建立一個(gè)屬于自己的AVR的RTOS
加入技術(shù)交流群
unsignedintOSWaitTick;//任務(wù)延時(shí)時(shí)鐘
}TCB[OS_TASKS+1];
//防止被編譯器占用
registerunsignedchartempR4asm(r4);
registerunsignedchartempR5asm(r5);
registerunsignedchartempR6asm(r6);
registerunsignedchartempR7asm(r7);
registerunsignedchartempR8asm(r8);
registerunsignedchartempR9asm(r9);
registerunsignedchartempR10asm(r10);
registerunsignedchartempR11asm(r11);
registerunsignedchartempR12asm(r12);
registerunsignedchartempR13asm(r13);
registerunsignedchartempR14asm(r14);
registerunsignedchartempR15asm(r15);
registerunsignedchartempR16asm(r16);
registerunsignedchartempR16asm(r17);
//建立任務(wù)
voidOSTaskCreate(void(*Task)(void),unsignedchar*Stack,unsignedcharTaskID)
{
unsignedchari;
*Stack--=(unsignedint)Task>>8;//將任務(wù)的地址高位壓入堆棧，
*Stack--=(unsignedint)Task;//將任務(wù)的地址低位壓入堆棧，
*Stack--=0x00;//R1__zero_reg__
*Stack--=0x00;//R0__tmp_reg__
*Stack--=0x80;//SREG在任務(wù)中，開(kāi)啟全局中斷
for(i=0;i14;i++)//在avr-libc中的FAQ中的WhatregistersareusedbytheCcompiler?
*Stack--=i;//描述了寄存器的作用
TCB[TaskID].OSTaskStackTop=(unsignedint)Stack;//將人工堆棧的棧頂，保存到堆棧的數(shù)組中
OSRdyTbl|=0x01TaskID;//任務(wù)就緒表已經(jīng)準(zhǔn)備好
}
//開(kāi)始任務(wù)調(diào)度,從最低優(yōu)先級(jí)的任務(wù)的開(kāi)始
voidOSStartTask()
{
OSTaskRunningPrio=OS_TASKS;
SP=TCB[OS_TASKS].OSTaskStackTop+17;
__asm____volatile__(retint);
}
//進(jìn)行任務(wù)調(diào)度
voidOSSched(void)
{
//根據(jù)中斷時(shí)保存寄存器的次序入棧，模擬一次中斷后，入棧的情況
__asm____volatile__(PUSH__zero_reg__nt);//R1
__asm____volatile__(PUSH__tmp_reg__nt);//R0
__asm____volatile__(IN__tmp_reg__,__SREG__nt);//保存狀態(tài)寄存器SREG
__asm____volatile__(PUSH__tmp_reg__nt);
__asm____volatile__(CLR__zero_reg__nt);//R0重新清零
__asm____volatile__(PUSHR18nt);
__asm____volatile__(PUSHR19nt);
__asm____volatile__(PUSHR20nt);
__asm____volatile__(PUSHR21nt);
__asm____volatile__(PUSHR22nt);
__asm____volatile__(PUSHR23nt);
__asm____volatile__(PUSHR24nt);
__asm____volatile__(PUSHR25nt);
__asm____volatile__(PUSHR26nt);
__asm____volatile__(PUSHR27nt);
__asm____volatile__(PUSHR30nt);
__asm____volatile__(PUSHR31nt);
__asm____volatile__(PUSHR28nt);//R28與R29用于建立在堆棧上的指針
__asm____volatile__(PUSHR29nt);//入棧完成
TCB[OSTaskRunningPrio].OSTaskStackTop=SP;//將正在運(yùn)行的任務(wù)的堆棧底保存
unsignedcharOSNextTaskID;//在現(xiàn)有堆棧上開(kāi)設(shè)新的空間
for(OSNextTaskID=0;//進(jìn)行任務(wù)調(diào)度
OSNextTaskIDOS_TASKS!(OSRdyTbl(0x01OSNextTaskID));
OSNextTaskID++);
OSTaskRunningPrio=OSNextTaskID;
