[LinuxPPS] gps_nmea error

[Hal V. Engel]

On Tuesday 12 August 2008 11:02:51 am Ritter, Nicholas wrote:
> Ok...I loaded up minicom, I see the NMEA messages and I see minicom
> going online and offline which indicates (if I am correct) that DCD is
> being seen on the serial interface which means the serial interface is
> seeing the PPS pulse.
>
> We hooked up a scope to the electronics between the GPS unit and the
> serial port (which is just a breakout box containing the LED for PPS
> events and power to the GPS via a USB hookup, etc.) and we see the PPS
> pulse.
>
> I unloaded the pps related modules and reloaded them and noticed that
> the kernel does not see any PPS pulse unless the ktimer module is
> loaded, us this the way it should be?

ktimer is for testing when there is no device.   It is an artificial PPS 
signal that is generated when the ktimer module is loaded.   

You do have to run some userland tools before an actual PPS signal will be 
available.  This includes ppsldisc which needs to be running when you start 
ppstest and also when the ntp refclcok driver is started.

On my machine I also need some udev rules to do a setserial command for the 
serial port used for the GPS and the PPS signal and also to create some sym 
links so that these have the names the refclock driver is expecting.  I have 
the ppsldisc command embedded in the ntpd startup script.  There are notes 
about how to set this up on this list.

Documentation for this is not yet up on the LinuxPPS wiki.

>
> I think that until I can get the ppstest command to show output that
> represents an assert and a clear that my problem is in the kernel?
>
> [root at RMSQSN1001 pps]# ./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 1218564002.534427140, sequence: 114 - clear
> 0.000000000, sequence: 0
> source 0 - assert 1218564003.534412191, sequence: 115 - clear
> 0.000000000, sequence: 0
> source 0 - assert 1218564004.534427129, sequence: 116 - clear
> 0.000000000, sequence: 0
> source 0 - assert 1218564005.534419326, sequence: 117 - clear
> 0.000000000, sequence: 0
>
>
> Thanks Udo for the config example. I have confirmed that my GPS unit is
> set to 200ms.
>
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