Usually auto-sensing, but commonly set to 9600 or 19200 bps in software. Uses Hexadecimal framing starting with "FE FE" (Attention). CI-V Communications Interface-V, Reference Manual 3.2
lines are bridged to create the single-wire CI-V bus. A diode is placed between the cap T cap X
For those interested in learning more about the ICOM CI-V USB interface schematic, here are some top resources:
(typically 4.7kΩ to 10kΩ) is connected between the data line and +5V to maintain the bus in a high state when idle. Radio Side: A shielded cable terminating in a 3.5mm mono plug . The tip is the data line, and the sleeve is the ground. Simplified Wiring Diagram For those using a pre-made USB-to-TTL adapter (like those used for Arduino), the wiring is even simpler: Connect GND: Adapter Ground right arrow 3.5mm Plug Sleeve. Combine Data: Tie Adapter right arrow 3.5mm Plug Tip. Add Protection: icom ci v usb interface schematic top
| Approach | Key Components | Typical Use Case | | -------------------------------- | --------------------------------------- | ------------------------------- | | | 2N2222A, 2N3904, resistors, diodes | Older designs with native COM port | | MAX232 chip (RS-232) | MAX232, capacitors, DTR/RTS power | Direct replacement for CT-17 | | USB‑to‑TTL + buffer | FTDI chip or CP210x, 7417 buffer | Modern USB-native solution |
Run a jumper wire from that same pin to the 3.5mm jack Tip .
Do connect a standard RS-232 cable directly to an Icom's REMOTE jack. The radio's CPU expects 0-5V TTL levels. Applying RS-232's ±12V signals from a legacy COM port directly to the tip of a 3.5mm plug could permanently damage the radio's control circuitry. Usually auto-sensing, but commonly set to 9600 or
There are three primary "topologies" for a USB CI-V interface, each with its own schematic approach. The "top" view of your PCB or breadboard will depend entirely on which of these design philosophies you follow.
: Hams often bypass expensive official adapters by building their own using the MAX232 IC (for older serial ports) or the FTDI232RL chip (for USB). A classic "minimalist" schematic uses just three transistors and three resistors to combine those separate computer signals into the single CI-V bus. The USB Revolution
A good practice is to include a from the REMOTE tip to +5 V to ensure stable idle levels. A diode is placed between the cap T
Tie a from the 3.5mm Tip line to the 5V VCC line.
Every major Icom HF transceiver since the has featured a CI-V port on its back panel. This persistence turned CI-V into a "lingua franca" for radio enthusiasts, allowing a single interface design to work across decades of equipment. The Schematic: Elegance in "One Wire"
This guide provides a general overview of the ICOM CI-V USB interface schematic. Be sure to consult the specific datasheets and documentation for the FTDI chip and your ICOM radio for more detailed information. If you're not comfortable with electronics or soldering, consider seeking help from a qualified electronics enthusiast or a professional.
Set the (default 0x5E for IC-7000, 0x76 for IC-7300, etc.) in your software (e.g., WSJT-X, FLRig, HRD).
To maintain high data rates (up to 19,200 bps or 115,200 bps for newer rigs), high-speed optocouplers are required. Standard 4N25 or 4N35 optocouplers are too sluggish and will distort the data pulses.