FlexASIO GUI

A minimal settings panel for FlexASIO, the universal ASIO driver for Windows. Built with Python and CustomTkinter.

Features

• Independent input/output device selection — route input and output to different hardware devices, or disable either side entirely
• Backend selection — choose between Windows WASAPI, DirectSound, WDM-KS, and MME host APIs
• WASAPI Exclusive Mode toggle — enable low-latency exclusive access (automatically sets suggestedLatencySeconds = 0.0)
• Buffer size selection — 128 / 256 / 512 / 1024 / 2048 samples
• Single-instance app: launching it again focuses the existing window

Settings are written to FlexASIO.toml in your user profile folder, which FlexASIO reads on startup.

Requirements

• Windows 10/11
• FlexASIO installed to the default location (C:\Program Files\FlexASIO) — the GUI uses its bundled PortAudioDevices.exe for device enumeration

Download

From the Releases page:

• FlexASIOGUI-Setup.exe (recommended) — installs per-user (no admin prompt), adds a Start Menu shortcut, and creates a default config automatically, so no first-launch step is needed before your DAW
• FlexASIOGUI-portable.zip — unzip anywhere and run FlexASIOGUI.exe (keep the _internal folder next to the exe). For portable use, run FlexASIOGUI.exe --init once, or launch the GUI and click Apply, before first using FlexASIO in a DAW

Usage

1. Pick your backend, devices, buffer size, and exclusive mode
2. Click Apply
3. In your DAW, select FlexASIO as your ASIO driver (if audio is already running, toggle the audio device off/on to pick up changes)

The FlexASIO driver itself is loaded directly by the DAW — this GUI only edits the config file and does not need to be running while you play.

First-run setup (no GUI required)

FlexASIO reads %USERPROFILE%\FlexASIO.toml when the DAW loads the driver. To make sure that file exists before the first DAW session, run once:

FlexASIOGUI.exe --init

This silently writes a default config (WASAPI, shared mode, 256-sample buffer, default devices) and exits — it never touches an existing config. To automate it, add a RunOnce registry entry after installing (fires at next login, then removes itself):

reg add HKCU\Software\Microsoft\Windows\CurrentVersion\RunOnce /v FlexASIOInit /t REG_SZ /d "\"C:\path\to\dist\FlexASIOGUI.exe\" --init"

Or call it from an installer's post-install step.

Running from source

pip install customtkinter
python flexasio_settings.py

Building the binary

pip install pyinstaller
pyinstaller --noconsole --name FlexASIOGUI flexasio_settings.py

Files

• flexasio_settings.py — the application
• register_flexasio.bat — re-registers the FlexASIO COM server (run as admin) if the driver stops appearing in your DAW
• dist/ — prebuilt Windows binary

License

MIT