Pre-emptive RTOS (scheduler) for PIC32 and mP/mB/mC PRO.

Features:

- Delays in tasks performed by the RTOS (using OS_Delay in stead of delay_ms), giving other tasks the possibility to execute during that waiting time.
- Binary and Counting semaphores, with or without timeout.
- Starting, stopping and replacing (stop current task, start another one) tasks.
- Signalling semaphores both from interrupts and the main thread.
- Task priorities (priority 0 being the highest one)

- Tasks are executed in the main thread, not in an interrupt routine.
- The RTOS timebase is timer 1, using interrupt priority 6 (to prevent the usage of the shadow register set). So, all timed activities have a resolution of 1 timertick. A very suitable value for 1 timertick is e.g. 1 millisecond.
- The max task execution time is 10 timerticks. This is the longest time a task will be executed, after that another task (or the same, depending on eligibility of other tasks) will be chosen for execution. If a task is pre-empted by another one the execution time will be shorter of course.
This automatic task switching every 10 timerticks can be disabled by defining a compiler directive. Doing this the RTOS becomes a CRTOS (cooperative RTOS).
- Pre-emptive (if a task with a higher priority than the current one executed becomes eligible then it gets executed first)
- Tasks with the same priority are executed in a "round Robin" (sequential with wrap around) manner.
- Idle procedure (optional)
- Stack usage measurement (optional)
- Critical sections in the tasks are possible.

Have fun!

Keywords:

- scheduler
- pre-emptive
- priority
- semaphore
 

2015-07-30: Changed the documentation (stack usage function) and the library dependancies in the package.

2015-08-06, version 1.1:

- Added the "Critical Section" procedures (Enter- and LeaveCriticalSection)
- R1 is not part of the context any more (GP never changes)
- Made the Timer1Int routine does not make any "calls" anymore (could give problems)

2015-08-09, v 1.2:

- Added OS_NO_AUTO compiler directive (in RTOS_Defines.pld) to disable automatic task switching,  setting this directive makes the system a cooperative RTOS (CRTOS)
- Always restart the 10 timerticks counter when a new task is (to be) selected
- Forced the first task selection now (in OS_Run): faster starting of first task
- Added the "Check_Events_ISR" again in the semaphore test/read routines to prevent 1 timertick delay
- Made "RestoreInterrupts" inline code. (no calls are allowed in the timebase interrupt routine)

2015-08-14:
- Added the instructions "DI" and "EHB" to the epilogue code of the OS interrupt routine.
- Fetched the interrupt Priority from the "Cause" coprocessor register to put in the "Status" register
- Added always a "rdpgpr sp, sp" to the beginning of the interrupt prologue

2015-08-16: Added the mB version of the library (not tested, only compiled). 

2015-09-20: Updated the examples: the memory manager was not initialised in them... Sorry for the inconvenience.

2015-09-21: Added, thanks to aCkO the mC for PIC32 version package (.mpkg) and the updated the zip file. I hope there is a lot of interest from the mC community!