Icom Ci V Usb Interface Schematic Top _top_ May 2026

Understanding the ICOM CI-V USB Interface Schematic: A Comprehensive Guide

Radio Side (9-pin D-sub):

Pin 1: PTT (not used in CI-V)
Pin 2: Tx (CI-V): From FTDI RXD
Pin 3: Rx (CI-V): To FTDI TXD (Note: For simple cable designs, often ignore or terminate)
Pin 4: GND: Common ground
Pin 5: SQL (not used in CI-V)
Pin 6: RTS (CI-V): To FTDI CTS
Pin 7: CTS (CI-V): To FTDI RTS
Pin 8: Data (not used)
Pin 9: NC (not connected)

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: icom ci v usb interface schematic top

This chip has "Open Collector" outputs built-in.
You would feed the TTL TX signal into the Inverter input, and the Inverter output goes to the radio.
This provides a very clean, robust drive that handles multiple radios on one line better than a single transistor.

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 Understanding the ICOM CI-V USB Interface Schematic: A

[USB Port] → [USB-to-UART bridge] → [Opto-isolation stage (TX direction)] → [Buffer/Driver] → [CI-V connector (3.5mm TRS)]
                                                    ↑
[CI-V connector] → [Signal conditioning] → [Opto-isolation stage (RX direction)] → [UART RX]

The CI-V bus is a single-wire, bi-directional serial communication system that operates at TTL voltage levels (0V to 5V). Pin 1: PTT (not used in CI-V) Pin

USB to RS-232: Use a USB-to-Serial adapter (like a Keyspan or generic Prolific/FTDI cable) to get a standard DB9 RS-232 port.
Level Conversion (The Interface Box):