Icom Ci V Usb Interface Schematic Top !!install!! Jun 2026

Notes:

Draw a physical clearance gap (at least 2mm to 5mm wide) across the board. No copper traces, ground planes, or power planes should cross this line. The only components spanning this gap must be the physical bodies of the optocouplers.

The radio side utilizes a standard 3.5mm mono phone jack. The tip carries the bi-directional data, while the sleeve provides the ground reference. 2. Core Components Selection

Before diving into the hardware components, it is critical to understand how the CI-V system transmits data. icom ci v usb interface schematic top

: Use shielded audio cable for the connection between the interface and the radio's "Remote" jack to minimize RF interference.

This was the standard design in the 1990s and 2000s. It converts USB to RS-232 voltages (+/- 12V), and then converts that back down to TTL for the radio.

[ PC USB Port ] │ ┌──────┴────────────────────────┐ │ USB to UART Bridge │ (FT232RL or CH340G) │ (Powered by PC USB +5V) │ └────┬────────────────────▲─────┘ │ TX │ RX ┌────▼────┐ ┌────┴────┐ │ Opto │ │ Opto │ │ Coupler │ │ Coupler │ <--- ISOLATION BARRIER │ (TX) │ │ (RX) │ └────┬────┘ └────▲────┘ │ │ ┌────▼────────────────────┴─────┐ │ Bi-Directional Bus Combiner │ │ (Powered by Radio CI-V Port) │ └───────────────┬───────────────┘ │ [ Icom CI-V Jack ] Detailed Circuit Component Breakdown 1. USB-to-UART Bridge (Host Side) Notes: Draw a physical clearance gap (at least

The schematic for this interface is straightforward. You are essentially building the "bus combining" circuit described in the earlier two-transistor design.

The bus operates at standard 5V TTL logic levels.

The anode of the input LED connects to the USB +5V through a 330-ohm current-limiting resistor. The cathode connects directly to the FT232RL TXD pin. When TXD goes low, the LED illuminates. The radio side utilizes a standard 3

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 CI-V protocol uses a bi-directional, single-wire system where the TX and RX lines from the converter are tied together. Level Conversion

. These chips convert USB data into standard asynchronous serial signals.

One builder reported that their simple two‑transistor interface worked perfectly on a native COM port but failed when used through a USB‑to‑serial converter; the problem was insufficient power available on the modem control lines. The solution was to either reconfigure the interface for external power or use a different USB‑to‑serial adapter.