The IC735 CI-V Interface

Every once in a while, I get the urge to build a computer interface for my IC-735. This isn’t as easy as it sounds as the Icom CI-V interface is not a standard RS-232 type interface. The signal levels are TTL-level signals and it’s a two-wire interface.

The last time I got the urge, I did a web search and came up with the following:

  • The Icom CI-V Interface. This is a complete online manual to the interface and the software driving it. The page on CI-V level converters has links to many different circuits, including a relatively complicated one using the MAX232 chip.
  • G3VGR Icom CI-V Interface. This is a nice little circuit using a couple of 2N2222s, two diodes, and four resistors.
  • THE ICOM CI-V COMPUTER INTERFACE. This is an article written in 1986 describing the CI-V interface. It not only describes the physical interface, but the command set as well. One thing I didn’t know–the IC-735 was the first rig to use this interface.
  • Ham Radio Controller Programs. This page contains links to a bunch of rig control programs and information, not solely for the IC-735.
  • 801SCAN. 801SCAN is actually a control program for the R7000, R7100 or R9000 receivers, but this page also has a circuit for a RS-232 to CI-V interface. This circuit uses a 74HC04 IC. Do not try using a 7404 in place of the 74HC04. Also, I would advise against using his construction technique, to wit, “Chop the unused pins off of the 74HC04 and glue it to one side of the DB-25 shell with super-glue…” This is NOT good amateur practice :) .
  • CI-V Icom/PC Interface OK1DUO. This circuit uses a MC145407 IC, which I’ve never heard of. It also requires a couple of zener diodes. It’s certainly much more complicated than the G3VGR circuit above.
  • Icom CI-V Interface Design by K4PWO.This design uses a MAX233 RS-232 interface IC and a 78L05 voltage regulator. There is also a sample PC board design. It’s a nice design, but I don’t think it will fit in a DB9 shell.

It’s odd that I didn’t find any that use optoisolators. I’d think that doing this with optoisolators would be ideal. I guess the problem is that the rig doesn’t supply any power since it’s only a two wire interface (signal and ground). So, even if you use an opto, you won’t be isolated because the interface is supplying the voltage.

Of course, I could go out and buy an interface, but I think any self-respecting ham should build something like this that is so simple.

Comments

  1. Just thought you might want to know that the link to the 801 scan page doesn’t work.

    Eric.

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