请教：自己写的调度程序，任务定义的变量每次重新执行都

只看该作者 · 2007-9-25 22:01

    自己写的一个基于AVR单片机（Meag16）、编译器WINAVR20070122的调度程序，基于时间片轮转法，定时器0计时，轮流让8个任务运行，切换任务时保存全部寄存器R0-R31、SREG到当前任务的堆栽，然后恢复下一个任务的现场，用中断返回指令作任务切换。设置让编译器在中断程序不保存任何寄存器，由自己保存寄存器。
    8个任务可以轮流运行，但是任务内部定义的局部在任务每次重新执行时都变为0。请教大家，谢谢了！程序代码如下：

   （1）头文件：任务控制块TCB定义、保存任务环境的入栽宏、恢复任务现场的出栽宏。
typedef struct
{
    unsigned char* task_stk_top;  //保存任务的栽顶
    unsigned char task_stack[100];//任务堆栽

}OS_TASK_TCB;

//保存所有寄存器的宏
#define pushall()
__asm__ __volatile__ ("push r1"   " ");
__asm__ __volatile__ ("push r0"   " ");
__asm__ __volatile__ ("in  r0, 0x3f"   " ");保存CPU状态寄存器
__asm__ __volatile__ ("push r0"   " ");
__asm__ __volatile__ ("eor r1, r1"   " ");WINAVR要求R1等于0
__asm__ __volatile__ ("push r2"   " ");
__asm__ __volatile__ ("push r3"   " ");
__asm__ __volatile__ ("push r4"   " ");
__asm__ __volatile__ ("push r5"   " ");
__asm__ __volatile__ ("push r6"   " ");
__asm__ __volatile__ ("push r7"   " ");
__asm__ __volatile__ ("push r8"   " ");
__asm__ __volatile__ ("push r9"   " ");
__asm__ __volatile__ ("push r10"   " ");
__asm__ __volatile__ ("push r11"   " ");
__asm__ __volatile__ ("push r12"   " ");
__asm__ __volatile__ ("push r13"   " ");
__asm__ __volatile__ ("push r14"   " ");
__asm__ __volatile__ ("push r15"   " ");
__asm__ __volatile__ ("push r16"   " ");
__asm__ __volatile__ ("push r17"   " ");
__asm__ __volatile__ ("push r18"   " ");
__asm__ __volatile__ ("push r19"   " ");
__asm__ __volatile__ ("push r20"   " ");
__asm__ __volatile__ ("push r21"   " ");
__asm__ __volatile__ ("push r22"   " ");
__asm__ __volatile__ ("push r23"   " ");
__asm__ __volatile__ ("push r24"   " ");
__asm__ __volatile__ ("push r25"   " ");
__asm__ __volatile__ ("push r26"   " ");
__asm__ __volatile__ ("push r27"   " ");
__asm__ __volatile__ ("push r28"   " ");
__asm__ __volatile__ ("push r29"   " ");
__asm__ __volatile__ ("push r30"   " ");
__asm__ __volatile__ ("push r31"   " ");

//恢复任务现场时弹出所有寄存器的宏
#define popall()
__asm__ __volatile__ ("pop r31"   " ");
__asm__ __volatile__ ("pop r30"   " ");
__asm__ __volatile__ ("pop r29"   " ");
__asm__ __volatile__ ("pop r28"   " ");
__asm__ __volatile__ ("pop r27"   " ");
__asm__ __volatile__ ("pop r26"   " ");
__asm__ __volatile__ ("pop r25"   " ");
__asm__ __volatile__ ("pop r24"   " ");
__asm__ __volatile__ ("pop r23"   " ");
__asm__ __volatile__ ("pop r22"   " ");
__asm__ __volatile__ ("pop r21"   " ");
__asm__ __volatile__ ("pop r20"   " ");
__asm__ __volatile__ ("pop r19"   " ");
__asm__ __volatile__ ("pop r18"   " ");
__asm__ __volatile__ ("pop r17"   " ");
__asm__ __volatile__ ("pop r16"   " ");
__asm__ __volatile__ ("pop r15"   " ");
__asm__ __volatile__ ("pop r14"   " ");
__asm__ __volatile__ ("pop r13"   " ");
__asm__ __volatile__ ("pop r12"   " ");
__asm__ __volatile__ ("pop r11"   " ");
__asm__ __volatile__ ("pop r10"   " ");
__asm__ __volatile__ ("pop r9"   " ");
__asm__ __volatile__ ("pop r8"   " ");
__asm__ __volatile__ ("pop r7"   " ");
__asm__ __volatile__ ("pop r6"   " ");
__asm__ __volatile__ ("pop r5"   " ");
__asm__ __volatile__ ("pop r4"   " ");
__asm__ __volatile__ ("pop r3"   " ");
__asm__ __volatile__ ("pop r2"   " ");
__asm__ __volatile__ ("pop r0"   " ");
__asm__ __volatile__ ("out 0x3f, r0"   " ");恢复CPU状态寄存器
__asm__ __volatile__ ("pop r0"   " ");
__asm__ __volatile__ ("pop r1"   " ");
__asm__ __volatile__ ("RETI"   " ");
//******************************************************************

