1. μC/OS-Ⅱ概述
μC/OS-Ⅱ在特定處理器上的移植大部分工作集中在多任務切換的實現(xiàn)上，這部分代碼主要用來保存和恢復處理器的現(xiàn)場。但許多操作如讀/寫寄存器不能用C語言而只能用匯編來實現(xiàn)。
將μC/OS-Ⅱ移植到ARM處理器上，只需要修改與處理器相關的3個文件: OS_CPU.H, OS_CPU_C.C, OS_CPU_A.ASM 。
2. OS_CPU.H的移植
1) 數(shù)據(jù)類型的定義
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處理器相關的宏定義
#define OS_ENTER_CRITICAL() ARMDisableINT
#define OS_EXIT_CRITICAL() ARMEnableINT
3) 堆棧增長方向的定義
#define OS_STK_GROWTH 1
3. OS_CPU_C.C的移植
1) 任務椎棧初始化
任務椎棧初始化函數(shù)由OSTaskCreat()或OSTaskCreatEXT()調(diào)用，用來初始化任務并返回新的堆棧指針STK.初始狀態(tài)的堆棧模擬發(fā)生一次中斷后的堆棧結(jié)構(gòu),在ARM體系結(jié)構(gòu)下，任務堆?？臻g由高到低將依次保存著PC，LR，R12…R0，CPSR，SPSR。堆棧初始化結(jié)束后，OSTaskSTKInit()返回新的堆棧棧頂指針OSTaskCreat()或OSTaskCreatEXT()將新的指針保存的OS_TCB中。
OS_STK *OSTaskStkInit (void (*task)(void *p_arg), void *p_arg, OS_STK *ptos, INT16U opt)
{
OS_STK *stk;
opt = opt; [!--empirenews.page--]
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; [!--empirenews.page--]
*--stk = unsigned int pdata;
*--stk = USER_USING_MODE|0X00;
*--stk = 0;
return (stk);
}
2) 系統(tǒng)Hook()函數(shù)
這些函數(shù)在特定的系統(tǒng)動作時被調(diào)用，允許執(zhí)行函數(shù)中的用戶代碼。這些函數(shù)默認是空函數(shù)，用戶根據(jù)實際情況添加相關代碼。
OSInitHookBegin()
OSInitHookEnd()
OSTaskCreateHook()
OSTaskDelHook()
OSTaskIdleHook()
OSTaskStatHook()
OSTaskStkInit()
OSTaskSwHook()
OSTCBInitHook()
OSTimeTickHook()
4. OS_CPU_A.ASM的移植
1) 退出臨界區(qū)和進入臨界區(qū)代碼
它們分別是退出臨界區(qū)和進入臨界區(qū)代碼的宏實現(xiàn)，主要用于在進入臨界區(qū)之前關閉中斷，在退出臨界區(qū)后恢復原來的中斷狀態(tài)。
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 [!--empirenews.page--] LR ; Disabled, return the original CPSR contents in R0
ARMEnableINT
MSR CPSR_c,R0
BX LR
2) 任務級任務切換
任務級任務切換函數(shù)OS_TasK_Sw()是當前任務因為被阻塞而主動請求CPU高度時被執(zhí)行的，由于此時的任務切換都是在非異常模式直進行的，因此區(qū)別于中斷級別的任務切換。它的工作是先將當前任務的CPU現(xiàn)場保存到該任務的堆棧中，然后獲得最高優(yōu)先級任務的堆棧指針，從該堆棧中恢復此任務的CPU現(xiàn)場，使之繼續(xù)運行，從而完成任務切換。
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
[!--empirenews.page--] 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] [!--empirenews.page--] ; 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) 中斷級任務切換函數(shù)
① 該函數(shù)由OSIntExit()和OSExIntExit()調(diào)用，它若在時鐘中斷ISR中發(fā)現(xiàn)有高優(yōu)先級任務等特的時候信號到來，則需要在中斷退出后并不返回被中斷的，的而是直接調(diào)度就緒的高高優(yōu)先級任務執(zhí)行.這樣做的目的主要是能夠盡快的讓優(yōu)先級高的任務得到響應，進而保證系統(tǒng)的實時性。
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 [!--empirenews.page--] ; 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 兩種形式的中斷程序
OS_CPU_IRQ_ISR
STMFD SP!, {R1-R3} ; PUSH WORKING REGISTERS ONTO IRQ STACK
MOV R1, SP ; Save IRQ stack pointer
ADD [!--empirenews.page--] 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} [!--empirenews.page--] ; 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
[!--empirenews.page--] 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} [!--empirenews.page--] ; 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
[!--empirenews.page--] ; 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)
[!--empirenews.page--] ; 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 [!--empirenews.page--] ; 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()函數(shù)
該函數(shù)是在OSStart()多任務啟動后，負責從最高優(yōu)先級任務的TCB控制塊中獲得該任務的堆棧指針SP通過SP依次將CPU現(xiàn)場恢復。這時系統(tǒng)就將控制權交給用戶創(chuàng)建的該任務進程，直到該任務被阻塞或者被更高優(yōu)先級的任務搶占CPU。該函數(shù)僅僅在多任務啟動時被執(zhí)行一次，用來啟動第一個也即最高優(yōu)先級任務。
OSStartHighRdy
MSR CPSR_cxsf, #0xD3 ; Switch to SVC mode with IRQ and FIQ disabled
LDR R0, ??OS_TaskSwHook [!--empirenews.page--] ; 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 [!--empirenews.page--] SP!, {R0-R12,LR,PC}^ ; pop new task's context
2. 多任務應用程序的編寫
1) C語言入口函數(shù)
函數(shù)Main()為C語言入口函數(shù)，所有C程序從這里開始運行，在該函數(shù)中進行如下操作：
③ 調(diào)用函數(shù)ARMTaskgetInit初始化ARM處理器
④ 調(diào)用OSInit初始化系統(tǒng)
⑤ 調(diào)用OSTaskCreat函數(shù)創(chuàng)建任務：Task1和Task2
⑥ 調(diào)用ARMTaskgetStart函數(shù)啟動時鐘節(jié)拍中斷
⑦ 調(diào)用OSStart啟動系統(tǒng)任務調(diào)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) 任務處理函數(shù)
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);
[!--empirenews.page--] OSTaskDel(OS_PRIO_SELF);
} |
下載文檔
