSD SHM for both Serial and PPS data) should work:
# GPS Serial data reference
server 127.127.28.0 minpoll 4 maxpoll 4
fudge 127.127.28.0 time1 0.0 refid GPS
# GPS PPS reference
server 127.127.28.1 minpoll 4 maxpoll 4 prefer
fudge 127.127.28.1 refid PPS
Unfortunately, I haven't had success with that either. NTP is just getting
serial GPS updates, not PPS:
root@ni-e31x-3203241:~# ~/install/usr/local/bin/ntpq -p
remote refid st t when poll reach delay offset
jitter
==============================================================================
*SHM(0) .GPS. 0 l 7 16 377 0.000 -1.830
3.126
SHM(1) .PPS. 0 l - 16 0 0.000 +0.000
0.000
Starting gpsd with -D3 gives the following startup logs:
GPS: Activating GPS antenna supply voltage...
GPS: Activating GPS PPS...
gpsd:INFO: /etc/gpsd/device-hook returned 0
gpsd:INFO: SER: opening GPS data source type 2 at '/dev/ttyPS1'
gpsd:INFO: SER: speed 9600, 8N1
gpsd:INFO: SER: speed 9600, 8O1
gpsd:INFO: SER: speed 9600, 8N1
gpsd:INFO: SER: speed 9600, 8N1
gpsd:INFO: SER: speed 9600, 8N1
gpsd:INFO: gpsd_activate(2): activated GPS (fd 7)
gpsd:INFO: KPPS:/dev/ttyPS1 cannot set PPS line discipline unknown error
gpsd:WARN: KPPS:/dev/ttyPS1 kernel PPS unavailable, PPS accuracy will
suffer
gpsd:INFO: PPS:/dev/ttyPS1 ntpshm_link_activate: 1
gpsd:INFO: device /dev/ttyPS1 activated
Does the new image use a different API to get the PPS data to gpsd/ntpd that I
need to configure?
Thanks,
Jackson
[1] https://lists.ettus.com/empathy/thread/YRNSBGDFVCXJDLOVHFYWMDVC5F3QAK5J
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