   （2）主函数main()代码，包括8个任务，调度程序，定义8个任务，每个任务对应一个LED灯的闪烁：
#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>
#include "RTOS.h"

#define LED_PORT PORTA //LED端口定义
#define LED_DDR  DDRA
#define LED_PIN  PINA

//第1个任务定义
void task1( void )
{
    unsigned char temp ;//任务1的局部变量

    TCCR0 = 0X05;//定时器0初始化
    TIMSK = 0X01;

    TCNT0 = 0x00;
    sei();       //打开全局中断

    while(1)
    {
    //任务1每次重新执行temp都会变为0，就是这里请教大家为什么？
         temp++;

         LED_PORT ^=0X01;
    for( unsigned char i=0; i<250; i++)
    _delay_ms(10);
    }
}

//第2个任务定义
void task2(void)
{
    while(1)
    {
    LED_PORT ^=0X02;
    for( unsigned char i=0; i<250; i++)
    _delay_ms(10);
    }
}

//第3个任务定义
void task3(void)
{
    while(1)
    {
    LED_PORT ^=0X04;
    for( unsigned char i=0; i<250; i++)
    _delay_ms(10);
    }
}

//第4个任务定义
void task4(void)
{
    while(1)
    {
    LED_PORT ^=0X08;
    for( unsigned char i=0; i<250; i++)
    _delay_ms(10);
    }
}

//第5个任务定义
void task5(void)
{
    while(1)
    {
    LED_PORT ^=0X10;
    for( unsigned char i=0; i<250; i++)
    _delay_ms(10);
    }
}

//第6个任务定义
void task6(void)
{
    while(1)
    {
    LED_PORT ^=0X20;
    for( unsigned char i=0; i<250; i++)
         _delay_ms(10);
    }
}

//第7个任务定义
void task7(void)
{
    while(1)
    {
    LED_PORT ^=0X40;
    for( unsigned char i=0; i<250; i++)
    _delay_ms(10);
    }
}

//第8个任务定义
void task8(void)
{
    while(1)
    {
    LED_PORT ^=0X80;
    for( unsigned char i=0; i<250; i++)
         _delay_ms(10);
    }
}
//*******************************************************************

volatile unsigned char next_task = 0;//用来计算下一个运行的任务

//计数变量，在定时器0中断函数里加1，用来控制任务切换频率
volatile unsigned char count = 0;

volatile OS_TASK_TCB task_tcb[ 8 ];//定义8个任务的任务控制块TCB数组

//任务堆栽初始化函数，参数为：任务入口地址、任务序号（1-8）
unsigned char* stackinit( void (*task)( void ), unsigned char task_id )
{
    unsigned char* stk;
    unsigned int temp;

    temp = (unsigned int)task;//任务入口地址

    stk = &( task_tcb[task_id].task_stack[99] );//取得任务栽顶指针
    *stk-- = (unsigned char)(temp&0xff);//将任务入口地址入栽
    *stk-- = (unsigned char)(temp>>8);

