On Dec 30, 1:36 pm, dhavey <dha...@gmail.com> wrote: > On Dec 30, 9:39 am, David Woolley > > > > <da...@ex.djwhome.demon.co.uk.invalid> wrote: > > Unruh wrote: > > > Garmin defines the leading edge as the transition from 0V to 5V on the PPS > > > line. Now serial has two levels -12V and +12V. with capacitive coupling, > > > There's no capacitive coupling; it is assumed that the transmission line > > and load behave as capacitive, but that is in parallel. > > > The transition region for RS232C is -3V to +3V into 4 to 5k. > > > > the garmin signal would be something like -2.5V to 2.5 V which really is > > > However, the expected hysterisis is in the 10s to 100s of mV range, and > > the actual threshold for control signals is supposed to be above zero, > > such that zero volts will give an unambiguous off state. > > > In practice, therefore, with real world RS 232 line receivers, there is > > no problem in feeding from TTL levels, as long as the cable is short > > enough to avoid ringing. > > > > way out of spec for the serial port. (Or with the typicallysmall duty > > > cycle, more like -1V to 4V) > > time.qnan.org seems to indicate that > flag2 0=pps edge on assert > or High to Low > is standard behavior for GPS devices.
I don't see much difference in offsets between the machines either way: +192.168.0.29 .GPS. 1 u 3 16 377 0.090 3.084 0.254 *GPS_NMEA(0) .GPS. 0 l - 16 377 0.000 -0.276 1.722 +192.168.0.28 .GPS. 1 u 16 16 376 0.001 -2.921 0.124 *GPS_NMEA(0) .GPS. 0 l 15 16 377 0.000 0.286 1.399 Something else must be wrong. _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions