REXIS (Real-time EXecutive for Intelligent Systems) is a message passing executive kernel. Its main features are:

  1. Fully integrated with lwIP TCP/IP stack with MQTT (IoT) support.
  2. Round robin priority based preemptive scheduling, providing fast real-time performance.
  3. Includes both (QNX style) synchronous message passing API and asynchronous message passing API (mailboxes).
  4. Synchronous message passing primitives provide synchronizing and interprocess communication capabilities, minimizing the problem with asynchronous events and data copying.
  5. Includes mutex, binary and counting semaphores for resource access.
  6. Both synchronous message passing and mutex use priority inheritance to prevent deadlocks due to priority inversion.
  7. Mailboxes with multiple mail slots.
  8. Fast task unblocking when resource becomes available.
  9. Efficient use of Cortex MCU resources. Kernel functions run in handler mode with the system stack, and tasks run in thread/user mode with each task having its own process stack.
  10. Includes memory allocator with resource automatically tracked by the executive, and allocated resource can be reclaimed via a single kernel call.
  11. Kernel calls done with SVC instructions, context switching using PendSV, both at lowest urgency level, minimizing impact on high priority peripheral interrupts.
  12. Includes ISR safe API for task unblocking etc. from within an ISR.

More information will be available shortly. The API is documented here: 

REXIS API in browseable Doxygen format V0.90 2018/07/26 available here.

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