毕业设计之路(9)-ucosi操作系统移植到STM32

这个工作主要是根据网友的经验资料来学习移植的。总的来说需要下面几个参考资料。

ARM Cortex-m3权威指南

官方移植文档资料

网友移植成功经验资料

这三种资料在我的资源上传里面都能找到。

我在官网上下的是官方已经移植好的到STM32F103评估板的资料，很多部分已经实现了，所以需要改动的地方很少，不同的地方可以参考第三种网友移植成功经验资料，里面有详细说明。我下的是ucosii2.86版本。

下面说说移植过程：

移植主要涉及到两个源文件，os_cpu_c.c和os_cpu_a.asm，os_cpu.h。其他文件是ucosii核心文件，不需要修改。还有两个配置文件app_cfg.h和os_cfg.h。

整个文件框架构成图如下，用的是IAR。

这就是对照上面的说明而设置的目录结构。

下面谈主要移植的部分。主要集中在os_cpu_a.asm这个文件中，os_cpu.h主要涉及到一些宏的配置。os_cpu_c.c中主要有一个函数必须写出，就是堆栈初始化函数。

先说os_cpu.h中需要注意的地方。

下面是开关中断的宏

#define  OS_CRITICAL_METHOD   3#if OS_CRITICAL_METHOD == 3#define  OS_ENTER_CRITICAL()  {cpu_sr = OS_CPU_SR_Save();}#define  OS_EXIT_CRITICAL()   {OS_CPU_SR_Restore(cpu_sr);}#endif

CM3堆栈方向高到底递减，设置为1，还有一个任务切换的宏。

#define  OS_STK_GROWTH        1                   /* Stack grows from HIGH to LOW memory on ARM        */#define  OS_TASK_SW()         OSCtxSw()

还有几个关于systick的函数需要注释掉，下面的os_cpu_c.c会说道原因。

//                                                  /* See OS_CPU_C.C                                    *///void       OS_CPU_SysTickHandler(void);//void       OS_CPU_SysTickInit(void);////                                                  /* See BSP.C                                         *///INT32U     OS_CPU_SysTickClkFreq(void);

 

看os_cpu_c.c。

里面有些函数是钩子函数，根据需要写。如果不需要可以不写。

下面是堆栈初始化函数。

/***********************************************************************************************************                                        INITIALIZE A TASK'S STACK** Description: This function is called by either OSTaskCreate() or OSTaskCreateExt() to initialize the*              stack frame of the task being created.  This function is highly processor specific.** Arguments  : task          is a pointer to the task code**              p_arg         is a pointer to a user supplied data area that will be passed to the task*                            when the task first executes.**              ptos          is a pointer to the top of stack.  It is assumed that 'ptos' points to*                            a 'free' entry on the task stack.  If OS_STK_GROWTH is set to 1 then*                            'ptos' will contain the HIGHEST valid address of the stack.  Similarly, if*                            OS_STK_GROWTH is set to 0, the 'ptos' will contains the LOWEST valid address*                            of the stack.**              opt           specifies options that can be used to alter the behavior of OSTaskStkInit().*                            (see uCOS_II.H for OS_TASK_OPT_xxx).** Returns    : Always returns the location of the new top-of-stack once the processor registers have*              been placed on the stack in the proper order.** Note(s)    : 1) Interrupts are enabled when your task starts executing.*              2) All tasks run in Thread mode, using process stack.**********************************************************************************************************/OS_STK *OSTaskStkInit (void (*task)(void *p_arg), void *p_arg, OS_STK *ptos, INT16U opt){    OS_STK *stk;    (void)opt;                                   /* 'opt' is not used, prevent warning                 */    stk       = ptos;                            /* Load stack pointer                                 */                                                 /* Registers stacked as if auto-saved on exception    */    *(stk)    = (INT32U)0x01000000L;             /* xPSR                                               */    *(--stk)  = (INT32U)task;                    /* Entry Point                                        */    *(--stk)  = (INT32U)0xFFFFFFFEL;             /* R14 (LR) (init value will cause fault if ever used)*/    *(--stk)  = (INT32U)0x12121212L;             /* R12                                                */    *(--stk)  = (INT32U)0x03030303L;             /* R3                                                 */    *(--stk)  = (INT32U)0x02020202L;             /* R2                                                 */    *(--stk)  = (INT32U)0x01010101L;             /* R1                                                 */    *(--stk)  = (INT32U)p_arg;                   /* R0 : argument                                      */                                                 /* Remaining registers saved on process stack         */    *(--stk)  = (INT32U)0x11111111L;             /* R11                                                */    *(--stk)  = (INT32U)0x10101010L;             /* R10                                                */    *(--stk)  = (INT32U)0x09090909L;             /* R9                                                 */    *(--stk)  = (INT32U)0x08080808L;             /* R8                                                 */    *(--stk)  = (INT32U)0x07070707L;             /* R7                                                 */    *(--stk)  = (INT32U)0x06060606L;             /* R6                                                 */    *(--stk)  = (INT32U)0x05050505L;             /* R5                                                 */    *(--stk)  = (INT32U)0x04040404L;             /* R4                                                 */    return (stk);}

