HomeKit Accessory Development Kit (ADK)

HomeKitADK is Apple’s Accessory Development Kit for building HomeKit-compatible accessories in C, from tiny embedded devices to full POSIX systems. It implements the HomeKit Accessory Protocol (HAP) end-to-end, including pairing, authentication, encryption, and accessory/characteristic modeling so you can expose services like lights, locks, sensors, outlets, and bridges. The SDK factors the stack into clear layers—core protocol, transport, and platform shims—so vendors can port it to their MCU/RTOS or Linux/macOS targets with minimal changes. It provides example accessories and test harnesses that demonstrate pairing flows, event notifications, and state persistence. Discovery and session management integrate with the standard Home ecosystem, enabling accessories to be found, paired, and controlled by Apple devices with proper permissions. The ADK emphasizes reliability and certification readiness, helping manufacturers converge on behavior that passes conformance tests.