Build Your Own CI-V Interface for Icom Radios

Be sure to visit our Icom USB CI-V Interface page.

Interested in interfacing your computer to your Icom radio(s), but not interested in paying Icom's high price for an interface? Well, here's how you can build your own interface for $5 or so, in about an hour.

              +12V
              |
              |
             _|(14)   IC1 MC1488 Line Driver
             | \      
        (2)  |  \  (3)
Icom  _______|   \______ Receive data (RS232 pin 3)
             |   /
             |  /|(7)
             |_/ |
           (1)|  |
              |  |
              |  |
           -12V  GND

               +5V
                |
                |
               _|(14)   IC2 MC1489 Line Receiver
               | \
           (1) |  \  (3)
 RS232 pin2 ___|   \______ Icom
               |   /
               |  /
               |_/ 
                |(7)
                |
                |
               GND

RS232 Pin 7 -------GND

Yes, you do connect the two signals marked "Icom" together, they go to the tip of the 1/8" plug, ground goes to the sleeve.

How It Works

Icom's CI-V interface uses TTL level signals. One pair is used for both transmitting and receiving data. IC1 Takes the data received from the radio (TTL, 0-5 volts) and converts it to an RS-232 signalling standard (+/-12V). This is then sent to the computer. IC2 takes the RS-232 level signal from the computer, and converts it to TTL level. In theory, only three RS-232 wires need to go to the computer: Pin 2 Tx Data Pin 3 Rx Data Pin 7 GND Often, you'll need to tie the appropriate handshake lines, or the computer will refuse to send data. Generally, just tying RTS/CTS together (pins 4 and 5) and DSR/DTR together (pins 6 and 20) will work. Please note that I have specified the pin numbers for the standard PC 25 pin serial port. The 9 pin (AT style) port has a different pinout, check your documentation. Macintosh users: Use a standard modem cable (which goes from the Mac's 8 pin mini-DIN to the standard 25 pin serial connection). You could simplify things by using a chip such as Maxim's MAX232. This chip only requires +5V, and contains both the line driver and receiver. Throw all this in a box, add some 1/8" jacks and a serial cable, and you'll have the functional equal of Icom's CT-17 Level Converter.

If you have a Mac, plase check out Black Cat Systems which contains demo copies of my Macintosh software for science and radio applications.

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