Notes:
When searching for "icom ci v usb interface schematic top", many users are trying to repair a non-working interface. Here’s how the top-level schematic helps diagnose faults:
| Symptom | Likely area (top-level block) | |-----------------------------|----------------------------------------------| | No control, but radio responds to CI-V commands from another device | USB-to-UART bridge (check drivers, TX/RX LEDs) | | Erratic control, especially on transmit | Lack of opto-isolation or ground loop | | Computer sees COM port, but no PTT or frequency readout | TX opto (IC2) or buffer transistor dead | | Stuck data (bus always low) | Open collector transistor shorted, or missing pull-up on CI-V line | | Interface works only at low baud rates | Optocoupler too slow (replace 4N35 with 6N137) |
If you want, I can:
(Invoking related search suggestions...)
An Icom CI-V USB interface acts as a bridge between a modern computer's USB port and the TTL-level serial bus used by Icom transceivers for remote control. While commercial versions can be expensive, a DIY interface is highly effective and can be built using standard USB-to-UART components. Core Interface Features
Single-Wire Communication: The CI-V (Computer Interface 5) protocol uses a bi-directional, single-wire TTL signaling system where a single "DATA" line is held high until a device pulls it low to initiate communication. USB-to-Serial Conversion
: Modern schematics center around a bridge IC, most commonly the FTDI FT232RL Go to product viewer dialog for this item. or the Silicon Labs CP2102 Go to product viewer dialog for this item.
. These chips convert USB data into standard asynchronous serial signals.
Logic Level Shifting: The interface converts standard computer signals to the 5V (TTL) levels required by the radio.
Collison Management: It utilizes a CSMA/CD system to manage traffic on the shared bus, ensuring over 90% bus efficiency. Schematic Topography and Key Components
Building a USB CI-V interface generally involves three main functional blocks: G3VGR's USB CI-V and Winkey Interface - QSL.net
The workbench was a graveyard of half-finished projects until the ICOM CI-V interface arrived. For a radio op, it wasn’t just a cable; it was the bridge between a legacy rig and modern digital wizardry.
I remember staring at the top-down schematic, a clean blueprint of logic in a world of messy RF. At the heart sat the FT232R chip, the silent translator converting USB’s frantic data into the steady, open-collector pulses the ICOM radio understood. To its left, a single 1N4148 diode stood guard—a simple gatekeeper ensuring the TX and RX lines played nice on the single-wire bus without talking over each other.
The "Top" view of the PCB layout was a work of art. Traces curved like copper rivers, snaking around tiny 0.1µF capacitors that filtered out the hum of the Shack’s power supply. I remember the smell of fresh solder as I bridged the pads, following the diagram's path from the USB-B port straight to the 3.5mm mono jack.
When the last joint cooled, I plugged it in. The computer chimed, the rig’s frequency flickered to life on the screen, and just like that, the schematic wasn’t a drawing anymore—it was a conversation.
The Icom Communications Interface V (CI-V) is a proprietary serial communication bus used to remotely control Icom amateur radio equipment. While Icom sells the CT-17 level converter, you can easily build a high-performance USB CI-V interface using inexpensive USB-to-TTL modules. CI-V Technical Overview
The CI-V bus is an open-collector, bi-directional, single-wire system operating at TTL (5V) logic levels.
Idle State: The DATA line is held HIGH (+5V) by a pull-up resistor.
Active State: Devices communicate by pulling the line LOW (0V).
Connector: A standard 3.5mm mono jack. The tip carries the DATA signal, and the sleeve is GND. The "Top" Schematic: USB-to-TTL Method
The most efficient DIY design uses a common USB-to-Serial board (like those based on FTDI FT232RL , CP2102
, or CH340 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
This is the most popular "top" schematic for its simplicity and reliability.
Join TX and RX: Connect the RX pin of the USB module directly to the CI-V Tip. Add a Diode: Connect the anode of a small signal diode (e.g., 1N4148
) to the CI-V Tip and the cathode to the TX pin of the USB module.
Purpose: This allows the TX pin to pull the bus low but prevents it from forcing the bus high, maintaining the open-collector requirement.
