Prex is an open source, royalty-free, real-time operating system for embedded systems. It is designed and implemented for resource-constrained systems that require predictable timing behavior. The highly portable code of Prex is written in 100% ANSI C based on traditional microkernel architecture.
Prex Design The Prex microkernel provides only fundamental features for task, thread, memory, IPC, exception, and synchronization. The other basic OS functions – process, file system, application loading, and networking, are provided by the user mode servers. In addition, Prex provides a POSIX emulation layer in order to utilize existing *NIX applications. This design allows the system to perform both of the native real-time task and the generic POSIX process simultaneously without degrading real-time performance. It also helps platform designers to construct OS by choosing suitable system servers for their target requisition.
Prex is royalty-free software released under Revised BSD License.
Prex has the following features:
* Task & Thread Control: preemptive priority scheduling with 256 priority levels
* Memory Management: memory protection, virtual address mapping, shared memory, MMU or MMU-less configuration
* IPC: object name space, synchronous message passing between threads
* Exception: fault trapping, framework for POSIX signal emulation
* Synchronization: semaphores, condition variables, and mutexes with priority inheritance
* Timers: sleep timers, one-shot or periodic timers
* Interrupt: nested interrupt service routines, and prioritized interrupt service threads
* Device I/O: minimum synchronous I/O interface, DPC (Deferred Procedure Call)
* Security: task capability, pathname-based access control, I/O access permission.
* Real-time: low interrupt latency, high resolution timers and scheduling priority control
* Power Management: power policy, idle thread, DVS (Dynamic Voltage Scaling)
* Debugging Facility: event logging, kernel dump, GDB remote debug
* File Systems: multi-threaded, VFS framework, buffer cache, ramfs, fatfs, arfs, etc.
* POSIX Emulation: pid, fork, exec, file I/O, signal, pipe, tty, pthread, etc.
* Libc: C library fully optimized to generate a small executable file
* CmdBox: a small binary that includes tiny versions of many UNIX utilities.
* Networking: (plan) TCP/IP stack, BSD socket interface