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CI-V simplified by modern tech for Icom radio control

There’s a simple eighth inch jack on the back of most Icom radios that provides a communication interface for control purposes. If you look around for how to tie this into a computer, most of what you’ll find is about converting to a standard RS-232 serial port. That is soooo old tech! I like what Guy Dickinson says about this.

Googling around, we found lots of level converters for RS-232 serial ports, but very little with USB in mind. In addition, most of the circuit designs for homebrew cable assemblies were quite complicated, and generally speaking, published in about 1992.

It turns out that the Icom CI-V interface is TTL-based, with the TX/RX cables bridged together, with a ground reference on the sleeve of the 3.5mm connector. Given the popularity of Arduino and similar chipsets that require a TTL serial interface to program and operate, we figured we could do better with a prefabricated USB-TTL cable like the TTL-232R-5V from FTDI. It turns out the resulting build is stupid-easy.

Prefab USB to serial cables are available for under $5. They sport a popular chip like the Prolific PL-2303HX Edition (Chip Rev D) USB to Serial Bridge Controller or the Silicon Labs CP2102/9 sinlge chip USB to UART bridge. See below – gpsd and finding the GPS via USB for using one of the cables with a GPS module.

As Guy notes, this is a “stupid-easy” method using cables originally intended for the maker crowd to program their microcontrollers. It is also ‘stupid-cheap’ and it is also open ended with the ability to add PTT or whatnot. If isolation is a concern, you can add an optoisolator or other protections. This is right down the maker alley and there are inexpensive breakout boards for optoisolators, relays, and whatnot. It’s be easy to make your own super duper rig control with, say, a small usb hub, usb to audio dongle, and some other modules.