I just completed testing of a Fox Delta ST1 computer interface for Yaesu G5400 and G5500 antenna rotators. I purchased this kit as a backup to our GS-232 interface for our ARISS school contact on July 4.
http://www.foxdelta.com/products/st1.htm
The kit was delivered quickly and kit completion took only a couple hours. It is available with either an RS-232 interface (which I purchased) or a USB interface (not tested). The only connections required are a serial port on the computer and a DIN-8 cable to the Yaesu controller. I used SatPC32 software but it is said to work also with Nova for Windows.
The only calibration required is setting the "OUTPUT VOLTAGE ADJ." for both Az and El on the Yaesu controller. The instructions say to set this voltage to 4.5V, but with this setting, the controller tried to rotate the antenna beyond its limit. I got a hint from WA8SME who programmed the PIC firmware to try increasing the calibration voltage slightly. I found a value of 4.7V worked properly.
The Az and El rotators are moved sequentially rather that simultaneously as does the Yaesu GS-232 controller. This slows down large movements in both Az and El, but since incremental movements are usually small, this should not matter much.
The unit performed as specified. The price sure beats the Yaesu GS-232 price.
Ron Parsons W5RKN