compat-uitron-configuration-faq.html

有关ecos2。0介绍了实时嵌入式的结构以及线程调度的实现和内存的管理等

></P
><P
>Some object types require initialization.  Tasks are an example of this.
You must provide a task with a priority, a function to enter when the task
starts, a name (for debugging purposes), and some memory to use for the stack.
For example (again in terms of the resulting
definitions in <TT
CLASS="FILENAME"
>pkgconf/uitron.h</TT
>):</P
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><PRE
CLASS="PROGRAMLISTING"
>#define CYGNUM_UITRON_TASKS 4           // valid task ids are 1,2,3,4
#define CYGNUM_UITRON_TASKS_INITIALLY 4 // they all exist at start

#define CYGDAT_UITRON_TASK_EXTERNS          	\
extern "C" void startup( unsigned int );    	\
extern "C" void worktask( unsigned int );   	\
extern "C" void lowtask( unsigned int );        \
static char stack1[ CYGNUM_UITRON_STACK_SIZE ], \
            stack2[ CYGNUM_UITRON_STACK_SIZE ], \
            stack3[ CYGNUM_UITRON_STACK_SIZE ], \
            stack4[ CYGNUM_UITRON_STACK_SIZE ];

#define CYGDAT_UITRON_TASK_INITIALIZERS \
 CYG_UIT_TASK("main task", 8, startup,  &amp;stack1, sizeof( stack1 )), \
 CYG_UIT_TASK("worker 2" , 9, worktask, &amp;stack2, sizeof( stack2 )), \
 CYG_UIT_TASK("worker 3" , 9, worktask, &amp;stack3, sizeof( stack3 )), \
 CYG_UIT_TASK("low task" ,20, lowtask,  &amp;stack4, sizeof( stack4 )), \&#13;</PRE
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><P
>So this example has all four tasks statically configured to exist, ready to
run, from the start of time.  The &#8220;main task&#8221; runs a routine
called <TT
CLASS="FUNCTION"
>startup()</TT
> at priority 8.  Two
&#8220;worker&#8221; tasks run both a priority 9, and a &#8220;low
priority&#8221; task runs at priority 20 to do useful non-urgent background
work.</P
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><PRE
CLASS="SCREEN"
>Task ID | Exists at | Function | Priority | Stack   | Stack
 number |  startup  |  entry   |          | address | size
--------+-----------+----------+----------+---------+----------
   1    |    Yes    |  startup |    8     | &amp;stack1 | CYGNUM...
   2    |    Yes    | worktask |    9 	  | &amp;stack2 | CYGNUM...
   3    |    Yes    | worktask |    9 	  | &amp;stack3 | CYGNUM...
   4    |    Yes    |  lowtask |   20 	  | &amp;stack4 | CYGNUM...
--------+-----------+----------+----------+---------+----------</PRE
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><P
><SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>Q: How can I create &micro;ITRON tasks in the program?</I
></SPAN
></P
><P
>You must provide free slots in the task table in which to create new tasks,
by configuring the number of tasks existing initially to be smaller than
the total.
For a task ID which does not initially exist, it will be told what routine
to call, and what priority it is, when the task is created.  But you must
still set aside memory for the task to use for its stack, and give it a
name during initialization.  For example:</P
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><PRE
CLASS="PROGRAMLISTING"
>#define CYGNUM_UITRON_TASKS 4           // valid task ids are 1-4
#define CYGNUM_UITRON_TASKS_INITIALLY 1 // only task #1 exists

#define CYGDAT_UITRON_TASK_EXTERNS \
extern "C" void startup( unsigned int ); \
static char stack1[ CYGNUM_UITRON_STACK_SIZE ], \
            stack2[ CYGNUM_UITRON_STACK_SIZE ], \
            stack3[ CYGNUM_UITRON_STACK_SIZE ], \
            stack4[ CYGNUM_UITRON_STACK_SIZE ];

#define CYGDAT_UITRON_TASK_INITIALIZERS \
   CYG_UIT_TASK( "main", 8, startup, &amp;stack1, sizeof( stack1 ) ), \
   CYG_UIT_TASK_NOEXS( "slave",      &amp;stack2, sizeof( stack2 ) ), \
   CYG_UIT_TASK_NOEXS( "slave2",     &amp;stack3, sizeof( stack3 ) ), \
   CYG_UIT_TASK_NOEXS( "slave3",     &amp;stack4, sizeof( stack4 ) ), \&#13;</PRE
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><P
>So tasks numbered 2,3 and 4 have been given their stacks during startup,
though they do not yet exist in terms of <TT
CLASS="FUNCTION"
>cre_tsk()</TT
> and
<TT
CLASS="FUNCTION"
>del_tsk()</TT
> so you can create tasks 2&#8211;4 at
runtime.</P
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><TD
><PRE
CLASS="SCREEN"
>Task ID | Exists at | Function | Priority | Stack   | Stack
 number |  startup  |  entry   |          | address | size
--------+-----------+----------+----------+---------+----------
   1    |    Yes    |  startup |    8     | &amp;stack1 | CYGNUM...
   2    |    No     |   N/A    |   N/A    | &amp;stack2 | CYGNUM...
   3    |    No     |   N/A    |   N/A    | &amp;stack3 | CYGNUM...
   4    |    No     |   N/A    |   N/A    | &amp;stack4 | CYGNUM...
--------+-----------+----------+----------+---------+----------</PRE
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><P
>(you must have at least one task at startup in order that the system can
 actually run; this is not so for other uITRON object types)</P
><P
><SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>Q: Can I have different stack sizes for &micro;ITRON tasks?</I
></SPAN
></P
><P
>Simply set aside different amounts of memory for each task to use for its
stack.  Going back to a typical default setting for the &micro;ITRON tasks,
the definitions in <TT
CLASS="FILENAME"
>pkgconf/uitron.h</TT
> might look like this:</P
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><PRE
CLASS="PROGRAMLISTING"
>#define CYGDAT_UITRON_TASK_EXTERNS \
extern "C" void task1( unsigned int ); \
extern "C" void task2( unsigned int ); \
extern "C" void task3( unsigned int ); \
extern "C" void task4( unsigned int ); \
static char stack1[ CYGNUM_UITRON_STACK_SIZE ], \
            stack2[ CYGNUM_UITRON_STACK_SIZE ], \
            stack3[ CYGNUM_UITRON_STACK_SIZE ], \
            stack4[ CYGNUM_UITRON_STACK_SIZE ];
  
