Open your computer's device manager to verify which COM port number has been assigned to the interface (e.g., COM3).
Connect all radio-side grounds together: , Pin 5 of IC 2, and Pin 5 of IC 3. Configuration and Software Setup
, or chips). These modules provide separate TX (Transmit) and RX (Receive) pins, which must be combined into the single-wire CI-V bus. Simple Diode/Resistor Circuit
The chip's TXD (Transmit Data) and RXD (Receive Data) pins are routed to the host-side pins of the optocouplers. 2. The Isolation Stage (Optocouplers) icom ci v usb interface schematic top
| | Pin / Conductor | Signal | Description | | ---------------------- | ------------------- | ------------------ | ------------------------------------------------- | | 3.5mm Mono Jack | Tip | CI-V Data (Single-wire bus) | Bi-directional data line at 5V TTL levels | | 3.5mm Mono Jack | Sleeve | Ground (GND) | Common ground reference |
If you are building one from scratch today, is highly recommended.
Searching for the is the first step toward an immensely rewarding homebrew project. A top‑level schematic gives you the big picture, but it is the small details —the open‑collector driver, the pull‑up resistor, the correct baud rate, and the proper CI‑V address—that make the difference between a frustrating debugging session and a smooth, reliable computer‑radio interface. Open your computer's device manager to verify which
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.
Connecting this to a USB port requires converting asynchronous USB data (TX/RX) into a single-wire TTL stream. 2. Top Icom CI-V USB Interface Schematic (DIY) The most robust DIY schematic uses an FTDI FT232RL Go to product viewer dialog for this item. or Go to product viewer dialog for this item.
Connect all PC-side grounds together: FT232RL GND, Pin 5 of IC 2, and Pin 5 of IC 3. Step B: Wiring the Radio Side (Isolated Domain) These modules provide separate TX (Transmit) and RX
The Icom CI-V system is a serial communication protocol used to control Icom radios. It uses a simple two-wire interface (Data and Ground) that operates at TTL logic levels (5V).
However, a computer's modern USB port speaks neither TTL voltages nor the CI-V bus logic. Its signals are digital, and the USB hardware expects to talk to something like a virtual serial port. For CI-V to work, we need an interface that does three things:
The simplest approach to building a USB interface is to use a as the foundation. These inexpensive cables (often based on the FTDI FT232R, Prolific PL2303, or Silicon Labs CP2102 chip) convert your computer's USB port into a TTL-level serial port. From there, adding a few transistors completes the CI-V interface. The following schematics are based on classic, proven designs from the amateur radio community.
For a permanent shack installation, isolating the radio from the PC is paramount. This schematic uses two high-speed optocouplers (such as the 6N137 or 4N35) to bridge the gap safely.
Open your computer's device manager to verify which COM port number has been assigned to the interface (e.g., COM3).
Connect all radio-side grounds together: , Pin 5 of IC 2, and Pin 5 of IC 3. Configuration and Software Setup
, or chips). These modules provide separate TX (Transmit) and RX (Receive) pins, which must be combined into the single-wire CI-V bus. Simple Diode/Resistor Circuit
The chip's TXD (Transmit Data) and RXD (Receive Data) pins are routed to the host-side pins of the optocouplers. 2. The Isolation Stage (Optocouplers)
| | Pin / Conductor | Signal | Description | | ---------------------- | ------------------- | ------------------ | ------------------------------------------------- | | 3.5mm Mono Jack | Tip | CI-V Data (Single-wire bus) | Bi-directional data line at 5V TTL levels | | 3.5mm Mono Jack | Sleeve | Ground (GND) | Common ground reference |
If you are building one from scratch today, is highly recommended.
Searching for the is the first step toward an immensely rewarding homebrew project. A top‑level schematic gives you the big picture, but it is the small details —the open‑collector driver, the pull‑up resistor, the correct baud rate, and the proper CI‑V address—that make the difference between a frustrating debugging session and a smooth, reliable computer‑radio interface.
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.
Connecting this to a USB port requires converting asynchronous USB data (TX/RX) into a single-wire TTL stream. 2. Top Icom CI-V USB Interface Schematic (DIY) The most robust DIY schematic uses an FTDI FT232RL Go to product viewer dialog for this item. or Go to product viewer dialog for this item.
Connect all PC-side grounds together: FT232RL GND, Pin 5 of IC 2, and Pin 5 of IC 3. Step B: Wiring the Radio Side (Isolated Domain)
The Icom CI-V system is a serial communication protocol used to control Icom radios. It uses a simple two-wire interface (Data and Ground) that operates at TTL logic levels (5V).
However, a computer's modern USB port speaks neither TTL voltages nor the CI-V bus logic. Its signals are digital, and the USB hardware expects to talk to something like a virtual serial port. For CI-V to work, we need an interface that does three things:
The simplest approach to building a USB interface is to use a as the foundation. These inexpensive cables (often based on the FTDI FT232R, Prolific PL2303, or Silicon Labs CP2102 chip) convert your computer's USB port into a TTL-level serial port. From there, adding a few transistors completes the CI-V interface. The following schematics are based on classic, proven designs from the amateur radio community.
For a permanent shack installation, isolating the radio from the PC is paramount. This schematic uses two high-speed optocouplers (such as the 6N137 or 4N35) to bridge the gap safely.