Icom Ci V Usb Interface Schematic Top Exclusive

Building a DIY Icom CI-V USB interface is a popular project for amateur radio operators looking to avoid the high cost of official cables like the Icom CT-17

. This guide covers the schematic and construction for a modern USB-to-CI-V interface using an FTDI chip. 1. Circuit Schematic & Operation The core of a modern USB CI-V interface is a USB-to-TTL UART converter

. Icom's CI-V bus uses a single-wire, bi-directional TTL (0–5V) signal where both transmit (TX) and receive (RX) data are combined onto one line. USB Controller FTDI FT232RL

is the most common choice as it handles all USB-to-serial conversion. The "Combining" Diode

: Since CI-V is a single-wire bus, you must connect the TXD and RXD pins of your USB chip together. A common method is connecting the RXD pin directly to the CI-V bus and using a 1N4148 diode

(anode to RXD/CI-V, cathode to TXD) to prevent the radio from being driven high by the TX pin when idle.

: Some designs include ferrite beads on the data and power lines to block stray RF noise. 2. Bill of Materials (BOM) You can find these parts at retailers like Specification FTDI FT232RL or CP2102 USB-to-UART Bridge Combines TX/RX for single-wire CI-V Pull-up resistor for the data line Capacitors 0.1 µF & 100 pF Noise bypassing and filtering 3.5mm Mono Plug Standard CI-V "Remote" jack connection Shielded Audio Cable Prevents RF interference 3. Construction Steps Prepare the USB Module

: If using a pre-made CP2102 or FT232RL breakout board, identify the Solder the Bridge

: Solder the 1N4148 diode and 10k resistor between the TXD and RXD pins as specified in your chosen schematic to create the single-wire bus. Wire the 3.5mm Jack Connect the of the 3.5mm mono plug to the combined TXD/RXD line. Connect the to the GND pin of the USB module. icom ci v usb interface schematic top

: Many builders use a small plastic project box or even a "Manhattan style" construction on a piece of unetched PCB board for a solid ground plane. www.ka6wke.net 4. Software Setup Explore USB with this USB to CI-V Interface - N5DUX

a USB to CI-V interface you can use. to control a radio with CI-V remote control. port capability and common radio frequency. USB- ICOM CI-V - K7MEM

Understanding the Icom CI-V USB Interface: A Top-Level Schematic Analysis

For decades, Icom has used its proprietary CI-V (Communication Interface-V) protocol to allow computers and accessories to control their transceivers (e.g., IC-7300, IC-9700, IC-705). While modern radios often include built-in USB ports, older or mid-tier models require an external "CI-V USB interface." This article dissects the top schematic of a typical universal Icom CI-V to USB converter.

Example configuration for common radios

Baud: often 19200 or 1200 bps depending on model — set adapter to match radio.
Logic: active-low open-collector style; use open-drain friendly interface.

1. Understanding the CI-V Bus: Why Opto-Isolation Matters

Before examining the schematic, it’s critical to understand the CI-V electrical interface. Unlike RS-232, CI-V uses:

Single-wire, half-duplex data (data in and out share one line).
TTL logic levels (0–5 V, active low).
Open collector bus – multiple devices (radio, antenna tuner, amplifier) share a common bus line.
No inherent galvanic isolation between the radio and connected device.

Without isolation, ground loops and RF interference from your transmitter can:

Freeze or corrupt computer control.
Damage the USB port or radio’s microcontroller.
Create hum, noise, or erratic behavior during transmit.

Thus, every robust CI-V USB interface schematic includes opto-isolation on both the receive and transmit paths.

