Icom CI-V USB/TTL Rig Cable Design Using the FTDI Chipset

July 25th, 2011 § 19 comments

I spent some time this weekend with the fine folks over at NYC Resistor hacking on some ham radio related stuff. We took a crack at a USB CI-V interface for an Icom radio. 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.

Here’s a diagram of the resulting assembly, for those who are searching for how to do this:

We turned out to require a stereo Ring-Tip-Sleeve connector rather than a mono two-conductor one, despite much documentation claiming the contrary. Your mileage may vary.

If necessary, one could also use the RTS/CTS contact-closure as a push-to-talk switch setup, which most of the popular ham radio software packages support. The total cost of this assembly is roughly $20, which is how much the cable costs. To cut costs even further (down to about $5), you could hack this together using the bare FT232RQ chip which you can get from Mouser for $4.95 as of this writing. In any case, this is a pretty massive improvement over the $60 that Icom likes to charge for the equivalent.

The drivers are available for all major platforms and are bundled in the Linux kernel already so the additional software needs are minimal for this over a ‘traditional’ RS-232 cable. We tested this on Mac, Linux, and Windows with perfect results.

§ 19 Responses to Icom CI-V USB/TTL Rig Cable Design Using the FTDI Chipset"

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