cli();//保護(hù)堆棧轉(zhuǎn)換
SP=TCB[OSTaskRunningPrio].OSTaskStackTop;
sei();
//根據(jù)中斷時(shí)的出棧次序
__asm____volatile__(POPR29nt);
__asm____volatile__(POPR28nt);
__asm____volatile__(POPR31nt);
__asm____volatile__(POPR30nt);
__asm____volatile__(POPR27nt);
__asm____volatile__(POPR26nt);
__asm____volatile__(POPR25nt);
__asm____volatile__(POPR24nt);
__asm____volatile__(POPR23nt);
__asm____volatile__(POPR22nt);
__asm____volatile__(POPR21nt);
__asm____volatile__(POPR20nt);
__asm____volatile__(POPR19nt);
__asm____volatile__(POPR18nt);
__asm____volatile__(POP__tmp_reg__nt);//SERG出棧并恢復(fù)
__asm____volatile__(OUT__SREG__,__tmp_reg__nt);//
__asm____volatile__(POP__tmp_reg__nt);//R0出棧
__asm____volatile__(POP__zero_reg__nt);//R1出棧
//中斷時(shí)出棧完成
}
voidOSTimeDly(unsignedintticks)
{
if(ticks)//當(dāng)延時(shí)有效
{
OSRdyTbl=~(0x01OSTaskRunningPrio);
TCB[OSTaskRunningPrio].OSWaitTick=ticks;
OSSched();//從新調(diào)度
}
}
voidTCN0Init(void)//計(jì)時(shí)器0
{
TCCR0=0;
TCCR0|=(1CS02);//256預(yù)分頻
TIMSK|=(1TOIE0);//T0溢出中斷允許
TCNT0=100;//置計(jì)數(shù)起始值
}
SIGNAL(SIG_OVERFLOW0)
{
unsignedchari;
for(i=0;iOS_TASKS;i++)//任務(wù)時(shí)鐘
{
if(TCB[i].OSWaitTick)
{
TCB[i].OSWaitTick--;
if(TCB[i].OSWaitTick==0)//當(dāng)任務(wù)時(shí)鐘到時(shí),必須是由定時(shí)器減時(shí)的才行
{
OSRdyTbl|=(0x01i);//使任務(wù)在就緒表中置位
}
}
}
TCNT0=100;
}
voidTask0()
{
unsignedintj=0;
while(1)
{
PORTB=j++;
OSTimeDly(2);
}
}
voidTask1()
{
unsignedintj=0;
while(1)
{
PORTC=j++;
OSTimeDly(4);
}
}
voidTask2()
{
unsignedintj=0;
while(1)
{
PORTD=j++;
OSTimeDly(8);
}
}
voidTaskScheduler()
{
while(1)
{
OSSched();//反復(fù)進(jìn)行調(diào)度
}
}
intmain(void)
{
TCN0Init();
OSRdyTbl=0;
OSTaskRunningPrio=0;
OSTaskCreate(Task0,Stack[49],0);
OSTaskCreate(Task1,Stack[99],1);
OSTaskCreate(Task2,Stack[149],2);
OSTaskCreate(TaskScheduler,Stack[199],OS_TASKS);
OSStartTask();
}
在上面的例子中，一切變得很簡(jiǎn)單，三個(gè)正在運(yùn)行的主任務(wù)，都通過(guò)延時(shí)服務(wù)，主動(dòng)放棄對(duì)CPU的控制權(quán)。
在時(shí)間中斷中，對(duì)各個(gè)任務(wù)的的延時(shí)進(jìn)行計(jì)時(shí)，如果某個(gè)任務(wù)的延時(shí)結(jié)束，將任務(wù)重新在就緒表中置位。
最低級(jí)的系統(tǒng)任務(wù)TaskScheduler()，在三個(gè)主任務(wù)在放棄對(duì)CPU的控制權(quán)后開(kāi)始不斷地進(jìn)行調(diào)度。如果某個(gè)任務(wù)在就緒表中置位，通過(guò)調(diào)度，進(jìn)入最高級(jí)別的任務(wù)中繼續(xù)運(yùn)行。
第五篇：完善的協(xié)作式的內(nèi)核
現(xiàn)在為上面的協(xié)作式內(nèi)核添加一些OS中所必須的服務(wù)：
1掛起和重新運(yùn)行任務(wù)
2信號(hào)量(在必要時(shí)候，可以擴(kuò)展成郵箱和信息隊(duì)列)
3延時(shí)
#includeavr/io.h>
#includeavr/Interrupt.h>
