G3VGR Icom CI-V Interface      

Icom appears to delight in charging outrageous prices for all transceiver accessories, so many Hams improvise instead. A few circuits have been published for CI-V interfaces, most of which use the MAX232 IC.  Here is a very simple CI-V interface, originally described by OK2WY.  I've made small changes to the modem control signals connections. Although the circuit doesn't conform exactly to the RS-232 specification, it does work well and has the advantage of being easily constructed inside a 9 pin D-type shell. Please note that the resistor value 4K7 means 4700 ohms.  The transistor types are not critical, I just happen to have plenty of 2N2222As.
I've used this interface on various PC's and also Dell Latitude Notebooks with both an IC735 and IC706MkIIG. No problems have been experienced even at 19200 baud with the IC706. It has also worked successfully when using a USB/Serial adapter from a notebook.  If a PTT function is required from the COM port, pin 7 (RTS) can be used to provide this facility.
The circuit is powered by DTR (pin4).  I experienced some problems with YPLog using this power source. If YPLog is configured to use PTT from either the Parallel port or a different serial port from the one used by the CI-V Interface, the program drops the DTR signal, resulting in no power to the interface.   This is easily resolved by powering the circuit from RTS (pin 7) instead of DTR (pin4). To test and/or debug the interface, I would strongly recommend using AA6YQ's CI-V Commander program.
I have also used this interface to program my Yaesu FT50R. Only a change of connector to a 4 pole minijack plug was required. Probably the interface can be used with other HTs, although I have not tried it.


Note:   If you intend using this interface with a USB/Serial adapter, beware of a possible issue with many of the cheap adapters available on eBay. Many of these use counterfeit Prolific PL2303 chips. When Prolific discovered this, they amended their drivers to detect counterfeits. The drivers supplied with Windows7 & Windows8 will result in an "Error 10" when they detect the counterfeit chip. The workaround is to use the drivers supplied for Vista.

Although I have successfully used the interface with a serial-USB adapter, I have seen USB CI-V cables from China at very cheap prices on eBay. Consequently, if your PC/Laptop has no serial ports, it's hardly worth the effort of building this interface nowadays. So just get a USB interface from eBay.

Disclaimer: Although I have tested and used the above circuit on my own IC735 and IC706mkIIG with no problems, I do not make any representation or guarantee that this circuit will function, nor do I accept any responsibility whatsoever for any damage or malfunction arising from the use of this circuit.

Here are some links to software for use with CI-V controlled Icom rigs: 
CI-V Test by DF4OR  - Freeware program to test CI-V bus
CI-V Commander by AA6YQ  - Freeware program to control Icom rigs and monitor CI-V bus
RadioComm by KE7ZZ  - Careware program to control and load memories of Icom rigs
YPLOG by VE6YP  - Shareware Icom Rig control and logging program
Ham Radio Deluxe by HB9DRV  - Bloatware Icom control program