David Lord <[email protected]> writes: >David Lord wrote:
>> Below are values for offset and jitter from polls at >> 30 min intervals. >> >> BR-304 gps18x-lvc gps18x-lvc >> rmc rmc rmc+pps >> polls offset polls offset polls offset >> % n (ms) % n (ms) % n (ms) >> 50 90 9.23 51 27 0.07 54 76 0.002 >> 95 170 53.02 92 49 0.16 99 140 0.005 >> 99.5 178 435.84 100 53 0.20 100 141 0.006 >> >> Problem with BR-304 was lack of sensitivity and being >> unable to keep sufficient satellites in view, even >> though positioned with slightly better view of sky than >> the Garmin. >Oops again since I'd deleted jitter results as I'd missed sorting >them separate from the offsets. I'll put up a link to full table >of results, once I've finished trying various sources and also >settled on a reasonably consistent method for showing results. >These can even include those from when using chrony with >demand dial. >Anyway here are what I have so far: >Source Polls % offset jitter % offset jitter % offset jitter > @30min (ms) (ms) (ms) (ms) (ms) (ms) >(1) 141 54 0.002 99 0.005 100 0.006 >(2) 100 51 0.07 92 0.16 100 0.20 >(3) 179 50 9.23 95 53.02 99.5 435.8 >(4) 203 50 0.185 0.086 95 0.642 0.255 99.5 1.111 0.488 >(5) 53 50 0.165 0.070 95 0.621 0.246 99.5 0.673 0.333 >(6) 164 50 1.928 95 9.162 99 21.48 >(7) 174 50 0.847 95 2.548 99 6.548 Your number 3 is really terrible. That gps should not be delivering the time if it cannot lock on to enough sattelites. To deliver times that are 1/2 sec out is really pretty terrible. >VIA EPIA C3-600 >NetBSD 4.1/4.99x/5.0 then 5.0.1 >(1) GPS_NMEA gps18x-lvc + rmc + pps >(2) GPS_NMEA gps18x-lvc + rmc What is rmc? >(3) GPS_NMEA gs-br-304 + rmc >(4) SHM MSF + serial + "radioclkd2 -s timepps tty00:-dcd" >(5) SHM + PPS MSF + serial + "radioclkd2 -s poll tty00:-dsr" >(6) PARSE DCF77 + serial >(7) SHM DCF77 + serial + radioclkd2 + SHM > (not sure if using timepps kernel) >I didn't need serial-usb until very recently as all pcs here >except new netbook have serial port so a converter wasn't >needed when I tried out the GPS modules. I can't get converters >to work reliably from ttl out of either Conrad module or my >PPS extractor monostable both used for (5) above. I suspect a >ttl to rs232 conversion is needed or some simple hack. The problem is the interrupt. There is no way to deliver an interrupt to usb AFAIK. From what I understant, seems that there is random latency in the usb system as well. >David _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
