[ICOM] One CI-V, two serial connections?

[Mike Mellinger WA0SXV]

I've not had to debug CI-V issues for a long time but this one is
interesting.  I did look at the N2VZ website to see what his instructions
are.  Interestingly enough, the manual on the site says to set the baud rate
to 300.  Since your installation worked fine at 4800 without the laptop I
think that we can dispense with that particular setting.

N2VZ is correct -- you can use a stereo headphone "Y" to connect the laptop,
the radio, and the tuner.  CI-V just uses tip and sleeve so the additional
conductor ("ring") doesn't matter.  I do this to connect a 7800, PW-1, BigIR
control box, and the desktop.  Works just fine.

Some questions:

1.  the N2VZ tuner sends a Morse S if it doesn't like the CI-V data.  Do you
get the S when it is mistuning?
2.  what are you using for the CI-V to laptop interface?  Many interfaces
are powered by the laptop itself and may have problems with more complicated
CI-V connections?

My guess is that you're having problems with clashes between the Tuner
interrogating frequency and the laptop interrogating.  The tuner may not
correctly handle this and get confused.  All other things being equal I
think that I'd talk to N2VZ.  He may have designed this interface assuming
that nothing except the radio will be on the CI-V bus.  Also, when he
changed from 300 to 4800 baud he may not have changed the circuitry to use
small bypass capacitors on the CI-V line.  This will make a mess of the data
pulses and onlys get worse as additional items are connected. I saw this on
some of the early CI-V to serial converters -- big bypass capacitors that
worked fine at 2400 baud were a disaster at 19200.

The other thing that will cause this is if anything on the CI-V line,
whether the laptop software, the tuner, or the radio is set to baud rate
"AUTO".  But from your post this doesn't seem to be the case.


73,
Mike WA0SXV


>From: Michael G. Carper <mike at wa9pie.net>
>Subject: [ICOM] One CI-V, two serial connections?
>To: "'ICOM Reflector'" <icom at mailman.qth.net>
>Date: Saturday, July 25, 2009, 2:38 AM
>
>
>Has anyone had any luck getting two serial devices to talk to a single
CI-V?
>
>
>
>I've got an IC-706MkIIG in my truck with a Turbo Tuner (this has a
>2-conductor 1/8" male connector on it that plugs into the CI-V port).
>
>
>
>I've also got a laptop with a CI-V cable (that has a 3-conductor 1/8" male
>connector on it that plugs into the CI-V port).
>
>
>
>N2VZ told me to get a headphone splitter (like you'd use for an iPod) and
>connect both to the CI-V port.
>
>
>
>I did this and it kind-of works.  Both connections have to be at the same
>baud rate (the Turbo Tuner is 4800 baud, so I make the computer connect at
>the same rate).
>
>
>
>The issue is.
>
>
>
>The Turbo Tuner gets confused and ends up taking the antenna the wrong
>direction to tune.  When only the Turbo Tuner is plugged in, it works just
>fine.
>
>
>
>Thoughts?
>
>
>
>Mike, WA9PIE
>