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
typedefunsignedcharBOOLEAN;
typedefunsignedcharINT8U;
typedefsignedcharINT8S;
typedefunsignedshortINT16U;
typedefsignedshortINT16S;
typedefunsignedintINT32U;
typedefsignedintINT32S;
typedeffloatFP32;
typedefdoubleFP64;
typedefunsignedintOS_STK;
typedefunsignedintOS_CPU_SR;
2)ARM处理器相关的宏定义
#defineOS_ENTER_CRITICAL()ARMDisableINT
#defineOS_EXIT_CRITICAL()ARMEnableINT
3)堆栈增长方向的定义
#defineOS_STK_GROWTH1
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
MRSR0,CPSR; Set IRQ and FIQ bits in CPSR to disable all interrupts
ORRR1,R0,#NO_INT
MSRCPSR_c,R1
MRSR1,CPSR; Confirm that CPSR contains the proper interrupt disable flags
ANDR1,R1,#NO_INT
CMPR1,#NO_INT
BNEOS_CPU_SR_Save; Not properly disabled (try again)
BX LR; Disabled, return the original CPSR contents in R0
ARMEnableINT
MSRCPSR_c,R0
BXLR
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
STMFDSP!, {LR}; Push return address
STMFDSP!, {LR}
STMFDSP!, {R0-R12}; Push registers
MRSR4,CPSR; Push current CPSR
TSTLR, #1; See if called from Thumb mode
ORRNER4,R4, #0x20; If yes, Set the T-bit
STMFDSP!, {R4}
LDRR4, OS_TCBCur; OSTCBCur->OSTCBStkPtr = SP;
LDRR5, [R4]
STRSP, [R5]
LDRR0,OS_TaskSwHook; OSTaskSwHook();
MOVLR, PC
BXR0
LDRR4,OS_PrioCur; OSPrioCur = OSPrioHighRdy
LDRR5,OS_PrioHighRdy
LDRBR6, [R5]
STRBR6, [R4]
LDRR4, OS_TCBCur; OSTCBCur= OSTCBHighRdy;
LDRR6, OS_TCBHighRdy
LDRR6, [R6]
STRR6, [R4]
LDRSP, [R6] ; SP = OSTCBHighRdy->OSTCBStkPtr;
;STORE NEW TASK'S CONTEXT
LDMFDSP!, {R4}; Pop new task's CPSR
MSRSPSR_cxsf, R4
LDMFDSP!, {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OSExIntExit()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
LDRR0, OS_TaskSwHook; OSTaskSwHook();
MOVLR, PC
BXR0
LDRR4, OS_PrioCur; OSPrioCur = OSPrioHighRdy
LDRR5, OS_PrioHighRdy
LDRBR6,[R5]
STRBR6,[R4]
LDRR4,OS_TCBCur ; OSTCBCur= OSTCBHighRdy;
LDRR6,OS_TCBHighRdy
LDRR6,[R6]
STRR6,[R4]
LDRSP,[R6]; SP = OSTCBHighRdy->OSTCBStkPtr;
; RESTORE NEW TASK'S CONTEXT
LDMFDSP!, {R4}; Pop new task's CPSR
MSRSPSR_cxsf, R4
LDMFDSP!, {R0-R12,LR,PC}^; Pop new task's context
②两种形式的中断程序
OS_CPU_IRQ_ISR
STMFDSP!, {R1-R3}; PUSH WORKING REGISTERS ONTO IRQ STACK
MOVR1, SP; SaveIRQ stack pointer
ADD SP, SP,#12; Adjust IRQ stack pointer
SUBR2, LR,#4; Adjust PC for return address to task
MRSR3, SPSR; Copy SPSR (i.e. interrupted task's CPSR) to R3
MSRCPSR_c, #(NO_INT | SVC32_MODE) ; Change to SVC mode
; SAVE TASK'S CONTEXT ONTO TASK'S STACK
STMFDSP!, {R2}; Push task's Return PC
STMFDSP!, {LR}; Push task's LR
STMFDSP!, {R4-R12}; Push task's R12-R4
LDMFDR1!, {R4-R6} ; Move task's R1-R3 from IRQ stack to SVC stack
STMFDSP!, {R4-R6}
STMFDSP!, {R0}; Push task's R0onto task's stack