因为CM3支持的堆栈地址是从高到低递减的，所以里面都是--。而且CM3中断自动入栈顺序为xPSR,PC,R14,R12,R3~R0,这个可以参考CM3权威指南。所以放在前面。后面R11~R4需要我们手动入栈。最后返回栈顶指针。

OS_CPU_C.c中还有一些东西需要我们注释掉，因为官方的资料是根据评估板来写的，如果移植到我们有STM32固件库的平台上，则需要做些改变，这是参考网友移植经验知道的。这些需要注释掉的东西主要是跟systic这个定时器有关。

下面是需要注释掉的地方。

//void  OS_CPU_SysTickInit (void)//{//    INT32U  cnts;//////    cnts = OS_CPU_SysTickClkFreq() / OS_TICKS_PER_SEC;////    OS_CPU_CM3_NVIC_ST_RELOAD = (cnts - 1);//                                                 /* Enable timer.                                      *///    OS_CPU_CM3_NVIC_ST_CTRL  |= OS_CPU_CM3_NVIC_ST_CTRL_CLK_SRC | OS_CPU_CM3_NVIC_ST_CTRL_ENABLE;//                                                 /* Enable timer interrupt.                            *///    OS_CPU_CM3_NVIC_ST_CTRL  |= OS_CPU_CM3_NVIC_ST_CTRL_INTEN;//}

 

//void  OS_CPU_SysTickHandler (void)//{//    OS_CPU_SR  cpu_sr;//////    OS_ENTER_CRITICAL();                         /* Tell uC/OS-II that we are starting an ISR          *///    OSIntNesting++;//    OS_EXIT_CRITICAL();////    OSTimeTick();                                /* Call uC/OS-II's OSTimeTick()                       */////    OSIntExit();                                 /* Tell uC/OS-II that we are leaving the ISR          *///}

 

//#define  OS_CPU_CM3_NVIC_ST_CTRL    (*((volatile INT32U *)0xE000E010))   /* SysTick Ctrl & Status Reg. *///#define  OS_CPU_CM3_NVIC_ST_RELOAD  (*((volatile INT32U *)0xE000E014))   /* SysTick Reload  Value Reg. *///#define  OS_CPU_CM3_NVIC_ST_CURRENT (*((volatile INT32U *)0xE000E018))   /* SysTick Current Value Reg. *///#define  OS_CPU_CM3_NVIC_ST_CAL     (*((volatile INT32U *)0xE000E01C))   /* SysTick Cal     Value Reg. */////#define  OS_CPU_CM3_NVIC_ST_CTRL_COUNT                    0x00010000     /* Count flag.                *///#define  OS_CPU_CM3_NVIC_ST_CTRL_CLK_SRC                  0x00000004     /* Clock Source.              *///#define  OS_CPU_CM3_NVIC_ST_CTRL_INTEN                    0x00000002     /* Interrupt enable.          *///#define  OS_CPU_CM3_NVIC_ST_CTRL_ENABLE                   0x00000001     /* Counter mode.              */

os_cpu.c.c中需要注意到的地方差不多就是这些了。

下面是os_cpu_a.asm.这里面的东西最多了，也相对难理解，这就需要仔细看CM3权威指南这个资料了。

这是上面开关中断宏的汇编语言实现。

OS_CPU_SR_Save    MRS     R0, PRIMASK                                         ; Set prio int mask to mask all (except faults)    CPSID   I    BX      LROS_CPU_SR_Restore    MSR     PRIMASK, R0    BX      LR

