嵌入式实时操作系统UC-OS-III用户手册

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"嵌入式实时操作系统UC-OS-III，由Jean J. Labrosse编写，是一本关于实时内核的用户手册，详细介绍了如何使用和理解µC/OS-II。" 嵌入式实时操作系统UC-OS-III是专为微控制器设计的一种轻量级、高效的操作系统，适用于各种嵌入式应用。它提供了必要的功能，如任务管理、时间管理、信号量管理、互斥信号量、事件标志、消息邮箱和消息队列等，以支持实时系统的运行。 1. µC/OS-II User Manual：这本手册的前言部分可能介绍了作者和出版信息，以及手册的目的和目标读者。开始部分向读者提供了一个逐步引导，帮助他们快速上手µC/OS-II的使用。 2. 实时系统概念：这部分详细解释了实时系统的基本概念，包括硬实时和软实时的区别，以及实时操作系统如何确保任务在预定时间内完成。 3. 内核结构：书中深入讨论了µC/OS-II内核的架构，包括任务调度、中断处理和内核服务的实现。 4. 任务管理：这部分内容涵盖了任务创建、删除、优先级设置和任务状态管理等关键操作。 5. 时间管理：详细阐述了系统定时器的使用，包括延时函数、时间基和超时机制。 6. 定时器管理：介绍了如何配置和管理µC/OS-II中的软件定时器，用于执行周期性任务或在特定时间点触发事件。 7. 事件控制块（Event Control Blocks, ECBs）：说明了ECBs如何用于同步和通信，使得任务间可以等待特定事件的发生。 8. 信号量管理：涵盖了二进制信号量和计数信号量的使用，用于资源的共享和保护。 9. 互斥信号量：详细讨论了互斥信号量的实现，确保同一时刻只有一个任务访问临界区。 10. 事件标志管理：事件标志组提供了一种多事件等待机制，允许任务等待多个事件中的一个或多个。 11. 消息邮箱管理：描述了如何通过邮箱发送和接收消息，实现任务间的异步通信。 12. 消息队列管理：详细介绍了消息队列的使用，允许存储和传递固定大小的消息。 13. 内存管理：这部分内容涉及到内存分配和释放，以及如何定制内存池以满足不同内存需求。 14. µC/OS-II移植：手册提供了如何将操作系统移植到新的硬件平台上的指南，包括针对80x86架构的两种移植实例。 15. 编译器运行时库的线程安全：讨论了编译器运行时库如何在多线程环境中确保安全。 16. API参考：包含完整的µC/OS-II API文档，为开发者提供了函数调用和参数的详细信息。 17. 配置手册：介绍了如何根据具体项目需求配置和定制µC/OS-II。 18. PC服务：可能包含了与个人计算机相关的支持和服务信息。 19. 编码约定：提供了代码编写的标准和最佳实践，确保代码的可读性和一致性。 20. 许可政策：详细说明了使用和分发µC/OS-II的许可条款。 21. 快速参考：为开发者提供了快速查找关键信息的便利。 22. TO Utility：可能是某种工具或实用程序的简要介绍。 23. 参考文献：列出了一些参考书籍或文章，供进一步学习和研究。这本用户手册全面覆盖了µC/OS-II的各个方面，无论是初学者还是经验丰富的开发者，都能从中获得宝贵的知识，更好地理解和利用这个嵌入式实时操作系统。

µC/OS-II User's Manual

Figure - Figure 1.2 Initialization of the display by TaskStartDispInit().

(3) TaskStart() then invokes the macro OS_ENTER_CRITICAL() . OS_ENTER_CRITICAL() is

basically a processor-specific macro and its used to disable interrupts (see Chapter 13,

Porting µC/OS-II ).

µC/OS-II, like all kernel, requires a time source to keep track of delays and timeouts. In(4)

real mode, the PC offers such a time source which occurs every 54.925 ms (18.20648

Hz) and is called a . allows us to replace the address where the PC goestick PC_VectSet()

to service the DOS tick with one that will be used by µC/OS-II. However, µC/OS-II will

still call the DOS tick handler every 54.925 ms. This technique is called and ischaining

setup by (see ).PC_DOSSaveReturn() Chapter 18, PC Services

We then change the tick rate rate from 18.2 Hz to 200 Hz. I selected 200 Hz because it’s(5)

almost an exact multiple of 18.2 Hz (i.e. 11 times faster). I never quite understood why

