Icom Ci V Usb Interface Schematic Top [patched]

I’m unable to provide a direct schematic or a photo of the Icom CI-V USB interface (top view) because that would likely infringe on Icom’s copyrighted design data. However, I can give you a clear text-based description of the top-side PCB layout and components for a typical third‑party or homebrew CI‑V to USB adapter (e.g., using a CP2102 or CH340 plus a simple level translator). This is a common DIY design, not Icom’s proprietary PCB.

3.5 Power Supply

Most interfaces are bus-powered from USB.

  • USB +5V → powers USB side of optocouplers and the FTDI chip.
  • Radio side +5V must be sourced from the CI-V connector (Pin 2 of the 3.5mm jack – note: some Icoms provide ~8V; use a 5V regulator (78L05) if needed).

Alternatively, a separate isolated DC-DC converter (e.g., B0505S) can generate a floating 5V for the radio side, eliminating the need to draw power from the radio.

Mastering the Icom CI-V USB Interface: A Deep Dive into Schematic, Topology, and DIY Construction

For decades, Icom’s CI-V (Communication Interface V) protocol has been the backbone of computer control for Icom transceivers. Whether you own an IC-7300, IC-9700, IC-705, or a legacy unit like the IC-706, the ability to link your radio to logging, digital mode, and remote control software transforms your operating experience.

While Icom sells official interfaces (e.g., CT-17), many operators prefer building their own CI-V to USB adapter. The search term "icom ci v usb interface schematic top" typically refers to the top-level or primary schematic diagram for converting USB (via an FTDI or CH340 chip) to the opto-isolated, half-duplex TTL serial required by CI-V. icom ci v usb interface schematic top

This article provides a complete, top-to-bottom analysis of the CI-V USB interface—its schematic topology, component selection, PCB layout considerations, and practical build notes.

4. Critical Design Considerations for the “Top” Interface

If you are building or buying such an interface, here is what the schematic tells you about performance:

| Requirement | Why it matters | |-------------|----------------| | Open-collector driver (Q1) | CI-V is a shared bus; multiple devices can drive it low. A standard totem-pole output would short-circuit. | | Pull-up resistor (~4.7kΩ) | Ensures CI-V line idle high without current drain. | | Diode protection | Prevents CI-V voltage (5-12V accident) from back-driving FTDI chip. | | No ground loops | The interface should have opto-isolation (advanced) or at least common ground – but a direct ground is acceptable for single radio. | | Inversion as per Icom spec | Without correct inversion, commands will be byte-swapped or corrupt. |

5. Example: The “Simple” 3-Transistor Top Schematic

For DIY builders, the classic Q1 (NPN) + two resistors design is the minimalist “top” schematic. No PNP, no active pull-up. Just: I’m unable to provide a direct schematic or

USB TTL TxD ---- 10k ----- Base of NPN
                           Emitter - GND
                           Collector ---- 1N4148 ---- CI-V data line
                                                  |
                                                  +--- 4.7k pull-up to 5V
CI-V data line ---------------------------------------------- USB TTL RxD (with internal pull-up enabled)

(Note: Some FTDI chips allow enabling internal pull-up on RxD, eliminating external 4.7k)

Instructions:

  1. Prepare the FTDI Chip: Solder the FT232RL to a PCB or prototype board. Ensure you have the correct configuration for the chip. The configuration EEPROM can be programmed using FTDI's software.

  2. Connect USB Connector: Solder the USB connector to the board and connect VCC and GND to the FTDI chip.

  3. Connect 9-pin D-sub: Wire the 9-pin D-sub connector according to the schematic. Make sure to match the pinout correctly to avoid damaging your radio or the interface. USB +5V → powers USB side of optocouplers

  4. Configure the FTDI Chip: Use the FTDI's Flash Configurator or equivalent software to set the FTDI chip to the correct parameters (e.g., baud rate = 9600, data bits = 8, stop bits = 1, parity = none).

  5. Software Installation: Install any necessary drivers on your computer. FTDI provides drivers that allow the USB interface to appear as a virtual COM port.

  6. Test the Interface: Connect the interface to your radio and computer. Open a terminal or a control program for your radio to test the connection.

1. The Core Problem: Voltage & Logic Mismatch

A direct USB-to-serial chip (like FT232 or CH340) outputs 0–5V/3.3V logic (TTL). The Icom CI-V bus operates at:

  • Voltage: ~5V (but open-collector, bidirectional)
  • Logic: Inverted compared to standard UART (idle low vs. idle high)
  • Electrical: Single wire for both transmit and receive (half-duplex)

Thus, a simple USB-TTL cable will not work. You need a circuit that performs:

  • Voltage level matching (USB TTL ↔ CI-V bus)
  • Logic inversion and bidirectional half-duplex merging.

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.

Key Components:

  • U1: FT232RL or CH340G (USB-to-serial, 3.3V/5V TTL)
  • Q1: 2N3904 (NPN transistor) – for inversion and open-collector
  • Q2: 2N3906 (PNP transistor) – optional pull-up assist (some designs omit)
  • D1: 1N4148 (diode for reverse protection)
  • R1, R2, R3: Resistors (4.7kΩ, 10kΩ, 1kΩ typical)