Isolated Rig Interface

This project is for a fully isolated rig interface unit for Echolink, FreeDV/Codec2 and other digital modes. It requires just a single USB cable from the PC to the interface and a single data cable from the interface to the data port which is available on most modern rigs. An optional second cable can be connected to the radio for CI-V/CAT control.


The interface includes the following features:

  • Completely surface mount technology based
  • Microcontroller controlled to allow for simpified operation
  • All connections to the radio are optically or galvanically isolated from the PC
  • Single USB interface to PC, which provides power, audio, control¬†and data interfaces
  • Single data connection to the radio, using the mini DIN data port
  • CI-V interface
  • Transmit time-out timer (software configurable time)
  • Hardware DTMF decoding
  • Headphone monitoring support for TX audio, RX audio or both
  • Optional LCD display for showing status
  • Echolink ASCII data support

Supported Modes

The interface should support any analog or digital mode that uses a sound card on the PC. This includes (but is certainly not limited to):

  • Echolink
  • PSK31
  • SSTV
  • Packet
  • APRS
  • FreeDV
  • WSPR

Please feel free to let me know of any other modes!


Version 3.0 of the interface is currently actively being developed. Schematics have been completed for:

  • USB Hub circuit
  • USB Audio circuit
  • USB Serial interface circuits
  • PTT / COS microcontroller interface
  • DTMF decoder circuit
  • Headphone switching circuit

Schematics still need to be completed for:

  • Front panel
  • CI-V interface

Block Diagram


See the history page for more details on the evolution of this project.