[ntp:questions] Sure GPS - PPS not working

David Taylor david-taylor at blueyonder.co.uk.invalid
Mon Dec 9 16:58:42 UTC 2013

On 09/12/2013 11:30, Chris North wrote:
> David,
> I have managed to fix it, and it was a bit unexpected. When I first installed the Sure, I used a USB connection and got it working OK. I then used a Serial-USB adapter and was pleased to find that it passed DCD and that PPS was working. The jitter was rather high, though - about 0.3 mS. I bought a 2-port serial PCI card and a serial cable, and immediately had a massive improvement in performance. Recently, however, I found that PPS had stopped working, as you have seen above.
> What I think happened was this: when I plugged in the new card it used the standard Windows serial.sys, which I replaced with serialpps.sys. Now this card is part of a range of multifunction cards that offer various I/O interfaces. At some time Windows Update probably found the manufacturer's drivers and installed them (automatically, or as an option that I just accepted). The new driver ignores serial.sys and has its own software. So I poked around in the registry and changed the ImagePath for one of the card's new services to point to serialpps.sys. This seems to have fixed it. As I don't use the COMn ports for anything else, I won't worry about possible side-effects.

Good news, Chris.  I'm glad that my suggestion of looking at the driver 
tree may have helped.  Quite possibly the same "update" issue happened 
to me when I went from Windows 8.0 to 8.1, except that it wasn't quite 
as obvious as a normal monthly update.  I better try and document that 
somewhere - if I haven't already.

Web: http://www.satsignal.eu

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