[ct-user] Serial interface & keying

Steve Dove Steve Dove <dsp@hifidelity.com>
Mon, 10 Jan 2000 17:15:57 -0500

Hi Ron,

Sorry.  I was a little too narrow;  the pins 4 and 7 previously mentioned refer
to the RTS and DTR pins on a 9-pin RS-232, as opposed to their counterparts on
a 25-pin.

It's actually quite common for the RS-232 / TTL level-shifting and inversion to
be done by logic inside the connector shell hanging off those two lines for
power;  it's truly 'orrible, but it works and beats having to independently
power another funny little box somewhere.  Whether such an arrangement would
have enough 'oomph' off just the RTS line, so freeing up the DTR line for
keying, will remain to be seen.

Certainly it seems as though Waldek has an 'all-singing, all-dancing'
combination along these lines happening already.

73,        Steve

Ron Stordahl wrote:

> Steve wrote:
> > Greetings,
> >
> > Some interfaces derive their supply from pins 4 and 7, precluding their
> use for
> > keying.
> >
> > 73,        Steve        W3EEE  /  G3YDV
> >
> >
> I don't see why that would get in the way.  For the CW keying interface you
> only need to get to pins 20 and 7.  And 7 is ground.  This is with the DB25
> connector.  Devices which derive power from the connector can still do so.
> Practically you would be using the port for both CW keying and rig control.
> I have never seen a rig control interface which derives its power from the
> RS232 port, but if its possible using pin 20 and 7 for CW keying will not
> get in the way.
> Ron N5IN

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