启动最高优先级函数，只调用一次，在OSStart()中被调用。

;********************************************************************************************************;                                          START MULTITASKING;                                       void OSStartHighRdy(void);; Note(s) : 1) This function triggers a PendSV exception (essentially, causes a context switch) to cause;              the first task to start.;;           2) OSStartHighRdy() MUST:;              a) Setup PendSV exception priority to lowest;;              b) Set initial PSP to 0, to tell context switcher this is first run;;              c) Set OSRunning to TRUE;;              d) Trigger PendSV exception;;              e) Enable interrupts (tasks will run with interrupts enabled).;********************************************************************************************************OSStartHighRdy    LDR     R0, =NVIC_SYSPRI14                                  ; Set the PendSV exception priority    LDR     R1, =NVIC_PENDSV_PRI    STRB    R1, [R0]    MOVS    R0, #0                                              ; Set the PSP to 0 for initial context switch call    MSR     PSP, R0    LDR     R0, =OSRunning                                      ; OSRunning = TRUE    MOVS    R1, #1    STRB    R1, [R0]    LDR     R0, =NVIC_INT_CTRL                                  ; Trigger the PendSV exception (causes context switch)    LDR     R1, =NVIC_PENDSVSET    STR     R1, [R0]    CPSIE   I                                                   ; Enable interrupts at processor levelOSStartHang    B       OSStartHang                                         ; Should never get here

主要是手动悬起PendSV中断，设置OSRunning为1，然后开启中断之后好进入PendSV中断处理函数中进行任务切换，开始运行ucosii。PendSV这个是需要掌握的，才能理解CM3是如何实现操作系统的管理的。

下面是两个任务切换函数，一个是任务级间切换，一个是中断与任务间切换，虽然代码相同，但意义不同，这主要就跟上面说道的PendSV中断有关了。因为这个中断的存在，我们的任务切换中实现的主要工作就是触发PendSV中断，让这个中断去处理任务切换相关细节。

;********************************************************************************************************;                               PERFORM A CONTEXT SWITCH (From task level);                                           void OSCtxSw(void);; Note(s) : 1) OSCtxSw() is called when OS wants to perform a task context switch.  This function;              triggers the PendSV exception which is where the real work is done.;********************************************************************************************************OSCtxSw    LDR     R0, =NVIC_INT_CTRL                                  ; Trigger the PendSV exception (causes context switch)    LDR     R1, =NVIC_PENDSVSET    STR     R1, [R0]    BX      LR;********************************************************************************************************;                             PERFORM A CONTEXT SWITCH (From interrupt level);                                         void OSIntCtxSw(void);; Notes:    1) OSIntCtxSw() is called by OSIntExit() when it determines a context switch is needed as;              the result of an interrupt.  This function simply triggers a PendSV exception which will;              be handled when there are no more interrupts active and interrupts are enabled.;********************************************************************************************************OSIntCtxSw    LDR     R0, =NVIC_INT_CTRL                                  ; Trigger the PendSV exception (causes context switch)    LDR     R1, =NVIC_PENDSVSET    STR     R1, [R0]    BX      LR

