![]() The converter is normally powered by the host computer's RS-232 port. The main circuit consists of little more than 2 diodes, 5 capacitors, the MAX-232 IC chip, and a voltage regulator chip. I chose to assemble the unit in a metal enclosure for RFI sheilding. The 2 photos below show the prototype converter I built. ![]() Unfortunately, Icom charges an exorbitant amount of money for what is basically a glorified RS-232 to TTL level converter! However, using the MAX-232 integrated circuit, such a converter can be easily built for under $20. ![]() All in all, it's quite elegant in it's simplicity. Multiple devices may connected across the CI-V port in parallel, as long as each device is set up with a unique hex address. When the line goes low, the other devices see this as a BUSY indication, allowing the single DATA line to offer some amount of basic flow control. As long as the DATA line is high, any device can initiate communication by pulling the line low and sending the Icom attention command (FEFE). The DATA line is held high when there is no traffic. The single wire consists of a communications line (DATA) and a ground reference (GND). ![]() ICOM's CI-V protocol is based on a relatively simple bi-directional, single-wire TTL level signaling system. ![]()
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