http://ntpi.openchaos.org/pps_pi/
Only thing that I had to do in addition to the instructions was apt-get install bc, which was not present in the Raspbian image.
The GPS module in use is:
http://ava.upuaut.net/store/index.php?r ... duct_id=95
I have got Everything up'n'running, but theres a problem:
npt.conf looks like this:
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# /etc/ntp.conf, configuration for ntpd; see ntp.conf(5) for help
driftfile /var/lib/ntp/ntp.drift
server 127.127.22.0 minpoll 4 maxpoll 4
fudge 127.127.22.0 flag3 1 refid PPS
server 127.127.28.0 minpoll 4 maxpoll 4 prefer
fudge 127.127.28.0 time1 +0.140 refid GPS
restrict -4 default kod notrap nomodify nopeer noquery
restrict -6 default kod notrap nomodify nopeer noquery
# Local users may interrogate the ntp server more closely.
restrict 127.0.0.1
restrict 192.168.0.0 mask 255.255.0.0
restrict ::1
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root@raspberrypi:~# ppstest /dev/pps0
trying PPS source "/dev/pps0"
found PPS source "/dev/pps0"
ok, found 1 source(s), now start fetching data...
source 0 - assert 1403129104.019643681, sequence: 2303 - clear 0.000000000, sequence: 0
source 0 - assert 1403129105.019684923, sequence: 2304 - clear 0.000000000, sequence: 0
source 0 - assert 1403129106.019728164, sequence: 2305 - clear 0.000000000, sequence: 0
source 0 - assert 1403129107.019770406, sequence: 2306 - clear 0.000000000, sequence: 0
source 0 - assert 1403129108.019813649, sequence: 2307 - clear 0.000000000, sequence: 0
source 0 - assert 1403129109.019856891, sequence: 2308 - clear 0.000000000, sequence: 0
source 0 - assert 1403129110.019898134, sequence: 2309 - clear 0.000000000, sequence: 0
source 0 - assert 1403129111.019941377, sequence: 2310 - clear 0.000000000, sequence: 0
source 0 - assert 1403129112.019984620, sequence: 2311 - clear 0.000000000, sequence: 0
source 0 - assert 1403129113.020028864, sequence: 2312 - clear 0.000000000, sequence: 0
source 0 - assert 1403129114.020069108, sequence: 2313 - clear 0.000000000, sequence: 0
source 0 - assert 1403129115.020113352, sequence: 2314 - clear 0.000000000, sequence: 0
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x Time: 2014-06-18T22:05:55.000Z xxPRN: Elev: Azim: SNR: Used: x
x Latitude: 57.709936 N xx 1 52 277 49 Y x
x Longitude: 11.993469 E xx 3 25 179 36 Y x
x Altitude: 67.7 m xx 11 71 247 43 Y x
x Speed: 0.1 kph xx 14 42 089 22 Y x
x Heading: 0.0 deg (true) xx 17 05 320 27 Y x
x Climb: 0.0 m/min xx 19 43 174 33 Y x
x Status: 3D FIX (3 secs) xx 20 15 233 35 Y x
x Longitude Err: +/- 2 m xx 22 32 067 32 Y x
x Latitude Err: +/- 1 m xx 24 11 020 31 Y x
x Altitude Err: +/- 6 m xx 27 13 162 26 Y x
x Course Err: n/a xx 28 27 295 38 Y x
x Speed Err: +/- 14 kph xx 32 52 210 38 Y x
x Time offset: 0.678 xx x
x Grid Square: JO57xr xx x
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localhost:2947: Generic NMEA>
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xTime: 2014-06-18T22:07:34.000Z Lat: 57 42' 35.999" N Lon: 11 59' 36.730" E x
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x GPGSV GPGLL GPRMC GPVTG GPGGA GPGSA x
mqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq Sentences qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqj
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xCh PRN Az El S/N xxTime: 220734.00 xxTime: 220734.00 x
x 0 1 277 53 42 xxLatitude: 5742.59999 N xxLatitude: 5742.59999 x
x 1 3 179 25 26 xxLongitude: 01159.61217 E xxLongitude: 01159.61217 x
x 2 11 245 72 43 xxSpeed: 0.018 xxAltitude: 39.5 x
x 3 14 88 42 0 xxCourse: xxQuality: 2 Sats: 11 x
x 4 17 320 6 37 xxStatus: A FAA: D xxHDOP: 1.01 x
x 5 19 174 42 28 xxMagVar: xxGeoid: 38.2 x
x 6 20 233 16 42 xmqqqqqqqqqqq RMC qqqqqqqqqqqqjmqqqqqqqqqqq GGA qqqqqqqqqqqqj
x 7 22 67 31 29 xlqqqqqqqqqqqqqqqqqqqqqqqqqqqqklqqqqqqqqqqqqqqqqqqqqqqqqqqqqk
x 8 24 20 11 27 xxMode: A 3 xxUTC: RMS: x
x 9 27 162 13 31 xxSats: 20 32 3 19 2...4 17 2 xxMAJ: MIN: x
x10 28 294 27 33 xxDOP: H=1.01 V=1.21 P=1.57 xxORI: LAT: x
x11 32 210 53 41 xmqqqqqqqqqqq GSA qqqqqqqqqqqqjxLON: ALT: x
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root@raspberrypi:~# ntpq -np
remote refid st t when poll reach delay offset jitter
==============================================================================
x127.127.22.0 .PPS. 0 l 1 16 377 0.000 -0.659 0.279
x127.127.28.0 .GPS. 0 l 15 16 377 0.000 -1.979 1.465
root@raspberrypi:~#What are causing ntp to exclude them?
I SUSPECT its the rPI system Clock that is the culprit, that the builtin Clock in rPI isnt accurate since its not a RTC, and NTP then uses the system Clock to decide if the PPS source and GPS source is good.
But then - how can I configure ntpd to "distrust" the system Clock and assume that the system Clock is "rogue", eg Always assume the system Clock stupidly wrong.