Icom Ci V Usb Interface Schematic Top Link
PC SIDE (USB POWERED) │ RADIO SIDE (RIG POWERED) │ ┌───────────────────────┐ │ ┌──────────────────────┐ │ │ │ │ │ │ USB-to-UART │ │ │ 3.5mm MONO JACK │ │ Bridge IC │ │ │ (To Radio) │ │ (FT232RL / CH340) │ │ │ │ │ │ │ │ ┌───┐ │ │ TXD ───[1kΩ]───┐ │ │ │ ┌────┤TIP│ CI-V Bus │ ▼ │ │ │ │ └───┘ │ │ ┌───┐ │ │ ┌─────┼──┘ │ │ │LED│ │ Optical │ │ │ ┌──────┐ │ │ └───┘ │ Coupling│ ┌─┴─┐ │ ┌────┤SLEEVE│ Ground│ │ │ │ ───► │ │Rx │ │ │ └──────┘ │ │ GND ───────────┴────┼──────────┼──┤PT ├─┐ │ │ │ │ │ │ └─┬─┘ │ │ │ │ │ │ │ └───┼─┼──┘ │ │ RXD ◄───────────────┼──────────┼────────┼─┼──┐ │ │ │ │ │ │ │ │ │ ┌─┴─┐ │ ┌─┴─┐│ │ │ │ │Rx │ │ │LED││ │ │ │ │PT ├────────┼◄── └───┘│ │ │ │ └─┬─┘ │ │ │ │ │ │ │ │ ├──┘ │ │ │ VCC (+5V) ──[10kΩ]──┴──────────┼────────┼─────┘ │ │ │ │ │ └───────────────────────┘ │ ▼ 1N4148 │ │ ─── │ │ │ │ │ ▼ │ Use code with caution. Detailed Wiring & Circuit Logic 1. Transmit Path (PC to Radio)
The isolated circuit splits cleanly into two distinct sections separated by an isolation barrier: the and the Rig/Radio Side .
Check the 1N4148 diodes—they are often soldered incorrectly. icom ci v usb interface schematic top
When searching for , many users are trying to repair a non-working interface. Here’s how the top-level schematic helps diagnose faults:
Once the hardware is assembled, you must tell the radio and the software how to talk to each other: PC SIDE (USB POWERED) │ RADIO SIDE (RIG
Before plugging the interface into your expensive Icom rig, open a terminal program (like Putty or TeraTerm) on your PC, select the interface's COM port, and type some characters. If you do not have local echo enabled in the software but still see the characters you type on screen, your steering network is correctly looping the data back to the RX line.
Configure your USB-to-UART module’s voltage jumper to 5V . Do not leave it on 3.3V, as Icom TTL logic requires 5V thresholds. If you do not have local echo enabled
This classic transistor design is a fantastic learning project, but it's not the only path to CI-V control.
The bus is held high (5V) by a pull-up resistor when idle.