mailbox.c

一个小型化的嵌入式实时操作系统源代码

/*
; ---------------------------------------------------------------------
; File:        example1.c
;
; uC/OS Real-time multitasking kernel for the MIPS processor.
;
; Simple example of using multiple tasks and mailboxes.
;
; Created by Marco Graziano ([e-mail]).
; ----------------------------------------------------------------------
*/

#include	"ucos.h" 	/* uC/OS interface */
#include	"cpu.h"

/* allocate memory for tasks' stacks */
#define	STACKSIZE	2048
uint	Stack1[STACKSIZE];
uint	Stack2[STACKSIZE];
uint	Stack3[STACKSIZE];

/* mailbox event control blocks */
OS_EVENT *Mbox1;
OS_EVENT *Mbox2;
OS_EVENT *Mbox3;

char	MsgFrom1[] = "From 1";
char	MsgFrom2[] = "From 2";
char	MsgFrom3[] = "From 3";


/*
; ---------------------------------------------------------------
; Task 1 
; Task running at the lowest priority. 
; Wait for a message in the Box 1. Post message to Box 2.
; ---------------------------------------------------------------
 */
void
Task1(void *Id)
{
	char	*Msg;
	uint	err;
	char	buf[64];
	char	*pbuf;

	for (;;) {
		/* wait for a message from the input mailbox */
		Msg = (char *)OSMboxPend(Mbox1, 100, &err);

		/* print task's id */
		putchar( *(char*)Id );
		putchar( ',' );
		putstr( Msg );
		putchar( ',' );
		itoa( OSTimeGet(), buf, 10 );
		putstr( buf );
		putchar( '\n' );

		/* post the input message to the output mailbox */
		OSMboxPost(Mbox2, MsgFrom1);
	}
}

/*
; ---------------------------------------------------------------
; Task2
; Wait for a message in Box 2. Post message to Box 3.
; ---------------------------------------------------------------
*/
void
Task2(void *Id)
{
	char	*Msg;
	uint	err;

	for (;;) {
		/* wait for a message from the input mailbox */
		Msg = (char *)OSMboxPend(Mbox2, 100, &err);

		/* print task's id */
		putchar( *(char*)Id );
		putchar( ',' );
		putstr( Msg );
		putchar( '\n' );

		/* post the input message to the output mailbox */
		OSMboxPost(Mbox3, MsgFrom2);
	}
}


/*
; ---------------------------------------------------------------
; Task3
; Wait for a message in Box 3. Post message to Box 1.
; ---------------------------------------------------------------
*/
void
Task3(void *Id)
{
	char	*Msg;
	uint	err;

	for (;;) {
		/* wait for a message from the input mailbox */
		Msg = (char *)OSMboxPend(Mbox3, 100, &err);

		/* print task's id */
		putchar( *(char*)Id );
		putchar( ',' );
		putstr( Msg );
		putchar( '\n' );

		/* post the input message to the output mailbox */
		OSMboxPost(Mbox1, MsgFrom3);
	}
}

/*
; ---------------------------------------------------------------
 * Main function.
; ---------------------------------------------------------------
 */
int
main(int argc, char **argv)
{
	char	Id1 = '1';
	char	Id2 = '2';
	char	Id3 = '3';

	/* needed by uC/OS */
	OSInit();

	/* 
	 * create the first mailbox in the pipeline with a message 
	 * in it to get the first task started.
	 */
	Mbox1 = OSMboxCreate( "From 0" ); 

	/* create the remaining mailboxes empty */
	Mbox2 = OSMboxCreate((void *)0);
	Mbox3 = OSMboxCreate((void *)0);

	/* 
	 * create the tasks in uC/OS and assign increasing
	 * priorities to them so that Task3 at the end of
	 * the pipeline has the highest priority.
	 */
	OSTaskCreate(Task1, (void *)&Id1, (void *)&Stack1[STACKSIZE], 1);
	OSTaskCreate(Task2, (void *)&Id2, (void *)&Stack2[STACKSIZE], 2);
	OSTaskCreate(Task3, (void *)&Id3, (void *)&Stack3[STACKSIZE], 3); 

	CPUInit();
	/* start the os */
	OSStart();

	/* never reached */
} /* main */