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Micro C/OS II 作業系統

Micro C/OS II 作業系統. Micro C/OS II 簡介. 全名： Micro-Controller Operating Systems, Version 2 參考 Jean J. Labresse, “MicroC/OS-II: The Real-Time Kernel,” CMP Book, ISBN:1-57820-103-9 http://www.uCOS-II.com. Micro C/OS II 的特性. 特性 一種嵌入式即時作業系統， C 語言寫成的

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Micro C/OS II 作業系統

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  1. Micro C/OS II 作業系統

  2. Micro C/OS II 簡介 • 全名：Micro-Controller Operating Systems, Version 2 • 參考 • Jean J. Labresse, “MicroC/OS-II: The Real-Time Kernel,” CMP Book, ISBN:1-57820-103-9 • http://www.uCOS-II.com 2

  3. Micro C/OS II 的特性 • 特性 • 一種嵌入式即時作業系統，C語言寫成的 • Preemptible priority-driven real-time scheduling. • 非常小、原始碼 5500 行，編譯後占記憶體 20KB • 非開放原始碼，亦非免費，但可取得程式碼 • 64 priority levels (max 64 tasks) • 8 reserved for uC/OS-II • Each task is an infinite loop. • Deterministic execution times for most • uC/OS-II functions and services. • Nested interrupts could go up to 256 levels. 3

  4. Supports of various 8-bit to 64-bit platforms: x86, 68x, MIPS, 8051, etc • Easy for development: Borland C++compiler and DOS (optional). • However, uC/OS-II still lacks of the following features: • Resource synchronization protocols. • Sporadic task support. • Soft-real-time support. 4

  5. Getting started with uC/OS-II! • See how a uC/OS-II program looks like. • Learn how to write a skeleton program for uC/OS-II. • How to initialize uC/OS-II? • How to create real-time tasks? • How to use inter-task communication mechanisms? • How to catch system events? 5

  6. Mail Box • A mailbox is for data exchanging between tasks. • A mailbox consists of a data pointer and a wait-list. • OSMboxPend(): • The message in the mailbox is retrieved. • If the mailbox is empty, the task is immediately blocked and moved to the wait-list. • A time-out value can be specified. • OSMboxPost(): • A message is posted in the mailbox. • If there is already a message in the mailbox, then an error is returned (not overwritten). • If tasks are waiting for a message from the mailbox, then the task with the highest priority is removed from the wait-list and scheduled to run. 6

  7. Message Queue • A message queue consists of an array of elements and a wait-list. • Different from a mailbox, a message queue can hold many data elements (in a FIFO basis). 7

  8. Hooks (User Customizable) • void OSInitHookBegin (void) • void OSInitHookEnd (void) • void OSTaskCreateHook (OS_TCB *ptcb) • void OSTaskDelHook (OS_TCB *ptcb) • void OSTaskIdleHook (void) • void OSTaskStatHook (void) • void OSTaskSwHook (void) • void OSTCBInitHook (OS_TCB *ptcb) • void OSTimeTickHook (void) 8

  9. Critical Section • A critical section is a portion of code that is not safe from race conditions because of the use of shared resources. • They can be protected by interrupt disabling/enabling interrupts or semaphores. • The use of semaphores often imposes a more significant amount of overheads. • A RTOS often use interrupts disabling/enabling to protect critical sections. • Once interrupts are disabled, neither context switches nor any other ISR’s can occur. • Interrupt latency is vital to an RTOS! • Interrupts should be disabled as short as possible to improve the responsiveness. • It must be accounted as a blocking time in the schedulability analysis. • Interrupt disabling must be used carefully: • E.g., if OSTimeDly() is called with interrupt disabled, the machine might hang! 9

  10. 背景程式 前景程式 中斷發生 Real Time System 10

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  13. 任務狀態 (Task state) • Dormant 睡眠 • Ready 備妥 • Running 執行中 • ISR 中斷 • Waiting 等待 OSStart() OSIntExit() OS_TASK_SW() 13

  14. 任務狀態圖 Waiting 等待 OSTaskDel() OSMBoxPend() OSQPend() OSSemPend() OSTaskSuspend() OSTimeDly() OSTimeDlyHMSM() ISR中斷 OSMBoxPost() OSQPost() OSPostFront() OSSemPost() OSTaskRusume() OSTaskDlyResume() OSTimeTick() Dormant 睡眠 OSIntExit OSTaskDel() 中斷 OSTaskCreate() OSTaskCreateExt() Preempted Ready 備妥 Running執行中 OSStart() OSIntExit() OS_TASK_SW() 14

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  16. TCB (Task Control Block) 16

  17. Ready List 17

  18. Ready List 18

  19. Ready List - Coding Style • Ready List • if ((OSRdyTbl[prio >> 3] &= ~OSMapTbl[prio & 0x07]) == 0)OSRdyGrp &= ~OSMapTbl[prio >> 3]; 19

  20. Task Scheduling 20

  21. Task Scheduling • A context switch must save all CPU registers and PSW of the preempted task onto its stack, and then restore the CPU registers and PSW of the highest-priority ready task from its stack. • Task-level scheduling will emulate that as if preemption/scheduling is done in an ISR. • OS_TASK_SW() will trigger a software interrupt. • The interrupt is directed to the context switch handler OSCtxSw(), which is installed when uC/OS-II is initialized. • Interrupts are disabled during the locating of the highest-priority ready task to prevent another ISR’s from making some tasks ready. 21

  22. OSSchedLock() 22

  23. OSSchedUnLock() 23

  24. Statistics Task 24

  25. Interrupts 25

  26. Initialize 26

  27. Initialize 27

  28. Starting 28

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  30. 任務函數 (1) • OSTaskCreate() • 建立任務 • OSTaskCreateExt() • 另一種建立任務的函數 • OSTaskDel() • 結束任務 • OSStart() • 啟動uCOSII系統，此時系統會由備妥佇列中取出任務執行，此函數永遠不會結束 • OSIntExit() • 系統已經離開中斷狀態，此時會從備妥的佇列中取出任務來執行。 • OS_TASK_SW() • 系統執行任務切換，此時會從備妥的佇列中取出任務來執行。 • Preempted • 目前任務被更高優先權的任無所佔，因而被切換到備妥佇列。 • Interrput • 中斷發生了，系統進入中斷服務程式。 30

  31. 任務函數 (2) • OSMBoxPend() • 任務等待訊息郵件盒，因而進入等待狀態。 • OSQPend() • 任務等待佇列。 • OSSemPend() • 任務等待號誌 (Semaphore)，拿到號誌才能取得對周邊的控制權。 • OSTaskSuspend() • 任務自行暫時擱置。 • OSTaskResume() • 任務重新開始。 • OSTimeDly() • 任務延遲一段時間，以 Time Click (時間節拍) 為單位。 • OSTimeDlyHMSM() • 任務延遲一段時間，以時、分、秒為單位。 • OSMBoxPost() • 任務收到所等待的訊息佇列盒。 • OSQPost() • 任務收到佇列。 • OSSemPost() • 任務交出號誌 Semaphore。 • OSTaskDlyResume() • uCOSII\LPC210x\CH11_uCOS-II\lpc2100\Os_cpu_a.s任務延遲取消。 31

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