一个简洁实用的时间片调度法操作系统，在我的一些产品中已经应用，非常稳定，在再献给大家

//  RTOS  HEAD  FILE

#ifndef  _RTOS_T0_H
#define  _RTOS_T0_H

//  防止C编译器调用以下寄存器（可参考GCC说明），减少任务调度代码所占用的时间
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");  


#define  PUSH_ALL() \
asm  volatile( \
"PUSH R2" "
\t" \
"PUSH R3" "
\t" \
"PUSH R18" "
\t" \
"PUSH R19" "
\t" \
"PUSH R20" "
\t" \
"PUSH R21" "
\t" \
"PUSH R22" "
\t" \
"PUSH R23" "
\t" \
"PUSH R24" "
\t" \
"PUSH R25" "
\t" \
"PUSH R26" "
\t" \
"PUSH R27" "
\t" \
"PUSH R28" "
\t" \
"PUSH R29" "
\t" \
"PUSH R30" "
\t" \
"PUSH R31" "
\t" \
) \

#define POP_ALL() \
asm  volatile( \
"POP R31" "
\t" \
"POP R30" "
\t" \
"POP R29" "
\t" \
"POP R28" "
\t" \
"POP R27" "
\t" \
"POP R26" "
\t" \
"POP R25" "
\t" \
"POP R24" "
\t" \
"POP R23" "
\t" \
"POP R22" "
\t" \
"POP R21" "
\t" \
"POP R20" "
\t" \
"POP R19" "
\t" \
"POP R18" "
\t" \
"POP R3" "
\t" \
"POP R2" "
\t" \
"POP R0" "
\t" \
"OUT 0x3F,R0" "
\t" \
"POP R0" "
\t" \
"POP R1" "
\t" \
) \


#define  Total_Task_Num 8
#define  Task_Stack_Size 50
#define  Total_Stack_Size Total_Task_Num  *  Task_Stack_Size

unsigned  char  uTaskStack[Total_Stack_Size];
unsigned  char  uCurrentTaskID;
unsigned  char  uTotalTaskNum;
unsigned  char  uCurrentProperty;

unsigned  int  uTaskEntry[Total_Task_Num]; //  任务入口

void  OS_Start(void); //  开启系统：0号任务开始
void  OS_ScheduleTask(void); //  任务调度：处理任务调用属性
void  OS_CreateTask(  void  (*pTaskEntry)(void),  unsigned  char  *pTaskStack);
void  OS_Timer0Init(void); //  定时中断：调度任务
void  OS_CallNext(void);

#endif




//  RTOS.C

#include  <avr/io.h>
#include  <avr/interrupt.h>
#include  "RTOS_T0.h"

void  OS_Timer0Init(void)
{
TCNT0  =  0x00;
OCR0  =  95;

TCCR0  =  (1<<CS01); //  ti  =  F_CPU(15360000)  /  OCR0(95+1)  /  n(8)  /  2=  0.1ms

TIMSK  |=  (1<<OCIE0);
}

SIGNAL(SIG_OUTPUT_COMPARE0)
{
asm("JMP  OS_ScheduleTask");
}

void  OS_CreateTask(  void  (*pTaskEntry)(void),  unsigned  char  *pTaskStack)
{
*pTaskStack--  =  (unsigned  int)pTaskEntry;
*pTaskStack--  =  (unsigned  int)pTaskEntry>>8;

uTaskEntry[uTotalTaskNum++]  =  (unsigned  int)pTaskStack;
}

void  OS_Start(void)
{
SP  =  uTaskEntry[0];

TCNT0  =  0x00;
asm("reti");
}

//  提前调度下一任务，节约时间片资源
void  OS_CallNext(void)
{
TCNT0  =  OCR0-1;
asm("nop");
asm("nop");
asm("nop");
asm("nop");
asm("nop");
asm("nop");
asm("nop");
asm("nop");
asm("nop");
}

//  优化设置：-0s，其他形式下需要改变入栈与出栈代码

void  OS_ScheduleTask(void)
{
PUSH_ALL();

uTaskEntry[uCurrentTaskID++]  =  SP+19;
if(uCurrentTaskID  >=  uTotalTaskNum)  uCurrentTaskID  =  0;
SP  =    uTaskEntry[uCurrentTaskID]-19;

POP_ALL();

TCNT0  =  0x00;
asm("reti");
}

用如下,程序仅参考，我的系统功能如下：

芯片：mega16-16AU

A：采用PS/2键盘输入，设置设备参数
B：采用20X02LCD显示
C：扩展了32路数字输入32路数字输出（DC24V）
D：控制一套伺服
E：制三个交流感应电机
F：温度控制



#include  <avr/io.h>
#include  <util/delay.h>
#include  <avr/interrupt.h>
#include  <avr/eeprom.h>
#include  <avr/pgmspace.h>

#include  "RTOS_T0.h"



void  Task_ScanExPort(void)
{
......

TaskStart:

......

OS_CallNext();

goto  TaskStart;
}

void  Task_Keyboard(void)
{
......

TaskStart:

......

OS_CallNext();

goto  TaskStart;
}


void  Task_System(void)
{

TaskStart:

......

OS_CallNext();

goto  TaskStart;
}

void  Task_Load(void)
{
......

TaskStart:

......

OS_CallNext();

goto  TaskStart;
}

void  Task_Unload(void)
{
......

TaskStart:

......

OS_CallNext();

goto  TaskStart;
}

void  Task_LED(void)
{
......

TaskStart:

......

OS_CallNext();

goto  TaskStart;
}

void  Task_CamDisc(void)
{
......

TaskStart:

......

OS_CallNext();

goto  TaskStart;
}

void  Task_Miss_Extra(void)
{
......

TaskStart:

delay_ms(100);

OS_CallNext();

goto  TaskStart;
}


int  main(void)
{
uTotalTaskNum  =  0;
uCurrentTaskID  =  0;
OS_Timer0Init();

OS_CreateTask(Task_ScanExPort,  &uTaskStack[Total_Stack_Size-1]);

OS_CreateTask(Task_Keyboard,  &uTaskStack[Total_Stack_Size-Task_Stack_Size-1]);

OS_CreateTask(Task_System,  &uTaskStack[Total_Stack_Size-Task_Stack_Size*2-1]);

OS_CreateTask(Task_Load,  &uTaskStack[Total_Stack_Size-Task_Stack_Size*3-1]);

OS_CreateTask(Task_Unload,  &uTaskStack[Total_Stack_Size-Task_Stack_Size*4-1]);

OS_CreateTask(Task_LED,  &uTaskStack[Total_Stack_Size-Task_Stack_Size*5-1]);

OS_CreateTask(Task_CamDisc,  &uTaskStack[Total_Stack_Size-Task_Stack_Size*6-1]);

OS_CreateTask(Task_Miss_Extra,  &uTaskStack[Total_Stack_Size-Task_Stack_Size*7-1]);

OS_Start();

return(0);
}

OS_CallNext();  可以根据实际需要而删除不用