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.

--
Cheers,
David
Web: http://www.satsignal.eu

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