RimuCAT Guide

RimuCAT bridges the FlexRadio network protocol to a standard CAT interface, letting logging programs, digital-mode software, and automation tools control your radio from Linux.

Connecting RimuCAT CAT Port

RimuCAT · TCP · Virtual Serial Port · FlexRadio 6000 · 8000 · Aurora

RimuCAT interface with an active CAT connection

What RimuCAT Does

RimuCAT is the CAT control component of the RimuSDR suite. It translates the FlexRadio network protocol into a standard CAT interface that external software can connect to over TCP or through a virtual serial port.

TCP Connections

The recommended connection method for modern software such as WSJT-X and N1MM+.

Create a TCP listener on any port you choose
Configure external software as FlexRadio 6xxx rig type
Point it to localhost and the port you selected
Multiple TCP connections supported simultaneously

Virtual Serial Ports

For software that only supports serial port CAT, such as Fldigi and older logging programs.

Creates a virtual port that appears under /dev/
Behaves like a real serial device
Works with any software that supports serial CAT control
Multiple virtual ports can be created simultaneously

What CAT Provides

Full bidirectional control of frequency, mode, and transmit state.

Read and set VFO frequency
Read and set operating mode
PTT keying for transmit control
Radio state updates pushed to connected software
FlexRadio 6xxx command set for TCP connections

Connecting RimuCAT to Your Radio

RimuCAT must be connected to the same FlexRadio station as RimuSDR before any CAT connections will work. Follow these steps to get RimuCAT running.

Start RimuSDR first

RimuSDR must be connected to the radio before RimuCAT is started. RimuCAT relies on the same station connection that RimuSDR establishes.

Open RimuCAT

Launch RimuCAT from your applications menu or from the RimuSDR interface. RimuCAT will appear in its own window alongside RimuSDR.

Connect to the station

In RimuCAT, select the same station that RimuSDR is connected to and click Connect. RimuCAT will show a connected status once it has established its own link to the radio.

Idle until a connection is created

After connecting RimuCAT to the station, it will sit idle until you create at least one TCP or virtual serial port CAT connection. This is expected behavior — RimuCAT does not expose any CAT endpoint until you configure one.

RimuCAT interface showing connection status and CAT connection list — RimuCAT after connecting to a station and creating a TCP CAT connection. The connection list shows the type, port, and status of each configured endpoint.

CAT Port

The CAT port provides bidirectional radio control — frequency, mode, and PTT — to external software. Multiple simultaneous CAT connections are supported; use a different port number for each application and they can all control the radio at the same time.

TCP Connections

TCP is the recommended method for most modern ham radio software. It requires no virtual device setup — just a port number and the correct rig type in your external application.

Create a TCP connection

In RimuCAT, click Add TCP Connection and enter a port number. Port 60000 is a common choice, but any unused port above 1024 will work. Click OK to start the listener.

Configure your external software

In your logging or digital-mode application, set the rig type to FlexRadio 6xxx and point it to localhost (or 127.0.0.1) on the port you chose. Do not use a serial port setting — select the network or TCP option in your software.

Test the connection

Use the Test CAT function in your external software (for example, in WSJT-X under Settings › Radio). A successful test confirms that RimuCAT is receiving commands and the rig type and port are correct.

TCP connection settings reference

Rig typeFlexRadio 6xxx (in WSJT-X, N1MM+, and most modern loggers)
Hostlocalhost or 127.0.0.1 (when RimuCAT and the application are on the same machine)
PortThe port number you set in RimuCAT — for example, 60000
Poll rateUse the software default; RimuCAT also pushes state changes to connected clients without polling

Virtual Serial Connections

RimuCAT can create software virtual serial ports that appear under /dev/ exactly like a real serial device, for applications that only support serial port CAT.

Create a virtual serial port

In RimuCAT, click Add Serial Connection and select the virtual port option. RimuCAT will create the port and display the device path — for example, /dev/ttyCAT0. Note the path for use in your application.

Configure your software

Open the serial port settings in your application and enter the device path shown in RimuCAT. The baud rate setting is ignored since there is no physical hardware involved.

Port availability

The virtual port exists only while RimuCAT is running and connected. If RimuCAT is closed or disconnected, the port disappears and applications holding it open will need to reconnect.

Serial Connections

RimuCAT can bridge CAT control to a real hardware serial port, allowing legacy hardware or software that requires a physical serial device to communicate with the radio.

Create a hardware serial connection

In RimuCAT, click Add Serial Connection and select the hardware serial option. Choose the physical port device from the list — for example, /dev/ttyUSB0 for a USB-to-serial adapter.

Baud rate

Set the baud rate to match what your connected hardware or software expects. Unlike virtual serial ports, the baud rate is applied to the physical device.

Use case

Hardware serial connections are useful for legacy logging hardware, external devices, or any situation where a physical RS-232 or USB-serial interface is required.

dialout group

On Linux, access to serial port devices requires membership in the dialout group. If the port does not appear or RimuCAT cannot open it, add your user account to the group with sudo usermod -aG dialout $USER and then log out and back in for the change to take effect.

PTT Port

The PTT port provides a dedicated transmit keying interface separate from CAT control. Use a PTT port when your application needs to key the radio for transmit independently of CAT commands.

TCP Connections

Create a TCP PTT listener for applications that support network-based PTT control.

Create a TCP PTT connection

In RimuCAT, click Add PTT Connection, select TCP, and enter a port number. The listener will start immediately and accept PTT commands from the connected application.

Configure your software

In your application's PTT settings, select the TCP option and point it to localhost and the port you configured in RimuCAT.

Virtual Serial Connections

A virtual serial port PTT connection is useful for applications that key transmit using the RTS or DTR line of a serial port.

Create a virtual serial PTT port

In RimuCAT, click Add PTT Connection and select virtual serial. RimuCAT will create a port under /dev/. Configure your application to use that port for PTT keying via RTS or DTR.

RTS vs DTR

Check your application's documentation to determine whether it keys PTT using RTS or DTR and configure RimuCAT to match.

Serial Connections

For hardware that keys PTT via a physical serial port — such as a USB-to-serial adapter wired to a keying circuit — RimuCAT can monitor the RTS or DTR line and translate it into radio transmit control.

Create a hardware serial PTT connection

In RimuCAT, click Add PTT Connection, select hardware serial, and choose the physical port device. RimuCAT will monitor the selected line (RTS or DTR) and key the radio when it is asserted.

Use case

This is useful for footswitch interfaces, external keying circuits, or any hardware that drives a serial port line to control transmit.

dialout group

On Linux, access to serial port devices requires membership in the dialout group. If RimuCAT cannot open the port, add your user account to the group with sudo usermod -aG dialout $USER and then log out and back in for the change to take effect.

Related Guides

Step-by-step integration guides for connecting digital-mode and logging applications to RimuSDR.

RimuSDR User Guide

Full coverage of the RimuSDR suite including radio connection, panadapter controls, DAX audio configuration, CAT setup, and the CWX keyer.

WSJT-X Setup Guide

Configure WSJT-X for FT8, FT4, and related weak-signal digital modes using RimuDAX for audio and RimuCAT TCP for CAT control.

Fldigi Setup Guide

Configure Fldigi for HF digital modes using RimuDAX audio and a RimuCAT virtual serial port for CAT control.

Installation Guide

Download and install RimuSDR, RimuDAX, and RimuCAT on Debian, Ubuntu, Raspberry Pi, or via AppImage, and activate your license.