FlexControl Tuning Knob

FlexControl Tuning Knob

The FlexRadio FlexControl is a USB tuning knob with a weighted rotary encoder and three buttons. AetherSDR detects it automatically and uses it for smooth VFO tuning with acceleration.

Requirements

• FlexControl USB tuning knob (FlexRadio accessory)
• AetherSDR built with Qt6::SerialPort support

The FlexControl is a USB serial device (VID 0x2192, PID 0x0010) that communicates at 9600 baud 8N1. No special drivers are needed — it works as a standard serial port on Linux.

Setup

Automatic Detection

By default, AetherSDR auto-detects the FlexControl on startup. When found, it opens the serial port automatically. No configuration needed — just plug it in and tune.

The auto-detect checkbox can be toggled in Radio Setup → Serial → FlexControl Tuning Knob.

Manual Connection

If auto-detect doesn't find the knob (e.g., if it was plugged in after launch):

1. Open Radio Setup → Serial
2. In the FlexControl Tuning Knob section, click Detect
3. If found, the status shows "Connected (ttyUSB0)" in green
4. Click Close to disconnect

Tuning

The rotary encoder sends tune commands with built-in acceleration:

Rotation Speed	Steps per Click	Effect
Slow	1	Tune by one step size
Medium	2–3	Tune by 2–3 steps
Fast	4–6	Tune by 4–6 steps

The step size is the same as the current tuning step shown in the RX applet (10 Hz, 100 Hz, 1 kHz, etc.). Change the step size to control the tuning resolution.

Button Actions

The FlexControl has three buttons, each supporting tap and double-tap actions. Configure them in Radio Setup → Serial → FlexControl Tuning Knob.

Default Button Mapping

Button	Tap	Double-tap
Button 1	Step Size Up	Step Size Down
Button 2	Toggle MOX	Toggle TUNE
Button 3	Toggle Mute	Toggle Lock

Available Actions

Action	Description
None	No action
StepUp	Cycle to next larger step size
StepDown	Cycle to next smaller step size
ToggleMox	Toggle transmit (MOX on/off)
ToggleTune	Toggle tune mode
ToggleMute	Toggle audio mute
ToggleLock	Toggle tune lock

Troubleshooting

FlexControl not detected

1. Check that it's plugged in: ls /dev/ttyUSB* should show a device
2. Check permissions: your user must be in the uucp group (Arch) or dialout group (Debian/Ubuntu):

   sudo usermod -aG uucp $USER  # Arch
   sudo usermod -aG dialout $USER  # Debian/Ubuntu

   Log out and back in for the group change to take effect.
3. Verify the VID/PID: lsusb | grep 2192 should show the FlexControl

Tuning is too fast or too slow

Change the step size in the RX applet. The FlexControl multiplies the step size by its acceleration factor (1–6x depending on rotation speed).

Buttons don't work

Check that the button actions are configured in Radio Setup → Serial → FlexControl section. The default actions may have been changed to "None".