Typical CI-V USB Interface – Top View Description

Board size: ~40×20 mm (e.g., similar to a CP2102 breakout)

Top side components (from left to right assuming USB connector on left edge): Building a DIY Icom CI-V USB interface is

| Region | Component | Label / Value | |--------|-----------|----------------| | Left edge | USB mini‑B or USB‑C | J1 (USB input) | | Next | USB‑to‑UART IC | CP2102 (QFN‑28) or CH340G (SOP‑16) | | Next | 3.3V regulator (if needed) | AMS1117‑3.3 (SOT‑223) | | Center‑right | Dual transistor / inverter | 2N7002 (x2) or BC547 (x2) or IC like 74HC05 (open‑drain) | | Right edge | 3‑pin header | J2: Tip (DATA), Ring (GND), Sleeve (optional +5V) → to 3.5mm TRS jack (Icom CI‑V plug) |

Top copper traces (conceptual):

USB D+ / D‑ go from J1 to IC pins (CP2102 pins 4 & 5 or CH340 pins 6 & 7).
UART TX (from IC) goes to base/gate of Q1 (inverter stage).
Collector/drain of Q1 pulls the CI‑V data line low (open collector).
UART RX (to IC) goes from CI‑V data line via a protection resistor (1kΩ) and optionally a second inverter stage for correct polarity.
CI‑V data line has a 4.7kΩ pull‑up to +5V (or to radio’s Vcc via the TRS cable).
Ground plane on bottom side (not visible from top).

Notes:

Ensure that the cable used for the CI-V connection is not too long, as this can affect signal integrity.
Be careful with the PTT and other signals not used by CI-V; they might be used by other software or functions.
The success of the project depends on the correct assembly, configuration, and communication software setup.

This guide provides a basic understanding. For detailed electronics expertise and specific component values (like which resistors and capacitors are needed), refer to FTDI documentation and Icom's CI-V protocol specifications. Always follow best practices for electronics assembly and safety.

Building a DIY Icom CI-V (Computer Interface V) USB interface is a popular project for enabling rig control on transceivers that don't have a native USB port. The interface functions by converting standard computer logic levels into a single-wire, half-duplex bus that communicates with the radio at TTL (0-5V) levels Interface Overview The CI-V protocol uses a 3.5mm mono phone jack

(standard headphone jack size). Data is sent and received over the same wire, making it a half-duplex system. Core Schematic Components A modern USB-to-CI-V interface typically centers around a USB-to-UART bridge chip , such as the FTDI FT232RL

Connects to the PC, usually via a standard USB-A or Micro-USB connector. Conversion Logic: TXD (Transmit) RXD (Receive)

pins of the UART chip must be tied together to interface with the single-wire CI-V bus.

(e.g., 1N4148) is often placed between the TXD line and the CI-V bus to prevent the chip from "fighting" incoming signals when not transmitting. pull-up resistor Understanding the Icom CI-V USB Interface: A Top-Level

(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:

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

Building your own Icom CI-V (Communications Interface 5) USB interface is a popular DIY project for amateur radio operators. It allows you to control transceivers—from older models like the IC-735 to modern rigs—via a computer using a single 3.5mm mono cable. Understanding the CI-V Bus

The CI-V protocol is a bi-directional, single-wire TTL system. Unlike standard RS-232 serial communication which uses separate Transmit (TX) and Receive (RX) lines, CI-V combines them into one "DATA" line. Idle State: The line is held high (+5V TTL). Collision Detection: If the line is low, the bus is "busy".

Daisy Chaining: Multiple Icom devices can be connected in parallel; each is identified by a unique hex address. Core Schematic: USB-to-TTL (CI-V)

To build a modern USB version, you need a USB-to-TTL serial converter (often based on the FTDI FT232RL or CP2102 chips). The "Two-Diode" or "Shorted" Method

The simplest way to interface a standard USB-to-TTL module (which has separate TX and RX pins) with the single-wire CI-V bus is to bridge the signals.

TX to DATA: Connect the TXD pin of your USB module to the Tip of a 3.5mm mono jack through a small signal diode (e.g., 1N4148) with the cathode facing the USB module. This prevents the TX pin from holding the bus high when it should be idle. RX to DATA: Connect the RXD pin directly to the same Tip. Ground: Connect the GND pin to the Sleeve of the mono jack. Buffered Open-Collector Schematic

For a more robust "top-tier" design that prevents data collisions and protects your radio, use an Open-Collector Buffer like the 7417 or 7407. Simple Icom CI-V Interface - QSL.net