The Chain Key is a single-button M5Stack Chain input module with a hot-swappable blue mechanical switch, RGB status LED and UART chaining ideal for smart home controls and interactive projects. The Chain Key is a compact single-button input node in the M5Stack Chain series, designed for simple and reliable user input. It uses a hot-swappable mechanical keyboard switch with a blue tactile key, delivering clear feedback during operation. A programmable RGB LED is also built in, allowing visual status indication or interactive lighting effects. At its core, the Chain Key integrates an STM32G031G8U6 microcontroller and communicates using a UART-based serial cascading protocol. With two HY2.0-4P expansion ports, it can be easily linked with other Chain series modules to build more advanced and interactive systems. This makes it well suited to humanmachine interfaces, smart home controls, and other input-driven applications. Features M5Stack Chain series Single button input STM32G031G8U6 core MCU Hot-swappable mechanical keyboard blue switch 2x RGB LED Uses UART cascading communication protocol 2x HY2.0-4P expansion interfaces to extend Chain series devices Specifications MCU STM32G031G8U6 Input Power DC 5V Communication Interface UART Interface Spec 2x HY2.0-4P RGB LED 2x WS2812B Working Power Consumption 28.24mA Working Temperature 0 ~ 40C Product Size 23.9 x 23.9 x 34.4mm Product Weight 9.1g Resources Documents Package Contents 1 x Chain Key 1 x Chain Bridge 1 x Keycap Sticker