[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
computer.

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



More information about the questions mailing list