#define CYGDAT_UITRON_TASK_INITIALIZERS \
  CYG_UIT_TASK( "t1", 1, task1, &amp;stack1, CYGNUM_UITRON_STACK_SIZE ), \
  CYG_UIT_TASK( "t2", 2, task2, &amp;stack2, CYGNUM_UITRON_STACK_SIZE ), \
  CYG_UIT_TASK( "t3", 3, task3, &amp;stack3, CYGNUM_UITRON_STACK_SIZE ), \
  CYG_UIT_TASK( "t4", 4, task4, &amp;stack4, CYGNUM_UITRON_STACK_SIZE )&#13;</PRE
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><P
>Note that 
<TT
CLASS="LITERAL"
>CYGNUM_UITRON_STACK_SIZE</TT
>
is used to control the size of the stack
objects themselves, and to tell the system what size stack is being provided.</P
><P
>Suppose instead stack sizes of 2000, 1000, 800 and 800 were required:
this could be achieved by using the GUI config tool to edit these
options, or editting the <TT
CLASS="FILENAME"
>.ecc</TT
> file to get these
results in <TT
CLASS="FILENAME"
>pkgconf/uitron.h</TT
>:</P
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CLASS="PROGRAMLISTING"
>#define CYGDAT_UITRON_TASK_EXTERNS \
extern "C" void task1( unsigned int ); \
extern "C" void task2( unsigned int ); \
extern "C" void task3( unsigned int ); \
extern "C" void task4( unsigned int ); \
static char stack1[ 2000 ], \
            stack2[ 1000 ], \
            stack3[  800 ], \
            stack4[  800 ];
 
#define CYGDAT_UITRON_TASK_INITIALIZERS \
      CYG_UIT_TASK( "t1", 1, task1, &amp;stack1, sizeof( stack1 ) ), \
      CYG_UIT_TASK( "t2", 2, task2, &amp;stack2, sizeof( stack2 ) ), \
      CYG_UIT_TASK( "t3", 3, task3, &amp;stack3, sizeof( stack3 ) ), \
      CYG_UIT_TASK( "t4", 4, task4, &amp;stack4, sizeof( stack4 ) )</PRE
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><P
>Note that the sizeof() operator has been used to tell the system what size
stacks are provided, rather than quoting a number (which is difficult for
maintenance) or the symbol 
<TT
CLASS="LITERAL"
>CYGNUM_UITRON_STACK_SIZE</TT
>
(which is wrong).</P
><P
>We recommend using (if available in your release) the stacksize symbols
provided in the architectural HAL for your target, called
<TT
CLASS="LITERAL"
>CYGNUM_HAL_STACK_SIZE_TYPICAL</TT
>
and 
<TT
CLASS="LITERAL"
>CYGNUM_HAL_STACK_SIZE_MINIMUM</TT
>.
So a better (more portable) version of the above might be:</P
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><PRE
CLASS="PROGRAMLISTING"
>#define CYGDAT_UITRON_TASK_EXTERNS \
extern "C" void task1( unsigned int ); \
extern "C" void task2( unsigned int ); \
extern "C" void task3( unsigned int ); \
extern "C" void task4( unsigned int ); \
static char stack1[ CYGNUM_HAL_STACK_SIZE_TYPICAL + 1200 ], \
            stack2[ CYGNUM_HAL_STACK_SIZE_TYPICAL +  200 ], \
            stack3[ CYGNUM_HAL_STACK_SIZE_TYPICAL        ], \
            stack4[ CYGNUM_HAL_STACK_SIZE_TYPICAL        ];

#define CYGDAT_UITRON_TASK_INITIALIZERS \
      CYG_UIT_TASK( "t1", 1, task1, &amp;stack1, sizeof( stack1 ) ), \
      CYG_UIT_TASK( "t2", 2, task2, &amp;stack2, sizeof( stack2 ) ), \
      CYG_UIT_TASK( "t3", 3, task3, &amp;stack3, sizeof( stack3 ) ), \
      CYG_UIT_TASK( "t4", 4, task4, &amp;stack4, sizeof( stack4 ) )</PRE
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