TNKernel was successfully ported to the Microchip (c) 16-bit microprocessors - PIC24 and dsPIC33 series.

1. The port description

   A significant changes of the TNKernel source files structure for the PIC24F/dsPIC port have been performed. All sources were rearranges according to the principle one function - one file and compiled as a library. At the linking stage of the application creating, linker takes from the library and includes in the application's output file a code only of those functions which are used in the project. It provides a significant decreasing of the ROM (FLASH) usage, what is important for the PIC24/dsPIC.
 The memory for the internal TNKernel data structures is also defined in the separate files.

This is a file names templates:

  cm_xxxx.c/h      - common
  dq_xxxx.c/h       - data queues
  ev_xxxx.c/h       - events
  mp_xxxx.c/h      - memory pools
  mx_xxxx.c/h      - mutexes
  sm_xxxx.c/h      - semaphores
  sy_xxxx.c/h       - system
  ts_xxxx.c/h        - tasks
  port_xxxx.c/h/a  - portable

 After char '_', all files names (except port parts) include:

  xx_defs.h        - definitions
  xx_extr.h        - global function prototypes
  xx_dat.c          - data memory structures declarations
  xx_fnc_xxxx.c  - functions without arguments checking
  xx_fce_xxxx.c  - functions with arguments checking
  xx_rtn_xxxx.c  - internal function

  The port part includes files:

  port_a_extr.h   - global function prototypes ( ASM-language implemented )
  port_c_extr.h   - global function prototypes ( C-language implemented )
  port_c_defs.h   - definitions( C-language )
  port_af_xxxx.s - functions ( ASM-language implemented )
  port_cf_xxxx.c  - functions ( C-language implemented )

  For the port, the single file tnkernel.h is used. If a debugging is enabled, files xx_defs.h are also in use.

2. The changes in the file tnkernel.h

   - all base types are defined
   - maximal types values are defined in the standard header file <limits.h>
   - magic numbers for the tasks, semaphores, events, etc. are placed in the corresponding xx_defs.h files
   - TN_TASK macro has been added - it decreases stack usage with the CGG attribute  __attribute__((no return))
   - TN_DEBUG macro has been added - it defines at the debugging to show the user the contents of the TCB, etc.
   - TN_NO_ERROR_CHECKING macro has been added - to use functions without arguments checking

3. The changes in the API 

 - the function tn_start_system() in the port has an arguments

      void tn_start_system(TN_UWORD * timer_task_stack,
                            TN_UWORD  timer_task_stack_size,
                            TN_UWORD * idle_task_stack,
                            TN_UWORD  idle_task_stack_size,
                            void (*app_in_cb)(void),
                            void (*cpu_int_en)(void),
                            void (*idle_user_cb)(void)
                           );
      where:

        timer_task_stack        -  timer task stack bottom address
        timer_task_stack_size -  number of timer task stack elements (not bytes)
        idle_task_stack           -  idle task stack bottom address
        idle_task_stack_size    -  number of idle task stack elements (not bytes)
        app_in_cb    -  the address of the tn_app_init() function
        cpu_int_en   -  the address of the tn_cpu_int_enable() function
        idle_user_cb - idle task callback function. This is the address of a function declared as: 
                                                                     void task_func (void * param)

  The Idle task body function looks like this:

   void tn_idle_task_func (void *par)
   {
      for(;;)
      {
         idle_user_func_callback();
         tn_idle_count++;
      }
   }

  Here idle_user_func_callback() is an idle_user_cb parameter of the tn_start_system().


   - A functions tn_sys_enter_critical() and tn_sys_exit_critical() has been added

   - In  the functions tn_start_system() and tn_task_create(), a parameter  task_stack_start must point to the stack bottom (origin). The PIC24/dsPIC stack grows from the low to the high memory addresses. For instance, if the task stack array is defined as unsigned int xxx_xxx[task_stack_size] (in C-language  notation), then the task_stack_start parameter has to be defined as &xxx_xxx[0].

4. Interrupts

    - PIC24 has a hardware control of the stack overflow, and at the context switching, the SPLIM register is also saved.

    - The file tnkernel.inc includes assembly macroes for the prologue and epilogue code of the context switching. 
      All interrupts that have to use TNKernel functions, should be processed like this:

__INT0Interrupt:
       TN_INTERRUPT_PROLOGUE
       call    _INT0_IRQ_Service
       TN_INTERRUPT_EPILOGUE

  where: 

     INT0_IRQ_Service() - C-language function with actual interrupt handler code

    When interrupts are disabled by the kernel, the only interrupts with priority 1-6 are actually blocked; interrupt with priority 7 should be never used for the TNKernel services.