下面就是非常重要的PendSV中断处理函数了。

;********************************************************************************************************;                                         HANDLE PendSV EXCEPTION;                                     void OS_CPU_PendSVHandler(void);; Note(s) : 1) PendSV is used to cause a context switch.  This is a recommended method for performing;              context switches with Cortex-M3.  This is because the Cortex-M3 auto-saves half of the;              processor context on any exception, and restores same on return from exception.  So only;              saving of R4-R11 is required and fixing up the stack pointers.  Using the PendSV exception;              this way means that context saving and restoring is identical whether it is initiated from;              a thread or occurs due to an interrupt or exception.;;           2) Pseudo-code is:;              a) Get the process SP, if 0 then skip (goto d) the saving part (first context switch);;              b) Save remaining regs r4-r11 on process stack;;              c) Save the process SP in its TCB, OSTCBCur->OSTCBStkPtr = SP;;              d) Call OSTaskSwHook();;              e) Get current high priority, OSPrioCur = OSPrioHighRdy;;              f) Get current ready thread TCB, OSTCBCur = OSTCBHighRdy;;              g) Get new process SP from TCB, SP = OSTCBHighRdy->OSTCBStkPtr;;              h) Restore R4-R11 from new process stack;;              i) Perform exception return which will restore remaining context.;;           3) On entry into PendSV handler:;              a) The following have been saved on the process stack (by processor):;                 xPSR, PC, LR, R12, R0-R3;              b) Processor mode is switched to Handler mode (from Thread mode);              c) Stack is Main stack (switched from Process stack);              d) OSTCBCur      points to the OS_TCB of the task to suspend;                 OSTCBHighRdy  points to the OS_TCB of the task to resume;;           4) Since PendSV is set to lowest priority in the system (by OSStartHighRdy() above), we;              know that it will only be run when no other exception or interrupt is active, and;              therefore safe to assume that context being switched out was using the process stack (PSP).;********************************************************************************************************OS_CPU_PendSVHandler    CPSID   I                                                   ; Prevent interruption during context switch    MRS     R0, PSP                                             ; PSP is process stack pointer    CBZ     R0, OS_CPU_PendSVHandler_nosave                     ; Skip register save the first time    SUBS    R0, R0, #0x20                                       ; Save remaining regs r4-11 on process stack    STM     R0, {R4-R11}    LDR     R1, =OSTCBCur                                       ; OSTCBCur->OSTCBStkPtr = SP;    LDR     R1, [R1]    STR     R0, [R1]                                            ; R0 is SP of process being switched out                                                                ; At this point, entire context of process has been savedOS_CPU_PendSVHandler_nosave    PUSH    {R14}                                               ; Save LR exc_return value    LDR     R0, =OSTaskSwHook                                   ; OSTaskSwHook();    BLX     R0    POP     {R14}    LDR     R0, =OSPrioCur                                      ; OSPrioCur = OSPrioHighRdy;    LDR     R1, =OSPrioHighRdy    LDRB    R2, [R1]    STRB    R2, [R0]    LDR     R0, =OSTCBCur                                       ; OSTCBCur  = OSTCBHighRdy;    LDR     R1, =OSTCBHighRdy    LDR     R2, [R1]    STR     R2, [R0]    LDR     R0, [R2]                                            ; R0 is new process SP; SP = OSTCBHighRdy->OSTCBStkPtr;    LDM     R0, {R4-R11}                                        ; Restore r4-11 from new process stack    ADDS    R0, R0, #0x20    MSR     PSP, R0                                             ; Load PSP with new process SP    ORR     LR, LR, #0x04                                       ; Ensure exception return uses process stack    CPSIE   I    BX      LR                                                  ; Exception return will restore remaining context    END

 

下面的说的就是上面忽略的部分systick，作为操作系统的心脏，我们需要自己来组织这个中断。

在STM32库中的终端处理文件stm32f10x_it.c中有个Systick_Handler()函数，在里面添加处理。

 

/**  * @brief  This function handles SysTick Handler.  * @param  None  * @retval None  */void SysTick_Handler(void){OSIntEnter();OSTimeTick();OSIntExit();}

在主函数main.c中添加systick初始化函数

static void Systick_init(void){RCC_ClocksTypeDef rcc_clocks;RCC_GetClocksFreq(&rcc_clocks);SysTick_Config(rcc_clocks.HCLK_Frequency / OS_TICKS_PER_SEC);}

最后还有一个需要改动的就是要把STM32启动文件中的所有PendSV_Handler替换成OS_CPU_ PendSVHandler,因为UCOS默认移植文件中使用的是OS_CPU_ PendSVHandler。