Configure FlexControl Serial Port Pin Functions

Use this page to assign a function and polarity to the DTR and RTS output pins on the serial port connected to your FlexControl or other serial-attached device. This lets AetherSDR drive external hardware — such as PTT lines or keyer inputs — through the serial port's control signals.

Before you start

• The radio must be connected. The Serial tab requires an active radio connection.
• The Serial tab is only present when AetherSDR was built with serial port support (HAVE_SERIALPORT). If you do not see a Serial tab or a Settings > FlexControl... menu item, your build does not include this feature.
• Know the device path of your serial port (for example, /dev/ttyUSB0 on Linux or COM3 on Windows).

Steps

1. Open Settings > FlexControl... — this jumps directly to the Serial tab of Radio Setup. Alternatively, open Settings > Radio Setup... and click the Serial tab.
2. In the Port combo box, select your serial device from the list. Click Refresh to rescan if your device is not shown, or type the path directly into the Path field.
3. Set the serial line parameters using the Baud, Data, Parity, and Stop combo boxes to match your device's requirements.
4. For the DTR pin, select the desired function from the DTR function combo box, then select the active polarity from the adjacent Polarity combo box.
5. For the RTS pin, repeat the same two selections — function and polarity — using the RTS function and Polarity combo boxes.
6. If your paddle connections are reversed, check Paddle Swap (swap dit/dah).
7. To have AetherSDR open this port automatically each time it starts, check Auto-open serial port on startup.
8. If you are connecting a FlexControl tuning knob, click Detect under FlexControl Tuning Knob to identify the device. Click Close to release it.
9. To have AetherSDR detect the FlexControl knob automatically on startup, check Auto-detect on startup. To reverse the tuning direction, check Invert tuning direction.

What each control does

Control	What it does	Default	Valid range / values
Port	Selects or enters the serial device path.	—	System serial ports
Refresh	Rescans for available serial ports.	—	—
Path	Editable field showing the selected port path.	—	Any valid device path
Baud	Serial baud rate.	—	Per combo box options
Data	Number of data bits.	—	Per combo box options
Parity	Parity setting.	—	Per combo box options
Stop	Number of stop bits.	—	Per combo box options
DTR: Function	Assigns a signal function to the DTR output pin.	—	Per combo box options
DTR: Polarity	Sets active-high or active-low polarity for DTR.	—	Per combo box options
RTS: Function	Assigns a signal function to the RTS output pin.	—	Per combo box options
RTS: Polarity	Sets active-high or active-low polarity for RTS.	—	Per combo box options
Paddle Swap (swap dit/dah)	Reverses dit and dah paddle inputs.	Unchecked	Checked / Unchecked
Auto-open serial port on startup	Reopens the configured port when AetherSDR launches.	Unchecked	Checked / Unchecked
FlexControl Tuning Knob: Detect	Detects a connected FlexControl knob.	—	—
FlexControl Tuning Knob: Close	Releases the FlexControl knob connection.	—	—
Auto-detect on startup	Automatically detects the FlexControl knob at launch.	Unchecked	Checked / Unchecked
Invert tuning direction	Reverses the direction of FlexControl tuning.	Unchecked	Checked / Unchecked

Firmware update changes in v0.9.3

The Radio tab firmware update workflow has changed. The Browse .ssdr... button has been renamed Select Installer... and now accepts three file types instead of only a pre-extracted .ssdr file:

• .msi — the WiX-based SmartSDR installer used by FlexRadio for firmware 4.2 and later.
• .exe — the older self-extracting SmartSDR installer.
• .ssdr — a pre-extracted firmware file (accepted as before).

The firmware stager detects the file format automatically from the first 8 bytes (OLE/MSI magic for .msi, PE/COFF MZ header for .exe) and extracts the .ssdr payload without requiring any external tools. A progress bar and status label update while the extraction runs.

In addition, the Check for Update button no longer changes into a Download button when a newer firmware version is found. Instead, when an update is available the status label instructs you to download the SmartSDR installer from flexradio.com yourself and then click Select Installer... to stage it.

Updated Radio tab firmware controls

Control	What it does	Notes
Check for Update	Queries for available firmware updates and reports the result in the status label.	When an update is found, the label directs you to download the installer from flexradio.com. The button label no longer changes to Download.
Select Installer...	Opens a file picker. Select a .msi, .exe, or .ssdr file. The stager extracts and stages the firmware automatically.	Renamed from Browse .ssdr... in v0.9.3.
Upload Firmware	Starts the firmware upload to the radio with a progress bar.	Enabled only after the stager completes extraction successfully.