    //以下是CPU所有寄存器初始化，为0值，
    *stk-- = (unsigned char)0x00;        /* R0  = 0x00 */
    *stk-- = (unsigned char)0x00;        /* R1  = 0x00 */
    *stk-- = (unsigned char)0x80;        /* R2  = 0x00 */
    *stk-- = (unsigned char)0x00;        /* R3  = 0x00 */
    *stk-- = (unsigned char)0x00;        /* R4  = 0x00 */
    *stk-- = (unsigned char)0x00;        /* R5  = 0x00 */
    *stk-- = (unsigned char)0x00;        /* R6  = 0x00 */
    *stk-- = (unsigned char)0x00;        /* R7  = 0x00 */
    *stk-- = (unsigned char)0x00;        /* R8  = 0x00 */
    *stk-- = (unsigned char)0x00;        /* R9  = 0x00 */
    *stk-- = (unsigned char)0x00;        /* R10 =      */
    *stk-- = (unsigned char)0x00;        /* R11 =      */
    *stk-- = (unsigned char)0x00;        /* R12 =      */
    *stk-- = (unsigned char)0x00;        /* R13 =      */
    *stk-- = (unsigned char)0x00;        /* R14 =      */
    *stk-- = (unsigned char)0x00;        /* R15 =      */
    *stk-- = (unsigned char)0x00;        /* R16 =      */
    *stk-- = (unsigned char)0x00;        /* R17 =      */
    *stk-- = (unsigned char)0x00;        /* R18 =      */
    *stk-- = (unsigned char)0x00;        /* R19 =      */
    *stk-- = (unsigned char)0x00;        /* R20 =      */
    *stk-- = (unsigned char)0x00;        /* R21 =      */
    *stk-- = (unsigned char)0x00;        /* R22 =      */
    *stk-- = (unsigned char)0x00;        /* R23 =      */
    *stk-- = (unsigned char)0x00;        /* R24 = 0x00 */
    *stk-- = (unsigned char)0x00;        /* R25 = 0x00 */
    *stk-- = (unsigned char)0x00;        /* R26 =      */
    *stk-- = (unsigned char)0x00;        /* R27 =      */
    *stk-- = (unsigned char)0x00;        /* R28 =      */
    *stk-- = (unsigned char)0x00;        /* R29 =      */
    *stk-- = (unsigned char)0x00;        /* R30 =      */
    *stk-- = (unsigned char)0x00;        /* R31 =      */
    *stk-- = (unsigned char)0x00;        /* SREG =    */
    return ( (unsigned char*)stk );//返回当前堆栈指针
}

//任务创建函数：
void taskcreat( void (*task)( void ), unsigned char task_id )
{
    unsigned char *temp;

    temp = stackinit( task, task_id );//堆栽初始化，并返回栽顶指针

    //初始化之后将堆栽栽顶指针保存在任务的TCB里，这个变量一直指向栽顶
    task_tcb[task_id].task_stk_top = temp;
}

void OS_Start( void )
{
    SP = task_tcb[0].task_stk_top + 33;//堆栽指针指向第一个任务

    //用中断返回指令将入口地址弹出到PC指针，运行第一个任务
    asm("RETI");
}

//定时器0的中断函数：加上下面这句，WINAVR将不保存任何寄存器
void SIG_OVERFLOW0( void ) __attribute__ ( ( signal, naked ) );
SIGNAL( SIG_OVERFLOW0 )
{
    pushall( );//自己人工保存所有寄存器

    count++;   //每次中断加1
    if(count>100)//100时任务切换，count值可以调整任务切换频率
    {
              count = 0;//重新清0

         next_task++;指向下一个任务

              //堆栽指针指向下一个任务栽顶
              SP = task_tcb[ next_task % 8 ].task_stk_top;
    }

    popall( );//人工恢复所有寄存器
}

//main()函数
int main( void )
{
    //LED灯控制端口设置
    LED_PORT=0Xff;
    LED_DDR =0Xff;

    //创建并初始化8个任务
    taskcreat( task1, 0 );
    taskcreat( task2, 1 );
    taskcreat( task3, 2 );
    taskcreat( task4, 3 );
    taskcreat( task5, 4 );
    taskcreat( task6, 5 );
    taskcreat( task7, 6 );
    taskcreat( task8, 7 );

    OS_Start( );//开始运行任务

    while( 1 );
}//****************************************************************

    我的问题就是任务1内部定义的局部变量temp为什么每次在任务1重新执行都为从0开始。这个时自己学习RTOS写的，请大家多指教！我想不断的进步，谢谢了！
    祝大家中秋快乐，工作顺心，呵呵！