[email protected] said: > The timing message ends 40-45 msec after the 1PPS pulse. Interesting that > is it is not a fixed or random delay. It seems to be quantized to 40, 45, > or occasionally 50 msec. The delay does not change randomly, but seems to > settle on a particular value for extended periods. Heather now assumes it > is 45 msec. Not sure how much of the message jitter is from the Tbolt or > Windoze.
I'm running NTP on Linux. I'm seeing about 10 ms of jitter. That's after all of NTP's filtering. My stuff changed when I turn on the low-latency flag for that serial port. I didn't say "got better". The graph looks cleaner. I think it removed some of the high frequency jitter. The remainder reminds me of the hanging bridges - very hard to filter out. > Anyway it looks like Heather can keep your Windoze clock fairly accurate... > probably within a Windoze timer tick (or two). One could probably do > better by hooking the 1PPS signal to a modem control interrupt (Carrier > Detect?) but that opens up a fresh can 'o nematodes. That's the way to go if you want good timing. Beware, there is a big rat-hole in making computers keep good time, and it's got "time-nuts" written all over it. DCD is the common pin for that purpose. Some OSes support other pins. Pin 1 (DCD) on the TBolt isn't connected to anything. I added a jumper over to the PPS connector which is conveniently nearby. More news when the self-survey finishes. (Which may take a long time since my antenna setup is poor.) Pins 6 (DSR) and 9 (RI) have traces that are visible. One goes to an empty resistor. The other goes to chip marked "232". I assume it's a level converter. If so, it's an output pin. All the documentation I've found says "Not used". Maybe I mistraced someting. -- These are my opinions, not necessarily my employer's. I hate spam. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
