This post is quite old! Check out the updated version of this interface
Turns out working the the Icom CI-V interface really isn’t all that difficult, I am using the above with my Icom IC-728 and Ham Radio Delux (HRD). The CI-V interface combines both the TX/RX pair on the tip and grounds via the sleeve, the ring is not connected but must be present for the interface to work with some rigs. The cable I use is a TTL-232R-3V3 UART adapter from RS* and also provides the additional pins (CTS / RTS) which I will be using to trigger the PTT on my rig for my PSK31 build. Cheaper dapters that only have the TX/RX pairs could be used instead, but make sure the signalling voltage is 3.3v .
*A cheaper cable is available via amazon: USB to TTL Serial Cable