建立一个AVR的RTOS（5）—完善的协作式的内核

现在为上面的协作式内核添加一些OS中所必须的服务：

1、挂起和重新运行任务

2、信号量(在必要时候，可以扩展成邮箱和信息队列)

3、延时

#include avr/io.h>

#include

#include

unsigned char Stack[400];

register unsigned char OSRdyTbl asm("r2"); //任务运行就绪表

register unsigned char OSTaskRunningPrio asm("r3"); //正在运行的任务

#define OS_TASKS 3 //设定运行任务的数量

struct TaskCtrBlock

{

unsigned int OSTaskStackTop; //保存任务的堆栈顶

unsigned int OSWaitTick; //任务延时时钟

} TCB[OS_TASKS+1];

//防止被编译器占用

register unsigned char tempR4 asm("r4");

register unsigned char tempR5 asm("r5");

register unsigned char tempR6 asm("r6");

register unsigned char tempR7 asm("r7");

register unsigned char tempR8 asm("r8");

register unsigned char tempR9 asm("r9");

register unsigned char tempR10 asm("r10");

register unsigned char tempR11 asm("r11");

register unsigned char tempR12 asm("r12");

register unsigned char tempR13 asm("r13");

register unsigned char tempR14 asm("r14");

register unsigned char tempR15 asm("r15");

register unsigned char tempR16 asm("r16");

register unsigned char tempR16 asm("r17");

//建立任务

void OSTaskCreate(void (*Task)(void),unsigned char *Stack,unsigned char TaskID)

{

unsigned char i;

*Stack--=(unsigned int)Task>>8; //将任务的地址高位压入堆栈，

*Stack--=(unsigned int)Task; //将任务的地址低位压入堆栈，

*Stack--=0x00; //R1 __zero_reg__

*Stack--=0x00; //R0 __tmp_reg__

*Stack--=0x80;

//SREG在任务中，开启全局中断

for(i=0;i<14;i++) //在avr-libc中的FAQ中的What registers are used by the C compiler?

*Stack--=i; //描述了寄存器的作用

TCB[TaskID].OSTaskStackTop=(unsigned int)Stack; //将人工堆栈的栈顶，保存到堆栈的数组中

OSRdyTbl|=0x01

}

//开始任务调度,从最低优先级的任务的开始

void OSStartTask()

{

OSTaskRunningPrio=OS_TASKS;

SP=TCB[OS_TASKS].OSTaskStackTop+17;

__asm__ __volatile__( "reti" "\n\t" );

}

//进行任务调度

void OSSched(void)

{

//根据中断时保存寄存器的次序入栈，模拟一次中断后，入栈的情况

__asm__ __volatile__("PUSH __zero_reg__ \n\t"); //R1

__asm__ __volatile__("PUSH __tmp_reg__ \n\t"); //R0

__asm__ __volatile__("IN __tmp_reg__,__SREG__ \n\t"); //保存状态寄存器SREG

__asm__ __volatile__("PUSH __tmp_reg__ \n\t");

__asm__ __volatile__("CLR __zero_reg__ \n\t"); //R0重新清零

__asm__ __volatile__("PUSH R18 \n\t");

__asm__ __volatile__("PUSH R19 \n\t");

__asm__ __volatile__("PUSH R20 \n\t");

__asm__ __volatile__("PUSH R21 \n\t");

__asm__ __volatile__("PUSH R22 \n\t");

__asm__ __volatile__("PUSH R23 \n\t");

__asm__ __volatile__("PUSH R24 \n\t");

__asm__ __volatile__("PUSH R25 \n\t");

__asm__ __volatile__("PUSH R26 \n\t");

__asm__ __volatile__("PUSH R27 \n\t");

__asm__ __volatile__("PUSH R30 \n\t");

__asm__ __volatile__("PUSH R31 \n\t");

__asm__ __volatile__("PUSH R28 \n\t"); //R28与R29用于建立在堆栈上的指针

__asm__ __volatile__("PUSH R29 \n\t"); //入栈完成

TCB[OSTaskRunningPrio].OSTaskStackTop=SP; //将正在运行的任务的堆栈底保存

unsigned char OSNextTaskID; //在现有堆栈上开设新的空间

for (OSNextTaskID = 0; //进行任务调度

OSNextTaskID < OS_TASKS && !(OSRdyTbl & (0x01

OSNextTaskID++);

OSTaskRunningPrio = OSNextTaskID ;

cli(); //保护堆栈转换

SP=TCB[OSTaskRunningPrio].OSTaskStackTop;

sei();

//根据中断时的出栈次序

__asm__ __volatile__("POP R29 \n\t");

__asm__ __volatile__("POP R28 \n\t");

__asm__ __volatile__("POP R31 \n\t");

__asm__ __volatile__("POP R30 \n\t");

__asm__ __volatile__("POP R27 \n\t");

__asm__ __volatile__("POP R26 \n\t");

__asm__ __volatile__("POP R25 \n\t");

__asm__ __volatile__("POP R24 \n\t");

__asm__ __volatile__("POP R23 \n\t");

__asm__ __volatile__("POP R22 \n\t");

__asm__ __volatile__("POP R21 \n\t");

__asm__ __volatile__("POP R20 \n\t");

__asm__ __volatile__("POP R19 \n\t");

__asm__ __volatile__("POP R18 \n\t");

__asm__ __volatile__("POP __tmp_reg__ \n\t"); /