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Re: [gpsd-dev] Problem with PPS detection - using Centos 7 and gpsd dev-

From: Mick Durkin
Subject: Re: [gpsd-dev] Problem with PPS detection - using Centos 7 and gpsd dev-3.19a
Date: Mon, 14 Jan 2019 13:27:20 +0000 (UTC)

Hi Gary,

Here is a follow-up to your first mail.

1) The Perle driver.

I could attach this, but it is a largish source RPM, so it may be better if you 
access it directly from Perle's website. I CAN forward it if you prefer. It is 
available on Look under the following:-
      Serial & Parallel Cards
         SPEED LE Serial & Parallel Cards

There you will see the Linux Source RPM version 3.92. I will compare this with 
the standard driver and look at the references you gave me.

2) Compile gpsd without kpps.

This took a bit of doing, but eventually I was able to make it compile by 
modifying SConstruct not to set HAVE_SYS_TIME and, as a result, pacifying 
complaints in "timehint.c" and "gpsmon.c". I don't think this made any 
difference to the main body of gpsd, as it ran nicely and detected my PPS via 
the "ioctl (TIOCMIWAIT)" path.

This proves your conclusion that the Perle driver doesn't handle kernel PPS. I 
attach a short file showing the changes I did to hack KPPS support out and then 
a log of the successful run detecting the PPS via TIOCMIWAIT. I included the 
messages from "NTP:" this time as it shows timevalues with -20 and -30 
precision, so it looks like gpsd is shipping both sets of data to ntp.

I will look into the dirver code and if I can find a fix, I will come back to 

Thanks for the support.


Attachment: changes_to_suppress_kpps.txt
Description: Text document

Attachment: pps_test_suppress_kpps.txt
Description: Text document

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