The Arduino UNO Q is a strange and wonderful thing: a classic Arduino for precise real-time I/O, bolted to a quad-core Qualcomm processor running full Debian Linux with a GPU. Two brains on one board. I wanted to build a proper HMI on it, in C#.

So this session builds exactly that. A real Avalonia interface running on .NET on the Linux side, driving a display, while the STM32 microcontroller reads sensors and handles buttons and hardware in real time. The two talk over Arduino's message-passing router, and our .NET app connects to it directly and becomes a first-class citizen on the bridge. A reading on a pin becomes a value on screen, and a control on screen moves something real.

The microcontroller speaks its native Arduino, the Linux side is all C#, and the two meet at the bridge. If you have ever wanted to build a real device with a real interface, this shows you how.