Comtrol eCos User Manual

Page 486

Chapter 32. µITRON API

CYG_UIT_SEMA_NOEXS,

CYG_UIT_SEMA_NOEXS

Semaphore 1 will have initial count 1, semaphores 2 and 3 will be zero, number 4 will be 99 initially, 5 will be one
and numbers 6 though 10 do not exist initially.

Aside: this is how the definition of the symbol would appear in the configuration header file

pkgconf/uitron.h

—

unfortunately editing such a long, multi-line definition is somewhat cumbersome in the GUI config tool in current
releases. The macros

CYG_UIT_SEMA()

— to create a semaphore initializer — and

CYG_UIT_SEMA_NOEXS

— to

invoke a dummy initializer — are provided in in the environment to help with this. Similar macros are provided for
other object types. The resulting #define symbol is used in the context of a C++ array initializer, such as:

Cyg_Counting_Semaphore2 cyg_uitron_SEMAS[ CYGNUM_UITRON_SEMAS ] = {

CYGDAT_UITRON_SEMA_INITIALIZERS

};

which is eventually macro-processed to give

Cyg_Counting_Semaphore2 cyg_uitron_SEMAS[ 10 ] = {

Cyg_Counting_Semaphore2( ( 1 ) ),

Cyg_Counting_Semaphore2( ( 0 ) ),

Cyg_Counting_Semaphore2( ( 99 ) ),

Cyg_Counting_Semaphore2( ( 1 ) ),

Cyg_Counting_Semaphore2(0),

};

so you can see how it is necessary to include the dummy entries in that definition, otherwise the resulting code will
not compile correctly.

If you choose

CYGNUM_UITRON_SEMAS_INITIALLY

=0 it is meaningless to initialize them, for they must be created

and so initialized then, before use.

Q: What about µITRON tasks?

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

pkgconf/uitron.h

#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 ];

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