IBM selected 18.2 Hz instead of 20 Hz as the tick rate on the original PC. Instead of

setting up the 82C54 timer to divide the timer input frequency by 59,659 to obtain a nice

20 Hz, it appears that they left the 16-bit timer overflow every 65,536 pulses! Changing

the tick rate is handled by another PC service called and is passed thePC_SetTickRate()

desired tick rate ( is set to 200 in ).OS_TICKS_PER_SEC OS_CPU.H

We then invoke the macro . is basically a(6) OS_EXIT_CRITICAL() OS_EXIT_CRITICAL()

µC/OS-II User's Manual

void Task (void *pdata)

{

INT8U x;

INT8U y;

INT8U err;

for (;;) { (1)

OSSemPend(RandomSem, 0, &err); (2)

x = random(80); (3)

y = random(16); (4)

OSSemPost(RandomSem); (5)

PC_DispChar(x, y + 5, *(char *)pdata, DISP_FGND_LIGHT_GRAY); (6)

OSTimeDly(1); (7)

}

Listing - Listing 1.5 Example #1, TEST.C, Task().

As I previously mentioned, a µC/OS-II task is typically an infinite loop.(1)

The task starts by acquiring the semaphore which guards access to the Borland compiler(2)

random number generator function. This is done by calling and passing itOSSemPend()

the ‘handle’ (see L1.1(6)) of the semaphore which was created to guard access to the

random number generator function. The second argument of is used toOSSemPend()

specify a timeout. A value of 0 means that this task will wait forever for the semaphore.

Because the semaphore was initialized with a count of one and no other task has

requested the semaphore, is allowed to continue execution. If the semaphore wasTask()

‘owned’ by another task, µC/OS-II would have suspended this task, and executed the

next most important task.

The random number generator function is called and a value between 0 and 79(3)

(inclusively) is returned. This happens to be the ‘X’ coordinate where we want to display

the character ‘0’ (for this task) on the screen.

Again, the random number generator is called and returns a number between 0 and 15(4)

(inclusively). This value will be used to determine the ‘Y’ position of the character to

display.

The semaphore is released by calling . Here we simply need to specify the(5) OSSemPost()

semaphore ‘handle’.

We can now display the character that was passed to when was created.(6) Task() Task()

µC/OS-II User's Manual

For the first instance of , the character would be ‘0’ and the last instance, it’s ‘9’. ITask()

added an offset of 5 lines from the top so that I don’t overwrite the header at the top of

the display (see Figure 1.1).

Finally, calls to tell µC/OS-II that it’s done executing and to give(7) Task() OSTimeDly()

other tasks a chance to run. The value of 1 means that I want this task to delay for one

clock tick or, 5 ms since the tick rate is 200 Hz. When is called, µC/OS-IIOSTimeDly()

suspends the calling function and executes the next most important task. In this case, it

would be another instance of which would display ‘1’. This process goes on forTask()

all instances of and thus, that’s why Figure 1.1 looks the way it does.Task()

If you have the Borland C/C++ V4.5x compiler installed in the \ directory, you canC: BC45

experiment with . After modifying , you can type MAKETEST from theTEST.C TEST.C

command line prompt of the TEST directory which builds a new . If you don’t haveTEST.EXE

the Borland C/C++ V4.5x or your have it installed in a different directory, you can make the

appropriate changes to , and .TEST.MAK INCLUDES.H TEST.LNK

The SOURCE directory contains four files: , , and . INCLUDES.H OS_CFG.H TEST.C TEST.LNK

is used to determine µC/OS-II configuration options. is the linker commandOS_CFG.H TEST.LNK

file for the Borland linker, TLINK.

Example 2: Stack Checking

Example #2 demonstrates the stack checking feature of µC/OS-II. The amount of stack space

used by each task is displayed along with the amount of free stack space. Also, Example #2

shows the execution time of the stack checking function since it depends onOSTaskStkChk()

the size of each stack. It turns out that a heavily used stack requires less processing time.

The code for Example #2 is found in the directory. You can\SOFTWARE\uCOS-II\EX2_x86L\BC45

open a DOS window and type:

CD \SOFTWARE\uCOS-II\Ex2_x86L\BC45\TEST

To execute example #2, simply type TEST at the command line prompt. The DOS window

will run the program.TEST.EXE

After about one second, you should see the screen shown in Figure 1.3.

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