#includeavr/signal.h>
unsignedcharStack[400];
registerunsignedcharOSRdyTblasm(r2);//任務(wù)運(yùn)行就緒表
registerunsignedcharOSTaskRunningPrioasm(r3);//正在運(yùn)行的任務(wù)
#defineOS_TASKS3//設(shè)定運(yùn)行任務(wù)的數(shù)量
structTaskCtrBlock
{
unsignedintOSTaskStackTop;//保存任務(wù)的堆棧頂
unsignedintOSWaitTick;//任務(wù)延時(shí)時(shí)鐘
}TCB[OS_TASKS+1];
//防止被編譯器占用
registerunsignedchartempR4asm(r4);
registerunsignedchartempR5asm(r5);
registerunsignedchartempR6asm(r6);
registerunsignedchartempR7asm(r7);
registerunsignedchartempR8asm(r8);
registerunsignedchartempR9asm(r9);
registerunsignedchartempR10asm(r10);
registerunsignedchartempR11asm(r11);
registerunsignedchartempR12asm(r12);
registerunsignedchartempR13asm(r13);
registerunsignedchartempR14asm(r14);
registerunsignedchartempR15asm(r15);
registerunsignedchartempR16asm(r16);
registerunsignedchartempR16asm(r17);
//建立任務(wù)
voidOSTaskCreate(void(*Task)(void),unsignedchar*Stack,unsignedcharTaskID)
{
unsignedchari;
*Stack--=(unsignedint)Task>>8;//將任務(wù)的地址高位壓入堆棧，
*Stack--=(unsignedint)Task;//將任務(wù)的地址低位壓入堆棧，
*Stack--=0x00;//R1__zero_reg__
*Stack--=0x00;//R0__tmp_reg__
*Stack--=0x80;
//SREG在任務(wù)中，開(kāi)啟全局中斷
for(i=0;i14;i++)//在avr-libc中的FAQ中的WhatregistersareusedbytheCcompiler?
*Stack--=i;//描述了寄存器的作用
TCB[TaskID].OSTaskStackTop=(unsignedint)Stack;//將人工堆棧的棧頂，保存到堆棧的數(shù)組中
OSRdyTbl|=0x01TaskID;//任務(wù)就緒表已經(jīng)準(zhǔn)備好
}
//開(kāi)始任務(wù)調(diào)度,從最低優(yōu)先級(jí)的任務(wù)的開(kāi)始
voidOSStartTask()
{
OSTaskRunningPrio=OS_TASKS;
SP=TCB[OS_TASKS].OSTaskStackTop+17;
__asm____volatile__(retint);
}
//進(jìn)行任務(wù)調(diào)度
voidOSSched(void)
{
//根據(jù)中斷時(shí)保存寄存器的次序入棧，模擬一次中斷后，入棧的情況
__asm____volatile__(PUSH__zero_reg__nt);//R1
__asm____volatile__(PUSH__tmp_reg__nt);//R0
__asm____volatile__(IN__tmp_reg__,__SREG__nt);//保存狀態(tài)寄存器SREG
__asm____volatile__(PUSH__tmp_reg__nt);
__asm____volatile__(CLR__zero_reg__nt);//R0重新清零
__asm____volatile__(PUSHR18nt);
__asm____volatile__(PUSHR19nt);
__asm____volatile__(PUSHR20nt);
__asm____volatile__(PUSHR21nt);
__asm____volatile__(PUSHR22nt);
__asm____volatile__(PUSHR23nt);
__asm____volatile__(PUSHR24nt);
__asm____volatile__(PUSHR25nt);
__asm____volatile__(PUSHR26nt);
__asm____volatile__(PUSHR27nt);
__asm____volatile__(PUSHR30nt);
__asm____volatile__(PUSHR31nt);
__asm____volatile__(PUSHR28nt);//R28與R29用于建立在堆棧上的指針
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