Outline

CI-V. stands for Computer Interface, is Icom’s name for its rig interface to a computer or to another rig. Other manufacturers such as Yaesu refer to this as CAT (Computer-Aided Transceiver). Each manufacturer typically implements its own version. Icom kept the same protocol across its many transceivers, while Yaesu generally wrote a new protocol for every new radio.

A CI-V interface is a piece of hardware that connects the radio and the PC, allowing them to communicate with each other. The CI-V interface provides the required voltage levels for CI-V (5V TTL; Mark +5V Space 0V), RS232 (Mark -V, Space +V), or Serial on USB. The CI-V connections may be connected in parallel. The actual communication is between the radio and other radios / devices or the software on the PC. Functionality depends on the radio’s capabilities and what features the software writers included in the CI-V program.

Hardware Interface

Icom CT-17, a discontinued Icom product, allowed connection of a CI-V bus (four parallelled ports – physically 3.5 mono jacks) to a computer RS-232 port, either DB 9pin or 25 pin.

CI-V to USB Cable The CT-17 functionality may be provided by the schematic below. This same schematic may be used for a CI_V to USB cable by replacing the parallel 3.5mm phone jacks with a cable to a 3.5mm phone plug. Active to tip and ground to body.

Late model radios provide serial on USB interface and sometimes 3.5mm mono CI-V interface as well. Depending on the application, these interfaces may communicate independently or may be linked so the communications on one interface is also on the other.

PTT Extender Interface

The PTT Extender provides an independent open collector output for each VHF / UHF band of the IC9700, IC9100, and IC910H radio. The CI-V serial protocol for the PTT Extender is 19200, 8, N, 1. The radio must be set to 19200 baud or auto. Other baud rates (4800 & 9600) may be provided on order.

The CI-V interface to the Arduino Nano processor in the PTT Extender has proven to be rugged and reliable.

A CT-17 or similar should not be used to connect other devices / personal computer to the “remote” port on the Radio where a PTT Extender is used. Connecting other devices / personal computer via a USB interface and CT-17 on the USB port will minimise conflicts on the CI-V bus.

References

Making the CI-V Connection – On All Bands
CI-V Programming Tutorial KB3HHA – Seth Cohen
PTT Extender Info Sheet – VK4AMG
IC9700 PTT Extender Assembly Manual – VK4AMG
CI-V and CT17 Interface – VK4AMG pdf