Exactly. And, as someone else pointed out, you then need to delay it 900 ms to put it back in the right place, which would take a lot of gate delay. This is time nuts after all...
On Sep 8, 2013, at 11:08, Chris Albertson <[email protected]> wrote: > You only need ONE inverter gate. > > The purpose is the flip the pulse. The MAX 232 chip flips the logic > once which works fine for the data but you need to flip the control > lines (maybe if the GPS reciever did not already do this for you.) > > Flipping the PPS has the effect of moving the pulse by the length of > the pulse so one gate in this case will move the pulse by 100MS. > > On Sat, Sep 7, 2013 at 9:22 PM, Bob Bownes <[email protected]> wrote: >> 100ms is an awful lot of 'inverter gates'! >> >> On Sep 7, 2013, at 23:15, Chris Albertson <[email protected]> wrote: >> >>> With RS232 the data uses negative logic (low is "1") and the control >>> lines use positive logic (high is "1".) That is, a control line is >>> "asserted" when it is at logic 0, a positive voltage. >>> >>> Some one at one time must have thought this made sense. >>> >>> The good news is that a mistake is easy to detect and fix. If the >>> pulse is 100MS long and you have it inverted then your time will be >>> off by 100MS. When you are designing the board put in some extra >>> inverter gates >>> >>> On Sat, Sep 7, 2013 at 7:15 PM, Mark Sims <[email protected]> wrote: >>>> I got in those Adafruit GPS boards. They are a very nice little GPS. >>>> VERY sensitive. I could get good lock indoors on my (windowless) kitchen >>>> floor. The house is 2 story, stucco with wire mesh in the stucco. I >>>> could also get lock in a restaurant that had a tin roof. We were far from >>>> any windows. >>>> The 1PPS signal is normally low and pulses high for 100 milliseconds. The >>>> RS-232 adapter board that I built feeds this into an RS-232 transmitter >>>> chip (MAX3232), so on the interface connector CD will be at +V and pulse >>>> down to -V. Is this what stock NTP likes? >>>> Also, I laid out the adapter board so it an accommodate a Trimble >>>> Resolution T or a Crius CN06 receiver. The Crius receiver uses a U-Blox >>>> NEO-6M receiver. They can be had for around $22 at HobbyKing. They seem >>>> to perform even better than the AdaFruit module. It looks like you will >>>> need to bodge a wire onto the TIMEPULSE pin to use it for 1PPS. >>>> _______________________________________________ >>>> 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. >>> >>> >>> >>> -- >>> >>> Chris Albertson >>> Redondo Beach, California >>> _______________________________________________ >>> 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. >> _______________________________________________ >> 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. > > > > -- > > Chris Albertson > Redondo Beach, California > _______________________________________________ > 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. _______________________________________________ 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.