Pull-up Resistor: Connect a 4.7kΩ to 10kΩ resistor between the CI-V Tip and the 5V VCC pin on the USB module to ensure the bus idles high. Key Components List USB-to-TTL Module: FTDI FT232RL modules are highly recommended for driver stability. Diode: or similar high-speed switching diode. Resistor: 4.7kΩ (standard for CI-V). Plug: 3.5mm (1/8") Mono Phone Plug. Cable: Shielded audio cable to prevent RF interference. Software Setup
Once hardware is ready, you will need software to communicate with the rig. Popular choices include: Icom IC7300 A to Z #27 CI-V Settings
CI-V (Computer Interface V) system is a standard protocol used by Icom transceivers for remote control. Because it uses an open-collector, half-duplex TTL-level signal, it requires an interface to convert these signals to levels a computer can understand, such as USB. Core Schematic Components A modern USB-to-CI-V interface typically revolves around a USB-to-Serial UART chip (like the FTDI FT232RL or Silabs CP2102). USB Bridge Chip : Converts USB data into TTL (0–5V) serial signals. Diode & Resistor Combination
: Since CI-V combines Transmit (TX) and Receive (RX) onto a single wire, a small circuit is needed to bridge the TX and RX pins of the UART chip. 3.5mm Mono Jack
: The standard physical connection for the radio end of the cable. Top Schematics & Design Options CI-V interface - Tučňák Wiki Tucnak - Nagano.cz Easy to make CI-V cable www.maniaradio.it Simple Icom CI-V Interface Yet Another ICOM CI-V Interface circuit | Next Electronics Next.gr Electronics Icom CI-V Interfaces and CT-17 Replacement – VK4AMG
ICOM CI-V to RS232 interface diagram (using transistors, very small) ICOM CI-V Interface Seed Solutions CI-V interface - Tučňák Wiki Tucnak - Nagano.cz icom ci-v interface KA1MDA HOME PAGE
The Icom CI-V (Computer Interface 5) USB interface schematic typically centers around a USB-to-Serial converter IC, such as the FTDI FT232RL Go to product viewer dialog for this item. Go to product viewer dialog for this item.
, which bridges the computer's USB port to the radio's single-wire TTL bus. Core Schematic Components USB-to-Serial Converter: Modern designs often use the or Go to product viewer dialog for this item.
. These chips handle all USB protocol tasks and provide TTL-level Transmit (TX) and Receive (RX) signals.
Single-Wire Bus Logic: 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
: Because the radio operates on a shared "open collector" bus, the schematic usually includes a diode (like a ) or a buffer (like a
) to prevent the TX line from interfering with the RX line when the radio is sending data.
Pull-up Resistor: A resistor (often around 4.7kΩ to 10kΩ) pulls the DATA line high when idle. Isolation & Protection:
Ferrite Beads and Capacitors: Used on the USB power line and radio data lines to block RF interference and noise. Isolation Transformers
: Some advanced homebrew designs include isolation transformers to prevent ground loops between the computer and the radio.
Push-To-Talk (PTT): Many schematics add a sub-circuit using the RTS (Ready to Send) or DTR (Data Terminal Ready) line from the serial converter to trigger a transistor (e.g., ) for PTT or CW keying. Connection Layout
USB Side: Connects to the PC; the converter chip is powered by the USB 5V line. Radio Side: Uses a 3.5mm mono phone plug. Tip: Data signal (bi-directional TTL). Sleeve: Ground reference. Icom IC7300 A to Z #27 CI-V Settings
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).
Modern computers no longer have serial ports (RS-232), and CI-V is not directly compatible with USB. Therefore, an interface is required to bridge the gap. The schematic design depends entirely on which USB chip you choose to use.
Here are the three most common schematic topologies, ranging from the easiest to build to the most traditional.
USB Type-B USB-to-UART Level Shifter CI-V (to radio)
───────── ────────────── ───────────── ─────────────
VBUS ────────────────► VCC (5V)
│
D+ ──────────────────► USBD+ (FTDI/CP2102)
D- ──────────────────► USBD-
│
GND ──────────────────► GND
│
TXD ──────────┬──────────► Level Shifter (e.g., 2N7000 or MAX232)
RXD ◄─────────┼──────────►
│ │
└─── 10k pull-up to 5V ──┐
│
┌────┴────┐
│ 2N7000 │
│ MOSFET │
└────┬────┘
│
CI-V Data ────────────┘ (Open collector)
(3.5mm jack tip)
GND ─────────────────── (sleeve)
The term "top" could also refer to the top side of the PCB or top layer routing in an EDA tool like KiCad or Eagle. For a successful layout: