極小資源單片機調度器

版本二、

在IAR6.7下編譯通過。(選用：Misra C 2004)

/****小小調度器開始**********************************************/
#define MAXTASKS 3U
volatile static unsigned char timers[MAXTASKS];
#define _SS static unsigned char _lc=0U; switch(_lc){case 0U:
#define _EE break; default:break;}_lc=0U;return 255U;
#define WaitX(tickets) _lc=(unsigned char)(__LINE__)%255U+1U;if(_lc){return (tickets);}break; case ((unsigned char)(__LINE__)%255U)+1U:

#define RunTask(TaskName,TaskID)do {if (timers[(TaskID)]==0U){ timers[(TaskID)]=(TaskName)(); } } while(0)
#define RunTaskA(TaskName,TaskID) { if (timers[(TaskID)]==0U) {timers[(TaskID)]=(TaskName)(); continue;} } /*前面的任務優先保證執行*/

#define CallSub(SubTaskName) do {unsigned char currdt; _lc=(unsigned char)(__LINE__)%255U+1U; if(_lc) {return 0U;} break; case (unsigned char)(__LINE__)%255U+1U:currdt=(SubTaskName)(); if(currdt!=255U) {return currdt;}} while(0);
#define InitTasks() do {unsigned char i; for(i=MAXTASKS;i>0U ;i--) {timers[i-1U]=0U;} } while(0)
#define UpdateTimers() do { unsigned char i;for(i=MAXTASKS;i>0U ;i--){ if(timers[i-1U]!=0U){ if(timers[i-1U]!=255U) { timers[i-1U]--;} } }} while(0)

#define SEM unsigned int
/*初始化信號量*/
#define InitSem(sem) (sem)=0;
/*等待信號量*/
#define WaitSem(sem) do{ (sem)=1; WaitX(0); if ((sem)>0) return 1;} while(0);
/*等待信號量或定時器溢出， 定時器tickets 最大為0xFFFE*/
#define WaitSemX(sem,tickets)do { (sem)=(tickets)+1; WaitX(0); if((sem)>1){ (sem)--;return 1;} } while(0);
/*發送信號量*/
#define SendSem(sem)do {(sem)=0;} while(0);

/*****小小調度器結束*******************************************************/


static unsigned char task0(void){
static int i;
_SS
for(i=0;i<11;i++){
WaitX(10U);
}
_EE
}

static unsigned char task1(void){

_SS
while(1){
WaitX(10U);
}
_EE
}

static unsigned char task2(void){

_SS
while(1){
WaitX(10U);
}
_EE
}

void InitT0()
{
TMOD = 0x21;
IE |= 0x82;// 12t
TL0=0Xff;
TH0=0XDB;
TR0 = 1;
}

void INTT0(void) interrupt 1 using 1
{
TL0=0Xff; //10ms 重裝
TH0=0XDB;//b7;
UpdateTimers();

RunTask(task0,0);//任務0具有精確按時獲得執行的權限，要求：task0每次執行消耗時間<0.5個 ticket
}

int main(void)
{
InitT0();
InitTasks();
while(1){
RunTaskA(task1,1);//任務一具有比任務二優先執行的權限
RunTaskA(task2,2);
}
}