[ntp:questions] First attempt GPSD/PPS ->NTP time server

Rob van der Putten rob at sput.nl
Tue Jan 29 17:15:22 UTC 2008


Hi there


root wrote:

> No GPS NMEA should not do that. The length of the sentence is almost fixed 
> length, so the timing on it should vary by perhaps a few msec, as you found, 
> certainly not by seconds. It sounds like you have troubles. 
> 
> You could try using minicom ( assuming you are on Linux) to look at the output
> on the serial port.

PPS is tied to DCD. So online is off 90 % of the time.
With the following circuit you can configure the GPS receiver;

Garmin		Minicom

Male    	Female
		9P	25P

RXD-----RXD	2	 3

TXD-----TXD	3	 2

GND-----GND	5	 7

       +-DCD	1	 8
       |
       *-DTR	4	20
       |
       +-DSR	6	 6

       +-CTS	7	 5
       |
       +-RTS	8	 4

SH------SH

> The GPS sentence should certainly be able to pull you into the second range
> very easily.
> Anyway use some serial port terminal program to read what the gps is sending and how often. 
> (Remember at 4800Bd, it takes about 2 msec to send each character.

My Garmin was sending to much data, sending a NMEA sentence once per 
second. So I put '$PGRMO,,4<CR><LF>' in a file and send it to the Garmin.
Now it's at six lines per second; GPRMC, GPGGA, GPGSA and three GPGSV 
lines (plus one PGRMT per minute).


Regards,
Rob
-- 
When the Iron Curtain fell, all of the West rejoiced that the East
would become just as free as the West. It was never supposed to be the
other way around. (Rick Falkvinge)




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