GlowSync — ambient light for Skydimo and Adalight LED strips on Windows

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The LED strip behind your monitor mirrors the colors at the edges of the screen, dances to music or runs effects. GlowSync is a lightweight, open-source replacement for the official Skydimo app (and an Ambilight-style alternative to Prismatik / HyperHDR for DIY Adalight strips). It lives in the tray, never pops up on its own and turns the strip off together with the monitor.

⬇ Download GlowSync.exe · Windows 10 (1903+) / 11 · free, MIT

The interface is in Russian for now.

Features

• Screen sync via DXGI Desktop Duplication. The frame is downscaled on the GPU, CPU load is about 0.1 %. Settings: 10–60 fps, smoothing, saturation, gamma, capture depth, blending of neighbouring LEDs, black threshold, automatic letterbox (black bar) detection for widescreen movies (subtitles in the bar do not confuse it).

• Music mode: audio is taken from the playback device (WASAPI loopback, no microphone needed): spectrum, pulse, VU meter. Switching between headphones and speakers is picked up automatically.

• Effects: rainbow, color cycle, breathing, solid color, comet.

• Turns off with the monitor, detected two independent ways, because one is not enough:

  1. Windows display-state notifications (console display state, session display status, monitor power);
  2. polling the monitor itself over DDC/CI (VCP 0xD6) every 2 seconds. This catches the monitor being switched off with its own power button, which Windows does not report at all.

  A monitor that does not answer DDC/CI never turns the strip off by itself, and neither does a single missed answer (three in a row are needed). Turning off applies after the screen has been dark for more than 2 seconds, turning on is instant: this handles monitors that blink on and off a dozen times while going to sleep. The strip also goes dark on sleep and shutdown and, optionally, on lock (Win + L).

• Night mode: brightness limit on a schedule. White balance R/G/B if the strip looks too blue.

• Global hotkeys with an unobtrusive on-screen hint that does not steal focus from games.

• Auto-detect and auto-reconnect: unplugged USB, sleep, port busy with another program: it reconnects without a restart. Bluetooth COM ports are skipped (probing them freezes the system for seconds).

• Layout editor (LEDs per side, start corner, direction, offset) and a side test.

• One-click import of Skydimo settings: brightness, mode, layout, frame rate, hotkeys.

• Log is capped at 1 MB (Skydimo's logs were known to grow to 15 GB).

Requirements

• Windows 10 (1903+) or Windows 11.
• .NET 8 Desktop Runtime. If it is missing, Windows offers to download it on first launch.
• A Skydimo LED strip (tested on SK0127, 65 LEDs, CH340 USB chip), or any DIY strip running Adalight firmware (Arduino, ESP8266/ESP32 and similar).

Install

Prebuilt exe: download GlowSync.exe, put it in any folder and run it. It adds itself to autostart (silent, tray only) and finds the strip on a USB port.

From source:

git clone https://github.com/skybots-tg/glowsync.git
cd glowsync
.\install.ps1

install.ps1 builds the project, installs it to %LOCALAPPDATA%\Programs\GlowSync, creates a Start menu shortcut and launches it. The same command updates an existing install.

Command-line options: --autostart starts silently in the tray (this is how autostart is registered), --exit closes a running instance.

Files: settings in %LOCALAPPDATA%\GlowSync\config.json, logs in %LOCALAPPDATA%\GlowSync\logs.

Default hotkeys

Action	Keys
Toggle the light	Ctrl + Alt + Shift + F10
Brighter / dimmer	Ctrl + Alt + Shift + ↑ / ↓
Next / previous mode	Ctrl + Alt + Shift + → / ←

They can be changed in the settings, on the «Поведение» (Behaviour) tab.

Troubleshooting

Symptom	Cause and fix
"COM port is busy with another program"	Skydimo or other LED software is running. Settings → «Поведение» has a button that closes Skydimo and removes it from autostart (reversible).
The strip does not turn off with the monitor	On the «Поведение» tab, check that the monitor answers DDC/CI. If it says it has not answered yet, enable DDC/CI in the monitor's own menu.
Device not found	Install the USB-serial driver (CH340 for Skydimo). The strip must show up as a COM port in Device Manager.
Colors are in the wrong places	«Лента и устройство» (Strip and device) tab → side test: left is red, top green, right blue, bottom yellow, the first LED white. Adjust start and direction.
Dark movie scenes flicker	Increase the black threshold and smoothing on the «Экран» (Screen) tab.
Black screen on browser video	DRM-protected content (Netflix and similar) is excluded from screen capture by Windows itself.

Skydimo protocol

Useful if you are writing your own software: Skydimo controllers are Adalight with a different frame header.

• Port: 115200 baud, 8N1.
• Handshake: send Moni-A, the reply is SK0127, + 7 bytes of serial number + \r\n (those bytes may contain 0x0D and 0x0A, so do not parse it line by line).
• Frame: 'A' 'd' 'a' 0x00 <count_hi> <count_lo> followed by count × RGB, 3 bytes per LED. Classic Adalight differs: 'A' 'd' 'a' + (count-1) + checksum byte hi ^ lo ^ 0x55.
• The controller expects exactly as many LEDs as its model has (65 for SK0127).
• Capture zones: the screen is split into a grid (31×17 for SK0127), each LED takes the average of its cell, then gamma 2.2 is applied. The result is indistinguishable from the official app (checked against real Skydimo output: difference ≤ 2 of 255).

Development

dotnet build GlowSync.sln
dotnet build tests -o $env:TEMP\gs-tests; & $env:TEMP\gs-tests\GlowSync.Tests.exe

Tests cover the layout generator (compared with Skydimo's maps if it is installed), controller reply parsing, settings import, the zone sampler (against reference Skydimo output on a gradient), letterbox detection, the night schedule, monitor polling logic and real GPU screen capture.

Pitfalls worth knowing if you build something similar:

• Vortice 3.8: the IDXGIOutput5.DuplicateOutput1 wrapper crashes the process with an AccessViolation, so the method is called directly through the vtable (see DesktopCapture.DuplicateOutput1).
• POWERBROADCAST_SETTING carries exactly one data byte after the GUID and length. Reading it as a 32-bit value pulls garbage from the buffer into the high bytes, and "display off" turns into "on" (see SystemEvents.OnPowerSettingChange).
• System.IO.Ports is deliberately not used: its background thread crashes the process if the USB adapter is unplugged while the port is open. A thin wrapper over CreateFile/WriteFile is used instead.

License

MIT. Do whatever you want, no warranty.