[Trlog] CI-V interface for 756PROII and voltage

[VR2BrettGraham]

EA6BF said:

>I have recently bought a G4ZLP CI-V interface that I received today. I have
>tryed with my 756PRO2 with same baud rate in PC and radio and address
>converted to decimal (64h = 100), thank?s to you guys. But.....it doesn?t
>works...! I have noted that the voltage at 3.5mm mono jack is at 0.656V, and
>negative (shield) is at center connector and positive at other side. I
>normally do possitive at center and shield at the side, but maybe this is
>the way here. I builded an interface some weeks ago without success, also
>the voltage showed in the jack was less that 1V. I am using an old PC here,
>but it is supposed to work, I use it for contests and some logging, but yes,
>I haven?t use the SERIAL port, but this PC has worked with CAT at EA6IB last
>year and worked.....Any suggestions, measurements, tips, etc...are
>welcome..! I?ll keep on trying, do not give up..!

The CI-V bus is positive, so if you are really seeing negative
something from the interface, you might have a bit of a
problem.

Since even computer serial port not recently been seen to
be working, I would be tempted to:

1. Short pins 2 & 3 of serial port together, fire up a
terminal program & verify that you can see what you
type (proves serial port okay).

2. Then connect CI-V interface & again check with
terminal program to see what you type comes
back (CI-V effectively shorts those two pins together
on the radio side).

3.  If all okay to this point, then connect radio to
CI-V interface (assuming CI-V "transceive"
function is turned on) & watch for data coming (again
using terminal program) from the radio after spinning the
VFO knob.  If you see something, then radio at least
talking - if can talk probably can listen, leaving you with
things like baud rate & addresses.

73, VR2BrettGraham