Connect the anode of the diode to the RXD pin using a small piece of hookup wire.
A very low-cost chip frequently found on Arduino boards, though driver installation can sometimes require manual intervention on older operating systems. TX/RX Combining Network icom ci v usb interface schematic top
Because the USB bridge separates data into distinct TXD and RXD pins, you must combine them into the single-wire CI-V line without causing data collisions or looping your own transmissions back into the computer blindly (though the CI-V protocol natively expects to "echo" transmissions back to the controller). Optoisolation (Highly Recommended) Connect the anode of the diode to the
Set both DTR and RTS to "Low" or "None". Optoisolation (Highly Recommended) Set both DTR and RTS
For decades, Icom has used its proprietary 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.
This classic transistor design is a fantastic learning project, but it's not the only path to CI-V control.
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)