STMFDSP!, {R3}; Push task's CPSR (i.e. IRQ's SPSR)
LDRR0,OS_IntNesting; OSIntNesting++;
LDRBR1, [R0]
ADDR1, R1,#1
STRBR1, [R0]
CMPR1, #1; if (OSIntNesting == 1) {
BNEOS_CPU_IRQ_ISR_1
LDRR4,OS_TCBCur; OSTCBCur->OSTCBStkPtr = SP
LDRR5, [R4]
STRSP, [R5]; }
OS_CPU_IRQ_ISR_1
MSRCPSR_c, #(NO_INT | IRQ32_MODE) ; Change to IRQ mode (to use the IRQ stack to handle interrupt)
LDRR0,OS_CPU_IRQ_ISR_Handler; OS_CPU_IRQ_ISR_Handler();
MOVLR, PC
BXR0
MSRCPSR_c, #(NO_INT | SVC32_MODE) ; Change to SVC mode
LDRR0,OS_IntExit; OSIntExit();
MOVLR, PC
BXR0; RESTORE NEW TASK'S CONTEXT
LDMFDSP!, {R4} ; Pop new task's CPSR
MSRSPSR_cxsf, R4
LDMFDSP!, {R0-R12,LR,PC}^; Pop new task's context
RSEG CODE:CODE:NOROOT(2)
CODE32
OS_CPU_FIQ_ISR
STMFDSP!, {R1-R3}; PUSH WORKING REGISTERS ONTO FIQ STACK
MOVR1, SP; SaveFIQ stack pointer
ADDSP, SP,#12; Adjust FIQ stack pointer
SUBR2, LR,#4; Adjust PC for return address to task
MRSR3, SPSR; Copy SPSR (i.e. interrupted task's CPSR) to R3
MSRCPSR_c, #(NO_INT | SVC32_MODE) ; Change to SVC mode
; SAVE TASK'S CONTEXT ONTO TASK'S STACK
STMFDSP!, {R2}; Push task's Return PC
STMFDSP!, {LR}; Push task's LR
STMFDSP!, {R4-R12}; Push task's R12-R4
LDMFDR1!, {R4-R6}; Move task's R1-R3 from FIQ stack to SVC stack
STMFDSP!, {R4-R6}
STMFDSP!, {R0}; Push task's R0onto task's stack
STMFDSP!, {R3}; Push task's CPSR (i.e. FIQ's SPSR)
; HANDLE NESTING COUNTER
LDRR0, OS_IntNesting; OSIntNesting++;
LDRBR1, [R0]
ADDR1, R1,#1
STRBR1, [R0]
CMPR1, #1; if (OSIntNesting == 1){
BNEOS_CPU_FIQ_ISR_1
LDRR4, OS_TCBCur; OSTCBCur->OSTCBStkPtr = SP
LDRR5, [R4]
STRSP, [R5]; }
OS_CPU_FIQ_ISR_1
MSRCPSR_c, #(NO_INT | FIQ32_MODE) ; Change to FIQ mode (to use the FIQ stack to handle interrupt)
LDRR0, ??OS_CPU_FIQ_ISR_Handler ; OS_CPU_FIQ_ISR_Handler();
MOVLR, PC
BXR0
MSRCPSR_c, #(NO_INT | SVC32_MODE) ; Change to SVC mode
LDRR0,OS_IntExit; OSIntExit();
MOVLR, PC
BXR0; RESTORE NEW TASK'S CONTEXT
LDMFDSP!, {R4}; Pop new task's CPSR
MSRSPSR_cxsf, R4
LDMFDSP!, {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
MSRCPSR_cxsf, #0xD3; Switch to SVC mode with IRQ and FIQ disabled
LDRR0, ??OS_TaskSwHook ; OSTaskSwHook();
MOVLR, PC
BXR0
LDRR4,OS_Running; OSRunning = TRUE
MOVR5, #1
STRBR5, [R4]
; SWITCH TO HIGHEST PRIORITY TASK
LDRR4,OS_TCBHighRdy;Get highest priority task TCB address
LDRR4, [R4];get stack pointer
LDRSP, [R4];switch to the new stack
LDRR4,[SP], #4;pop new task's CPSR
MSRSPSR_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_STKTaskStartStk[TASK_STK_SIZE];
OS_STKTaskStk[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
①Task1
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);
}
}
}
②Task2
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);
} |
