[ICOM] CI-V from USB - schematic ?

[Mike McCarthy, W1NR]

On 02/27/2012 12:45 PM, Jim Miller KG0KP wrote:
> Seems like if a ci-v is only 2 contacts that I can make one from one a USB
> to DB9 connector with an adapter or a pair of dikes and a mono plug ????????
>
> Comments ?
>
> I have a 705 MkIIG and it appears the CI-V is not functioning.  What is the
> SIMPLEST way to test it?  I have tried 3 USB CI-V cables.  I have tried
> another laptop.  No go.  I found another cable that is DB9 to mono plug but
> am not sure it is a ci-v cable.  Likely?  Comments?
>
> Thanks es 73, de Jim KG0KP
>
>

I have used this with success on a real serial port.

http://www.qsl.net/g3vgr/civ.html

As far as USB, you tie TTL levels TxD and RxD together at the tip of the 
mono connector. This is at the TTL levels before conversion to RS-232 
voltage levels. The diagram in the above link is for a regular serial 
port and converts the RS-232 levels to TTL.

I have found that the cheap USB cables from ePay use the Prolific chips 
and they just don't seem to work very well. There was an article on 
building one from FTDI chips in QST. You should be able to find this 
article on-line at the ARRL WEB site (if you are a member).

Of course, borrowing a known good interface cable will help too!

Mike, W1NR