[time-nuts] PRS 10 and serial port communication

[Jim Harman]

Actually a null modem is just the device that interchanges the connections,
Rx to Tx and sometimes DSR to DTR and others. The inverters are needed in
this case to convert zero or negative voltage levels to positive and vice
versa.

On Fri, Mar 4, 2016, 6:00 PM Artek Manuals <Manuals at artekmanuals.com> wrote:

> The "inverter's" went by the jargon name of "null modem" back in the day
> ...if you google "null modem" you will find the wiring diagrmas for
> rolling your own with a couple DB9 connectors.... I have to use the null
> modem adapter  when using a standard off the shelf serial cable with my
> z3801A as well
>
> Dave
>
>
>
>
> On 3/4/2016 2:26 PM, Philip Zahariev via time-nuts wrote:
> > As already tell you I have success with inverters and now can monitor
> state of PRS 10. Attached send current status for comments. Any help
> appreciated.
> > Best regardsPhilip
> >
> >
> >        From: Hal Murray <hmurray at megapathdsl.net>
> >   To: Philip Zahariev <philip_zahariev at yahoo.com>; Discussion of
> precise time and frequency measurement <time-nuts at febo.com>
> > Cc: hmurray at megapathdsl.net
> >   Sent: Friday, 4 March 2016, 11:43
> >   Subject: Re: [time-nuts] PRS 10 and serial port communication
> >
> >
> >> As I already write PRS10 is configured as serial communication. With
> >> oscilloscope I can see serial signals, but when enter this signal in
> >> computer with TTL level USB2serial converter all information is
> repeatable
> >> character unknown for me and not as described in manual.
> >
> > You may need to add or remove an inverter in there.
> >
> > Most serial ports on microprocessors and USB to serial chips are
> expecting a
> > TTL to RS232 level shifter and the standard level shifter chips all have
> an
> > inverter.  If there are 0 or 2 inverters it should work.
> >
> > Some GPS modules don't have any level shifter.  Some devices include an
> > inverter but not the level shifter.  That doesn't meet specs but it
> generally
> > works if you connected it to a real serial port (with level shifter).
> >
> > I would connect a scope to the output side of the USB to serial chip and
> send
> > it occasional characters and use that as a reference for what a
> character is
> > supposed to look like.
> >
> > Then look to the input side and see if it looks similar.  In particular,
> > verify that the idle level is the same.  Then check the baud rate and
> parity.
> >
> >
> >
> >
> >
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>
> --
> Dave
> Manuals at ArtekManuals.com
> www.ArtekManuals.com
>
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