Frequency calibration changes in v0.9.2.1

The RX tab frequency calibration section has been revised. Previously, the Cal Frequency (MHz) field and Start button were only shown when no GPSDO was detected. Starting in v0.9.2.1, those controls are always visible regardless of whether a GPSDO is installed.

The status message at the top of the calibration group changes depending on hardware:

• GPSDO installed — shown in green: GPSDO installed. Manual frequency offset calibration available.
• No GPSDO — shown in amber: Manual frequency offset calibration available.

The Start button now provides inline status feedback next to the button. While a calibration is in progress the button is disabled and its label changes to Busy. The status label shows the current stage (for example, Starting…) and updates as the calibration proceeds. The button is re-enabled when the calibration completes or fails.

Before starting calibration, AetherSDR now resets the stored frequency error to zero (radio set freq_error_ppb=0) before sending radio pll_start. If the Cal Frequency (MHz) field is empty when you click Start, the status label shows Enter cal frequency in amber and the calibration does not start.

Updated RX tab calibration controls

Control	What it does	Notes
Cal Frequency (MHz):	Frequency used for manual calibration.	Now always shown, with or without GPSDO.
Start	Starts the frequency calibration sweep.	Disabled and labelled Busy while active. Validates that a cal frequency has been entered before proceeding.
Freq Offset (ppb):	Manual frequency offset in parts per billion.	Reset to 0 automatically when Start is clicked.

10 MHz reference source changes in v0.9.7

The 10 MHz Reference Source: combo box on the RX tab has been updated to populate and display more accurately based on detected hardware and live oscillator state.

Previously, the combo box listed only the options corresponding to hardware detected at the time the dialog opened (TCXO, GPSDO, External), and the lock status label showed only the raw oscillator state string followed by "Locked" or "Unlocked". Starting in v0.9.7, the combo box and status label behave as follows.

Combo box population

The combo box is rebuilt dynamically. Auto is always present. Additional entries appear when any of the following is true for that source:

• The radio has reported any oscillator status (the state field is non-empty) — in this case TCXO and External 10 MHz are always included.
• The corresponding hardware is detected (tcxoPresent, gpsdoPresent, extPresent).
• The source matches the current setting or the current oscillator state.

The entry for an external reference is now labelled External 10 MHz instead of External.

The combo box selects the entry matching the radio's current oscillator setting. If that setting is not in the list, it falls back to the current combo selection, then to Auto.

Lock status label

The lock status label beside the combo box now shows a richer description:

• When oscillator status has not yet been received: Waiting for oscillator status (shown in grey/blue).
• When Auto is selected and the radio has resolved to a specific source: Auto -> \* (for example, *Auto -> GPSDO).
• When the setting and active state differ: \ -> \* (for example, *TCXO -> External 10 MHz).
• Otherwise: the active source name alone.

In all cases the lock state is appended: Locked (shown in green) or Unlocked (shown in red). If the active source is External 10 MHz but no external reference is detected, (not detected) is appended after the lock state.

The label color is green (#00c040) when locked, red (#c04040) when unlocked, and grey-blue (#8aa8c0) while waiting for status.

Updated RX tab reference source controls

Control	What it does	Notes
10 MHz Reference Source:	Selects the oscillator reference source. Sends radio oscillator <value> to the radio when changed.	Auto, TCXO, GPSDO, and External 10 MHz entries. Options shown depend on hardware detected and live oscillator state. The value ext reported by the radio is treated as equivalent to external.
Lock status label	Shows the active source, resolution of Auto, and lock state. Updates live as the radio reports oscillator state changes.	Green = Locked; Red = Unlocked; Grey-blue = waiting for status. Appends (not detected) when External 10 MHz is active but no external reference signal is present.

Slice color themes (Themes tab)

The Themes tab was added in v0.9.3 under Radio Setup. It hosts the Slice Colors section, which lets you replace the built-in AetherSDR slice colors with a fully custom per-slice palette.

Steps

1. Open Settings > Radio Setup... and click the Themes tab.
2. Select Custom colors to enable per-slice color assignment. Select Use Aether defaults to revert to the built-in palette.
3. When Custom colors is selected, click any lettered button (A through H) to open a color picker for that slice. The color takes effect immediately in VFO widgets, panadapter overlays, and CAT channel badges.
4. To revert all slices to the built-in colors, click Reset All to Defaults.

Themes tab controls

Control	What it does	Default	Notes
Use Aether defaults	Uses the built-in AetherSDR slice color palette.	Selected	Slice color buttons are disabled when this is active.
Custom colors	Enables per-slice color assignment.	—	Activates the A–H color buttons.
**Slice A–H color buttons