Icom Ci V Usb Interface Schematic Top
While commercial cables are widely available, building your own CI-V to USB interface is a highly rewarding, budget-friendly afternoon project. This comprehensive guide covers the top schematic designs, component selection, and step-by-step construction instructions. Understanding the Icom CI-V Protocol
Use legitimate FTDI drivers. Counterfeit chips (common on very cheap boards) often fail with official drivers.
High-end base stations where you want to daisy-chain multiple radios.
+---------------+ | USB Port | | (VCC, D+, D-) | +---------------+ | | v +---------------+ | FT232RL | | (QFN-20) | +---------------+ | VCC | 5V | | D+ | USB_D+ | | D- | USB_D- | | TX | TTL_TX | | RX | TTL_RX | | GND | GND | +---------------+ | | v +---------------+ | Voltage | | Regulator | | (5V or 3.3V) | +---------------+ | | v +---------------+ | R1 | 1kΩ | | R2 | 1kΩ | | C1 | 10uF | | C2 | 10uF | +---------------+ | | v +---------------+ | Radio | | Interface | | (CI-V) | +---------------+
The Icom CI-V bus is a where logic levels are roughly 0V (low) and 5V (high). To connect this to a computer via USB, follow these steps: icom ci v usb interface schematic top
Both the transceiver and the computer pull the line to ground (0V) to transmit data bits. This prevents damage if two devices attempt to transmit simultaneously.
When the phototransistor conducts, it pulls the CI-V bus down to ground, replicating the serial start/stop bits. 2. Receive Path (Radio to PC)
Below is a functional block diagram of the classic, proven “top-level” CI-V USB interface. Hundreds of online projects and commercial products (like the CT-17 or U5 Linker) follow this design.
Before examining the schematic, it’s critical to understand the CI-V electrical interface. Unlike RS-232, CI-V uses: While commercial cables are widely available, building your
[ PC USB-TTL Side ] [ Icom Radio Side ] TXD o----[ 470 Ohm ]----+ +----o CI-V Tip (Data) | | +-----+ +-----+ | LED | | Photo| +-----+ |Trans| | +-----+ GND o-------------------+ | +----o CI-V Sleeve (GND) RXD o-------------------+ +----o CI-V Tip (Data) | | +-----+ +-----+ |Photo| | LED | |Trans| +-----+ +-----+ | VCC o----[ 4.7k Pull-up ]+ +----[ 470 Ohm ]---o CI-V Tip (Data) Use code with caution. How it works: This circuit uses two optocouplers (e.g., or 4N35 ).
Creating a USB interface for the Icom CI-V, a protocol used by Icom radios for computer communication, involves designing a simple interface that converts the CI-V's serial signal to a USB signal that a computer can understand. The CI-V protocol uses a 9-pin D-sub connector with a specific pinout and typically operates at 9600 bps.
By building this interface, you shield your expensive transceiver from harmful electrical surges while securing a flawless, lag-free data pipeline for automated digital operation.
FTDI FT232RL or CH340K breakout board (outputs TTL-level TX/RX). Optocouplers: (2) 6N137 or 4N35 high-speed optocouplers. Diodes: (1) 1N4148 fast switching diode. Resistors: (2) 1kΩ, (1) 4.7kΩ, (1) 10kΩ. Counterfeit chips (common on very cheap boards) often
Connecting your Icom transceiver to a computer opens up a world of automated logging, digital modes, and rig control through software like Ham Radio Deluxe, WSJT-X, or fldigi. Icom radios use a proprietary communication protocol called CI-V (Computer Interface Five). While commercial cables are cheap, building your own CI-V to USB interface is an excellent afternoon project that helps you understand the hardware layer of your shack.
: Some designs use a hex buffer (e.g., 7417 or 4049) to isolate and combine signals for better stability.
Place a signal diode (1N4148) on the TX line (cathode towards the plug tip) to allow the RX line to read the bus without interference. Pro Tips for Builders G3VGR's USB CI-V and Winkey Interface - QSL.net
Once constructed, you need to configure the system to recognize the interface.
To merge the separate isolated TX and RX channels into a single line, a steering diode or a logic gate layout is used: