[ntp:questions] Re: 1pps signal,20us width

Piotr Trojanek ptrojane at mion.elka.pw.edu.pl
Sun Nov 21 13:56:39 UTC 2004

On 2004-11-03, Fei Wu <fxw115 at yahoo.com> wrote:
> Is it possible for me to set the bit rate to 56K? So
> 20us pulse can be treat as one bit width; therefore,
> ntp can lock the edge of pulse?  

I had similar problem with 1PPS on TTL voltage levels
and only 10uS width. It was working fine connected
to DCD pin of RS232 port (FreeBSD-4.9) of my desktop

It was not working with the same OS but diffrent motherboard.
I was trying tu use even 115200bps setting of the serial port,
but this did not help.

Finally I have connected HCT123 chip between 1PPS and
RS232 port, and changed the width of the pulse to 100mS.
Now It work fine.

Piotr Trojanek
Faculty of Electronics and Information Technology
Warsaw University of Technology, Poland

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