Chiisai HAL Specification

The Chiisai HAL is an open, royalty-free standard for the hardware-abstraction layer of small, cost-sensitive microcontrollers — the kind found in sensors, actuators, and other compact embedded systems. Its name comes from the Japanese word for small, reflecting its goal: to keep HAL implementations deliberately lean by focusing on the essential basic and communication functions, thereby reducing the software footprint on resource-constrained hardware.

By defining standardized interfaces and cleanly separating drivers from middleware, Chiisai makes software components reusable across different hardware platforms, regardless of the microcontroller vendor. It was developed in close collaboration with Infineon Technologies and is intended to foster an open, vendor-neutral ecosystem that lowers the barrier to developing custom HALs and connecting them to a wide range of middleware.

• About This Specification
• General
• Chiisai HAL Driver Modules
• Appendix