Icom Ci V Usb Interface Schematic Top ((top))

Plug the USB interface into your computer. Windows, Mac, or Linux should automatically download the drivers for your chip (FTDI or CH340). Check your device manager to see which COM Port has been assigned.

Note: This configuration causes the computer to "hear" its own echoes. Most software, like Omni-Rig, Ham Radio Deluxe, or fldigi, handles this automatically.

Connect the anode (non-striped side) of the diode to the board's pin.

The Icom CT-17 is the gold-standard interface. It served a single purpose: to act as a level converter between an RS-232 COM port and the CI-V bus, providing the necessary TTL signaling and bus driving capability. The CT-17 contains a simple circuit that:

Icom’s official interface (e.g., or internal USB in IC‑7300/9700) is proprietary. You can: icom ci v usb interface schematic top

is used to handle the voltage translation between +/-12V (RS-232) and 0-5V (TTL).

Do you prefer using or an off-the-shelf breakout board ?

| 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) |

[USB] ---> [UART Chip] ---> [Signal Splitter/Diode] ---> [3.5mm CI-V Jack] (FTDI/CP2102) (1N4148 Diodes) Use code with caution. USB Type-A or Mini/Micro B connector. Plug the USB interface into your computer

CI‑V uses (one‑wire bidirectional data). The USB side (UART) is standard TTL (non‑inverted). So you need:

Both the transceiver and the computer pull the line to ground (0V) to transmit data bits. This prevents damage if two devices attempt to transmit simultaneously.

Set the (default 0x5E for IC-7000, 0x76 for IC-7300, etc.) in your software (e.g., WSJT-X, FLRig, HRD).

Unlike standard RS-232 or TTL serial which uses separate Transmit (TX) and Receive (RX) lines, CI-V combines TX and RX onto a single bi-directional line. Note: This configuration causes the computer to "hear"

In your software (Ham Radio Deluxe, Fldigi, WSJT-X), select the assigned COM port. Baud Rate: Set to 1920019200 (default for most modern Icom) or "Auto".

Follow these step-by-step pin connections to assemble the interface on a prototyping board or custom PCB. Step A: Wiring the PC Side (USB Domain)

: Because the CI-V bus is a single wire, the separate TX and RX lines from the USB chip must be merged. The "Diode Trick"

These circuits can be "port-powered" using the RTS or DTR lines, or powered externally with a 5V regulator like the Critical Specs for Your Build Signaling: 1-wire bidirectional TTL ( ); data line is when idle. Baud Rate: