分类： 嵌入式
2011-06-28 14:16:31
| 1. μC/OS-Ⅱ概述 μC/OS-Ⅱ在特定处理器上的移植大部分工作集中在多任务切换的实现上，这部分代码主要用来保存和恢复处理器的现场。但许多操作如读/写寄存器不能用C语言而只能用汇编来实现。 将μC/OS-Ⅱ移植到ARM处理器上，只需要修改与处理器相关的3个文件: OS_CPU.H, OS_CPU_C.C, OS_CPU_A.ASM 。 2. OS_CPU.H的移植 1) 数据类型的定义 typedef unsigned char BOOLEAN; typedef unsigned char INT8U; typedef signed char INT8S; typedef unsigned short INT16U; typedef signed short INT16S; typedef unsigned int INT32U; typedef signed int INT32S; typedef float FP32; typedef double FP64; typedef unsigned int OS_STK; typedef unsigned int OS_CPU_SR; 2) ARM处理器相关的宏定义 #define OS_ENTER_CRITICAL() ARMDisableINT #define OS_EXIT_CRITICAL() ARMEnableINT 3) 堆栈增长方向的定义 #define OS_STK_GROWTH 1 3. OS_CPU_C.C的移植 1) 任务椎栈初始化 任务椎栈初始化函数由OSTaskCreat()或OSTaskCreatEXT()调用，用来初始化任务并返回新的堆栈指针STK.初始状态的堆栈模拟发生一次中断后的堆栈结构,在ARM体系结构下，任务堆栈空间由高到低将依次保存着PC，LR，R12…R0，CPSR，SPSR。堆栈初始化结束后，OSTaskSTKInit()返回新的堆栈栈顶指针OSTaskCreat()或OSTaskCreatEXT()将新的指针保存的OS_TCB中。 OS_STK *OSTaskStkInit (void (*task)(void *p_arg), void *p_arg, OS_STK *ptos, INT16U opt) { OS_STK *stk; opt = opt; stk = ptos; *stk = (OS_STK)task; *--stk = 0; *--stk = 0; *--stk = 0; *--stk = 0; *--stk = 0; *--stk = 0; *--stk = 0; *--stk = 0; *--stk = 0; *--stk = 0; *--stk = 0; *--stk = 0; *--stk = 0; *--stk = unsigned int pdata; *--stk = USER_USING_MODE|0X00; *--stk = 0; return (stk); } 2) 系统Hook()函数 这些函数在特定的系统动作时被调用，允许执行函数中的用户代码。这些函数默认是空函数，用户根据实际情况添加相关代码。 OSInitHookBegin() OSInitHookEnd() OSTaskCreateHook() OSTaskDelHook() OSTaskIdleHook() OSTaskStatHook() OSTaskStkInit() OSTaskSwHook() OSTCBInitHook() OSTimeTickHook() 4. OS_CPU_A.ASM的移植 1) 退出临界区和进入临界区代码 它们分别是退出临界区和进入临界区代码的宏实现，主要用于在进入临界区之前关闭中断，在退出临界区后恢复原来的中断状态。 ARMDisableINT MRS R0,CPSR ; Set IRQ and FIQ bits in CPSR to disable all interrupts ORR R1,R0,#NO_INT MSR CPSR_c,R1 MRS R1,CPSR ; Confirm that CPSR contains the proper interrupt disable flags AND R1,R1,#NO_INT CMP R1,#NO_INT BNE OS_CPU_SR_Save ; Not properly disabled (try again) BX LR ; Disabled, return the original CPSR contents in R0 ARMEnableINT MSR CPSR_c,R0 BX LR 2) 任务级任务切换 任务级任务切换函数OS_TasK_Sw()是当前任务因为被阻塞而主动请求CPU高度时被执行的，由于此时的任务切换都是在非异常模式直进行的，因此区别于中断级别的任务切换。它的工作是先将当前任务的CPU现场保存到该任务的堆栈中，然后获得最高优先级任务的堆栈指针，从该堆栈中恢复此任务的CPU现场，使之继续运行，从而完成任务切换。 OSCtxSw ; SAVE CURRENT TASK'S CONTEXT STMFD SP!, {LR} ; Push return address STMFD SP!, {LR} STMFD SP!, {R0-R12} ; Push registers MRS R4, CPSR ; Push current CPSR TST LR, #1 ; See if called from Thumb mode ORRNE R4, R4, #0x20 ; If yes, Set the T-bit STMFD SP!, {R4} LDR R4, OS_TCBCur ; OSTCBCur->OSTCBStkPtr = SP; LDR R5, [R4] STR SP, [R5] LDR R0, OS_TaskSwHook ; OSTaskSwHook(); MOV LR, PC BX R0 LDR R4, OS_PrioCur ; OSPrioCur = OSPrioHighRdy LDR R5, OS_PrioHighRdy LDRB R6, [R5] STRB R6, [R4] LDR R4, OS_TCBCur ; OSTCBCur = OSTCBHighRdy; LDR R6, OS_TCBHighRdy LDR R6, [R6] STR R6, [R4] LDR SP, [R6] ; SP = OSTCBHighRdy->OSTCBStkPtr; ;STORE NEW TASK'S CONTEXT LDMFD SP!, {R4} ; Pop new task's CPSR MSR SPSR_cxsf, R4 LDMFD SP!, {R0-R12,LR,PC}^ ; Pop new task's context 3) 中断级任务切换函数 ① 该函数由OSIntExit()和O***IntExit()调用，它若在时钟中断ISR中发现有高优先级任务等特的时候信号到来，则需要在中断退出后并不返回被中断的，的而是直接调度就绪的高高优先级任务执行.这样做的目的主要是能够尽快的让优先级高的任务得到响应，进而保证系统的实时性。 OSIntCtxSw LDR R0, OS_TaskSwHook ; OSTaskSwHook(); MOV LR, PC BX R0 LDR R4, OS_PrioCur ; OSPrioCur = OSPrioHighRdy LDR R5, OS_PrioHighRdy LDRB R6,[R5] STRB R6,[R4] LDR R4,OS_TCBCur ; OSTCBCur = OSTCBHighRdy; LDR R6,OS_TCBHighRdy LDR R6,[R6] STR R6,[R4] LDR SP,[R6] ; SP = OSTCBHighRdy->OSTCBStkPtr; ; RESTORE NEW TASK'S CONTEXT LDMFD SP!, {R4} ; Pop new task's CPSR MSR SPSR_cxsf, R4 LDMFD SP!, {R0-R12,LR,PC}^ ; Pop new task's context ② 两种形式的中断程序 OS_CPU_IRQ_ISR STMFD SP!, {R1-R3} ; PUSH WORKING REGISTERS ONTO IRQ STACK MOV R1, SP ; Save IRQ stack pointer ADD SP, SP,#12 ; Adjust IRQ stack pointer SUB R2, LR,#4 ; Adjust PC for return address to task MRS R3, SPSR ; Copy SPSR (i.e. interrupted task's CPSR) to R3 MSR CPSR_c, #(NO_INT | SVC32_MODE) ; Change to SVC mode ; SAVE TASK'S CONTEXT ONTO TASK'S STACK STMFD SP!, {R2} ; Push task's Return PC STMFD SP!, {LR} ; Push task's LR STMFD SP!, {R4-R12} ; Push task's R12-R4 LDMFD R1!, {R4-R6} ; Move task's R1-R3 from IRQ stack to SVC stack STMFD SP!, {R4-R6} STMFD SP!, {R0} ; Push task's R0 onto task's stack STMFD SP!, {R3} ; Push task's CPSR (i.e. IRQ's SPSR) LDR R0, OS_IntNesting ; OSIntNesting++; LDRB R1, [R0] ADD R1, R1,#1 STRB R1, [R0] CMP R1, #1 ; if (OSIntNesting == 1) { BNE OS_CPU_IRQ_ISR_1 LDR R4, OS_TCBCur ; OSTCBCur->OSTCBStkPtr = SP LDR R5, [R4] STR SP, [R5] ; } OS_CPU_IRQ_ISR_1 MSR CPSR_c, #(NO_INT | IRQ32_MODE) ; Change to IRQ mode (to use the IRQ stack to handle interrupt) LDR R0, OS_CPU_IRQ_ISR_Handler ; OS_CPU_IRQ_ISR_Handler(); MOV LR, PC BX R0 MSR CPSR_c, #(NO_INT | SVC32_MODE) ; Change to SVC mode LDR R0, OS_IntExit ; OSIntExit(); MOV LR, PC BX R0 ; RESTORE NEW TASK'S CONTEXT LDMFD SP!, {R4} ; Pop new task's CPSR MSR SPSR_cxsf, R4 LDMFD SP!, {R0-R12,LR,PC}^ ; Pop new task's context RSEG CODE:CODE:NOROOT(2) CODE32 OS_CPU_FIQ_ISR STMFD SP!, {R1-R3} ; PUSH WORKING REGISTERS ONTO FIQ STACK MOV R1, SP ; Save FIQ stack pointer ADD SP, SP,#12 ; Adjust FIQ stack pointer SUB R2, LR,#4 ; Adjust PC for return address to task MRS R3, SPSR ; Copy SPSR (i.e. interrupted task's CPSR) to R3 MSR