On Dec 30, 9:39 am, David Woolley <[email protected]> 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. _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
