Simchaev Arthur-BAS071 wrote:
Hi .
Could you please help me with the following problem ?
Our board supports PPS & NTP . I connect & define the Garmin GPS(GPS16x-HVS) as
the NMEA reference clock . Unfortunately when I add the atom reference clock to ntp in
order to receive pps , after sometime NMEA & ATOM(pps) clocks marked as falsetick
servers . I see that it can related to the jitter and can be fixed by setserial low_latency
. But out UART doesn't support this flag .
Therefore could you please explain how I can fix servers falsetick problem
witout use setserial . Maybe the problem related to number of the servers (I
use only only 2 stratum 0 servers which take the data from the same GPS device
)
Our configuration is following :
Ntp configuration (ntpd 4.2.6p5) :
server 127.127.1.0 #lo server
fudge 127.127.1.0 stratum 7
restrict 127.127.1.0 noquery nomodify notrap
server 127.127.20.0 minpoll 4 maxpoll 4 iburst #NMEA Server
server 127.127.22.0 prefer
fudge 127.127.22.0 flag3 1 refid PPS
I currently use a "Sure" gps, ntp-dev-4.2.7p433 on NetBSD-6
I have a few significant differences in my ntp.conf
#################
tos orphan 10
tos mindist 0.4 # allows pps to kick in
^^^^^^^^^^^
server 127.127.20.2 mode 18
fudge 127.127.20.2 stratum 7 time2 0.407 flag1 0 refid GPSb
server 127.127.22.2 minpoll 4 maxpoll 4
server 127.127.22.2 flag2 0 flag3 1 refid PPSb
server -4 <ntp0.mydomain>
server -4 <ntp1.myisp> minpoll 8 maxpoll 10 iburst prefer
##################
If not using extra server use 127.127.20.0 as prefer peer.
David
ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
*LOCAL(0) .LOCL. 7 l 5 64 377 0.000 0.000 0.031
xGPS_NMEA(0) .GPS. 0 l 4 16 377 0.000 -63.203 5.256
xPPS(0) .PPS. 0 l 3 64 377 0.000 -347.47 7.428
root@am335x-evm:/dev# ntpdc
ntpdc> kerninfo
pll offset: 0 s
pll frequency: 0.000 ppm
maximum error: 0.013456 s
estimated error: 1e-05 s
status: 2007 pll ppsfreq ppstime nano
pll time constant: 6
precision: 1e-09 s
frequency tolerance: 500 ppm
root@am335x-evm:/dev# ntptime
ntp_gettime() returns code 0 (OK)
time d6dd71e6.aaf4cf0c Wed, Mar 26 2014 15:33:58.667, (.667798707),
maximum error 23956 us, estimated error 10 us, TAI offset 0
ntp_adjtime() returns code 0 (OK)
modes 0x0 (),
offset 0.000 us, frequency 0.000 ppm, interval 1 s,
maximum error 23956 us, estimated error 10 us,
status 0x2007 (PLL,PPSFREQ,PPSTIME,NANO),
time constant 6, precision 0.001 us, tolerance 500 ppm,
Regards
Arthur
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