简单OS（ucos超级精简版）——裸调度器【worldsing笔记】

简单原则少ROM，少RAM，任务完成就让出CPU，调度器描述：

1、按最大任务数轮番调度；

2、任务调用延时接口将让出CPU使用权，进入下一个任务调度；

3、用户任务都处于延时或是不使用CPU运行Idle任务；

4、最大任务数255；

5、任务用独立栈，栈大小由用户自定义；

6、调度器无需初始化，代码为单个C文件，结构简单，代码尺寸小；

7、调度器加3个任务代码尺寸：Code=1428 RO-data=268 RW-data=32 ZI-data=520

软件环境：Keil Mdk 4.7a 硬件：stm32f103vb

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//调度器C文件 Switch.c

#include "stm32f10x.h"
#include "switch.h"
#include "string.h"
#include "stdbool.h"

TCB TaskTCB[MAX_TASK + 1] = {0};
TCB *TaskNew, *TaskRuning;
uint32_t IdleStack[20];
uint8_t TaskCnt = 0;

void TaskIdle() {
while(1){
}
}

__asm void TaskSwitch(void)
{
    LDR     R0, =0xE000ED22
    LDR     R1, =0xFF
    STRB    R1, [R0]
    LDR     R0, =0xE000ED04
    LDR     R1, =0x10000000
    STR     R1, [R0]
    BX      LR
      ALIGN
}

__asm void PendSV_Handler(void)
{
        IMPORT TaskRuning
        IMPORT TaskNew
    CPSID   I
    MRS     R0, PSP
    CBZ     R0, NoSave

SUBS R0, R0, #0x20
STM R0, {R4-R11}

    LDR     R1, =TaskRuning
    LDR     R1, [R1]
    STR     R0, [R1]
NoSave

    LDR     R0, =TaskRuning
    LDR     R1, =TaskNew
    LDR     R2, [R1]
    STR     R2, [R0]

    LDR     R0, [R2]
    LDM     R0, {R4-R11}
    ADDS    R0, R0, #0x20
    MSR     PSP, R0
    ORR     LR, LR, #0x04
    CPSIE   I
    BX      LR
    ALIGN
}

void SysTick_Handler (void)
{
      uint8_t i;
      bool bOneSwitch;
      bOneSwitch = false;
      for(i = 0; i < MAX_TASK; i++){
            if(TaskTCB[i].Delay != 0){
                TaskTCB[i].Delay--;
      }
            if(bOneSwitch == false){
              TaskCnt %= MAX_TASK;
                if(0 == TaskTCB[TaskCnt].Delay){
                    bOneSwitch = true;
                    TaskNew = &TaskTCB[TaskCnt++];
                }else{
                     TaskCnt++;
                }
          }
    }
        if(bOneSwitch == false)
            TaskNew = &TaskTCB[IDLE_TASK];
        TaskSwitch();
}

void SwitchDelay(uint16_t nTick)
{
      uint8_t i;
      if(0 == nTick)
            return;
      TaskRuning->Delay = nTick;
      for(i = 0; i < MAX_TASK; i++){
            TaskCnt %= MAX_TASK;
            if(0 == TaskTCB[TaskCnt].Delay){
                TaskNew = &TaskTCB[TaskCnt++];
                break;
            }else TaskCnt++;
    }
        if(TaskRuning == TaskNew)
            TaskNew = &TaskTCB[IDLE_TASK];
      TaskSwitch();
}

void SwitchTaskInt(void (*task)(void), OS_STK *ptos)
{
      if(MAX_TASK + 1 <= TaskCnt){
            TaskCnt = 0;
            return;
    }
      if(NULL == task)
            return;
        if(NULL == ptos)
            return;
    *(ptos)    = (INT32U)0x01000000L;
    *(--ptos) = (INT32U)task;
        TaskTCB[TaskCnt]. pTaskStack = ptos -14;
        TaskTCB[TaskCnt++]. Delay = 0;
}

void SwitchStart(void)
{
    SystemInit();
    __set_PSP(0);
    SwitchTaskInt(TaskIdle, IdleStack+19);
    SysTick_Config((SystemCoreClock / N_TICK_IN_SECOND) - 1);
}

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//调度器头文件 SWitch.h

#ifndef __SWITCH_H__
#define __SWITCH_H__

#include "stdint.h"
#define MAX_TASK 2
#define N_TICK_IN_SECOND 1000

#define IDLE_TASK MAX_TASK
typedef uint32_t OS_STK;
typedef uint32_t INT32U;

typedef struct TCB
{
uint32_t *pTaskStack;
uint16_t Delay;
}TCB;

extern TCB *TaskRuning;
extern TCB *TaskNew;
extern TCB TCBTask[MAX_TASK];

void    SwitchTaskInt(void (*task)(void), OS_STK *ptos);
void    SwitchDelay(uint16_t Time);
void    SwitchStart(void);

#endif

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//应用Demo App.c

#include    "stm32f10x.h"
#include    "stm32f10x_rcc.h"
#include    "stm32f10x_gpio.h"

#include "switch.h"
#include <stdio.h>

u32 TaskStack[2][40];

void Task0(void);
void Task1(void);

int main(void)
{
    SwitchTaskInt(Task0, &TaskStack[0][39]);
    SwitchTaskInt(Task1, &TaskStack[1][39]);
SwitchStart();
    while(1);
}

void Task0(void)
{
   u8 i;
   for(;;)
   {
     i = i;
     //SwitchDelay(200);

   }
}
void Task1(void)
{
   u8 i;
   for(;;)
   {
     //SwitchDelay(300);
     i = i;
   }
}

调度器代码： 点击下载