CPSR_c, #(NO_INT | SVC32_MODE) ; Change to SVC mode ; SAVE TASK'S CONTEXT ONTO TASK'S STACK STMFD SP!, {R2} ; Push task's Return PC STMFD SP!, {LR} ; Push task's LR STMFD SP!, {R4-R12} ; Push task's R12-R4 LDMFD R1!, {R4-R6} ; Move task's R1-R3 from FIQ stack to SVC stack STMFD SP!, {R4-R6} STMFD SP!, {R0} ; Push task's R0 onto task's stack STMFD SP!, {R3} ; Push task's CPSR (i.e. FIQ's SPSR) ; HANDLE NESTING COUNTER LDR R0, OS_IntNesting ; OSIntNesting++; LDRB R1, [R0] ADD R1, R1,#1 STRB R1, [R0] CMP R1, #1 ; if (OSIntNesting == 1){ BNE OS_CPU_FIQ_ISR_1 LDR R4, OS_TCBCur ; OSTCBCur->OSTCBStkPtr = SP LDR R5, [R4] STR SP, [R5] ; } OS_CPU_FIQ_ISR_1 MSR CPSR_c, #(NO_INT | FIQ32_MODE) ; Change to FIQ mode (to use the FIQ stack to handle interrupt) LDR R0, ??OS_CPU_FIQ_ISR_Handler ; OS_CPU_FIQ_ISR_Handler(); MOV LR, PC BX R0 MSR CPSR_c, #(NO_INT | SVC32_MODE) ; Change to SVC mode LDR R0, OS_IntExit ; OSIntExit(); MOV LR, PC BX R0 ; RESTORE NEW TASK'S CONTEXT LDMFD SP!, {R4} ; Pop new task's CPSR MSR SPSR_cxsf, R4 LDMFD SP!, {R0-R12,LR,PC}^ ; Pop new task's context 4) OSStartHighRdy()函数 该函数是在OSStart()多任务启动后，负责从最高优先级任务的TCB控制块中获得该任务的堆栈指针SP通过SP依次将CPU现场恢复。这时系统就将控制权交给用户创建的该任务进程，直到该任务被阻塞或者被更高优先级的任务抢占CPU。该函数仅仅在多任务启动时被执行一次，用来启动第一个也即最高优先级任务。 OSStartHighRdy MSR CPSR_cxsf, #0xD3 ; Switch to SVC mode with IRQ and FIQ disabled LDR R0, ??OS_TaskSwHook ; OSTaskSwHook(); MOV LR, PC BX R0 LDR R4, OS_Running ; OSRunning = TRUE MOV R5, #1 STRB R5, [R4] ; SWITCH TO HIGHEST PRIORITY TASK LDR R4, OS_TCBHighRdy ; Get highest priority task TCB address LDR R4, [R4] ; get stack pointer LDR SP, [R4] ; switch to the new stack LDR R4, [SP], #4 ; pop new task's CPSR MSR SPSR_cxsf,R4 LDMFD SP!, {R0-R12,LR,PC}^ ; pop new task's context 2. 多任务应用程序的编写 1) C语言入口函数 函数Main()为C语言入口函数，所有C程序从这里开始运行，在该函数中进行如下操作： ③ 调用函数ARMTaskgetInit初始化ARM处理器 ④ 调用OSInit初始化系统 ⑤ 调用OSTaskCreat函数创建任务：Task1和Task2 ⑥ 调用ARMTaskgetStart函数启动时钟节拍中断 ⑦ 调用OSStart启动系统任务调度 ＃i nclude “config.h” OS_STK TaskStartStk[TASK_STK_SIZE]; OS_STK TaskStk[TASK_STK_SIZE]; int Main(void){ OSInit(); OSTaskCreate(Task1,(void*)0,&TaskStartStk[TASK_STK_SIZE-1],0); OSStart(); return(); } 2) 任务处理函数 ① Task1 void Task1(void *pdata){ pdata=pdata; TargetInit(); For(;;){ OSTimeDly(OS_TICKS_PER_SEC/50); If(GetKey()!=KEY1) { continue; } OSTaskCreate(Task2,(void *)0,&TaskStk[TASK_STK_SIZE-1],10); While(GetKey()!=0) { OSTimeDly(OS_TICKS_PER_SEC/50); } } } ② Task2 void Task2(void *pdata){ pdata=pdata; BeeMoo(); OSTimeDly(OS_TICKS_PER_SEC/8); BeeMoo(); OSTimeDly(OS_TICKS_PER_SEC/4); BeeMoo(); OSTimeDly(OS_TICKS_PER_SEC/8); OSTaskDel(OS_PRIO_SELF); } |
