[ntp:questions] NTP NMEA driver

rajputajay84 at gmail.com rajputajay84 at gmail.com
Thu Feb 13 10:44:03 UTC 2014


On Thursday, 6 February 2014 16:35:15 UTC+5:30, Charles Elliott  wrote:
> The config file should have this format
> 
> 
>  
> server 127.127.20.1 mode 65 minpoll 4 maxpoll 4 prefer
> 
> fudge 127.127.20.1 time2 0.363352  
> 
> fudge 127.127.20.1 flag4 0

Hi Charles Elliott,

i have corrected mode 0 to mode 1 as i am using only NMEA output of gps receiver at 4800 baudrate.
> 
> 
> 
> 
> 
> Charles Elliott
> 
> -----Original Message-----
> 
> From: questions-bounces+elliott.ch=verizon.net at lists.ntp.org
> 
> [mailto:questions-bounces+elliott.ch=verizon.net at lists.ntp.org] On Behalf Of
> 
> rajputajay84 at gmail.com
> 
> Sent: Thursday, February 6, 2014 4:58 AM
> 
> To: questions at lists.ntp.org
> 
> Subject: Re: NTP NMEA driver
> 
> 
> 
> Dear Sir,
> 
> 
> 
> I am trying to synchronize AM335x processor based linux 3.2 with Motorola
> 
> GPS receiver using its Serial based NMEA frame and 1pps signal. I have
> 
> connected nmea frame to ttyO1 port. I am using buildroot based filesystem
> 
> for NTP configuration. NTP version used is 4.2.6p5. 
> 
> 
> 
> I have configured ntp.conf file for nmea driver 20 for nmea and 1pps
> 
> options. (refer:
> 
> http://www.eecis.udel.edu/~mills/ntp/html/drivers/driver20.html)
> 
> 
> 
> # Ajay - for nmea driver 20
> 
> server 127.127.20.0 mode 0 minpoll 4 maxpoll 4 prefer fudge 127.127.20.0
> 
> flag1 1 flag2 0 flag3 1 time2 0.500.
> 
> 
> 
> time2 is set to 0.600 since delay between 1pps signal rising edge and end of
> 
> nmea frame is approx 500ms.
> 
> 
> 
> i am issuing below command for nmea driver 20 before starting ntp service:
> 
>  
> 
> ldattach pps /dev/ttyO1.
> 
> 
> 
> [   94.658905] pps_core: source OMAP-SERIAL1 got cdev (253:0)
> 
> [   94.658935] pps pps0: new PPS source OMAP-SERIAL1
> 
> [   94.663787] pps pps0: source "/dev/ttyO1" added
> 
> 
> 
> 
> 
> 
> 
> Also, while kernel booted it already had registered pps for kernel line
> 
> discopline as per below message:
> 
> [    0.181427] pps_core: LinuxPPS API ver. 1 registered
> 
> [    0.181427] pps_core: Software ver. 5.3.6 - Copyright 2005-2007 Rodolfo
> 
> Giometti <giometti at linux.it>
> 
> 
> 
> 
> 
> ln -s /dev/ttyO1 /dev/gps0 (for linking ttyO1 to /dev/gps0 for nmea driver
> 
> 20) (as per http://www.eecis.udel.edu/~mills/ntp/html/drivers/driver20.html)
> 
> and
> 
> ln -s /dev/pps0 /dev/gpspps0 (for linking pps0 to /dev/gpspps0 for nmea
> 
> driver 20) (as per
> 
> http://www.eecis.udel.edu/~mills/ntp/html/drivers/driver20.html)
> 
> 
> 
> Now, when i start the ntp service, i get below output for ntpq -p command:
> 
> 
> 
> 
> 
>      remote           refid      st t when poll reach   delay   offset
> 
> jitter
> 
> ============================================================================
> 
> ==
> 
> *GPS_NMEA(0)     .GPS.            0 l    4   16  377    0.000  4526.86
> 
> 1269.17
> 
> 
> 
> Problem: Though i have configured my ntp.conf file for nmea and 1pps both
> 
> (using flag1 1), i do not see any entry for PPS in ntpq -p command.
> 
> if kernel has registered pps0 as pps source, why there is not PPS entry. I
> 
> have connected pps signal of 3.3v level to my dcd pin of ttyO1.
> 
> 
> 
> Also, the offset in NMEA output continously increases insteed of reducing.
> 
> 
> 
> Thanks & Regards,
> 




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