[ntp:questions] high jitter and offset with linux and sure GPS

Olivier Frappier olivier.frappier at live.fr
Fri Jan 4 17:06:50 UTC 2013


Hi,

I'm unable to have 1us precision with Sure GPS card and NTP :

_ ubuntu 12.04 LTS / Kernel 3.2
_ SURE GPS :
http://www.satsignal.eu/ntp/Sure-GPS.htm
(PPS modifications done)
- ntp atched with timepps.h (but i'm not sure it's work)

09.pps.rules :



	
	
	
	


KERNEL=="ttyS0",
SYMLINK+="gps0"
KERNEL=="ttyS0",
RUN+="/bin/setserial -v /dev/%k low_latency"
KERNEL=="ttyS0",
RUN+="/usr/sbin/ldattach pps /dev/%k"
KERNEL=="pps0",
OWNER="root", GROUP="tty", MODE="0660",
SYMLINK+="gpspps0"




	
	
	
	


etc/apparmor.d/tunables/ntpd :


	
	
	
	


@{NTPD_DEVICE}="/dev/ttyS0


	
	
	
	


server
127.127.20.0 iburst minpoll 4 prefer mode 18
fudge
127.127.20.0 flag1 1 flag2 0
#
time1: PPS time offset
#
time2: Serial end-of-line time offset
#
flag1: PPS enable
#
flag2: PPS direction (0 == rising edge, 1 == falling edge)
#
flag3: Use kernel PPS clock discipline
#
flag4: Obscure location in timecode
offet : 30ms (30100µS) jitter 10ms (10000µs)
ppstest works
but i don't understant with i can't get 1µs precision as if PPS kernel mode doesn't work
please help !!!! i'm a newbie and i need 1PPS and 1/10µs presision with linux and GPS sure electronics Board.
Thanks












 		 	   		  


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