程序清单 L 1.8建立其它任务的任务。
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void TaskStart (void *data)
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{
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Prevent compiler warning by assigning ‘data’ to itself;
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Display banner identifying this as EXAMPLE #1; (1)
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OS_ENTER_CRITICAL();
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PC_VectSet(0x08, OSTickISR); (2)
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PC_SetTickRate(200); (3)
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OS_EXIT_CRITICAL();
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Initialize the statistic task by calling ‘OSStatInit()’; (4)
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Create 10 identical tasks; (5)
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for (;;) {
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Display the number of tasks created;
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Display the % of CPU used;
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Display the number of task switches in 1 second;
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Display uC/OS-II’s version number
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If (key was pressed) {
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if (key pressed was the ESCAPE key) {
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PC_DOSReturn();
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}
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}
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Delay for 1 Second;
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}
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}
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在建立其他任务之前，必须调用OSStatInit()[L1.8(4)]来确定用户的PC有多快，如程序清单L1.9所示。在一开始，OSStatInit()就将自身延时了两个时钟节拍，这样它就可以与时钟节拍中断同步[L1.9(1)]。因此，OSStatInit()必须在时钟节拍启动之后调用；否则，用户的应用程序就会崩溃。当uC/OS-II调用OSStatInit()时，一个32位的计数器OSIdleCtr被清为0 [L1.9(2)]，并产生另一个延时，这个延时使OSStatInit()挂起。此时，uCOS-II没有别的任务可以执行，它只能执行空闲任务（uC/OS-II的内部任务）。空闲任务是一个无线的循环，它不断的递增OSIdleCtr[L1.9(3)]。1秒以后，uCOS-II重新开始OSStatInit()，并且将OSIdleCtr保存在OSIdleMax中[L1.9(4)。所以OSIdleMax是OSIdleCtr所能达到的最大值。而当用户再增加其他应用代码时，空闲任务就不会占用那样多的CPU时间。OSIdleCtr不可能达到那样多的记数，（如果拥护程序每秒复位一次OSIdleCtr）CPU利用率的计算由uC/OS-II 中的OSStatTask()函数来完成，这个任务每秒执行一次。而当OSStatRdy置为TRUE[L1.9(5)],表示uC/OS-II将统计CPU的利用率。程序清单 L 1.12TaskStart()的伪码。.
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void TaskStart (void *data)
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{
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Prevent compiler warning by assigning ‘data’ to itself;
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Display a banner and non-changing text;
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Install uC/OS-II’s tick handler;
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Change the tick rate to 200 Hz;
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Initialize the statistics task;
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Create 2 mailboxes which are used by Task #4 and #5; (1)
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Create a task that will display the date and time on the screen; (2)
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Create 5 application tasks;
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for (;;) {
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Display #tasks running;
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Display CPU usage in %;
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Display #context switches per seconds;
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Clear the context switch counter;
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Display uC/OS-II’s version;
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If (Key was pressed) {
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if (Key pressed was the ESCAPE key) {
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Return to DOS;
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}
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}
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Delay for 1 second;
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}
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}
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程序清单 L 1.13例2, 任务1
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void Task1 (void *pdata)
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{
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INT8U err;
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OS_STK_DATA data;
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INT16U time;
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INT8U i;
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char s[80];
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pdata = pdata;
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for (;;) {
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for (i = 0; i < 7; i++) {
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PC_ElapsedStart(); (1)
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err = OSTaskStkChk(TASK_START_PRIO+i, &data)
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time = PC_ElapsedStop(); (2)
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if (err == OS_NO_ERR) {
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sprintf(s, "%3ld %3ld %3ld %5d",
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data.OSFree + data.OSUsed,
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data.OSFree,
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data.OSUsed,
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time);
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PC_DispStr(19, 12+i, s, DISP_FGND_YELLOW);
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}
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}
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OSTimeDlyHMSM(0, 0, 0, 100); (3)
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}
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}
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程序清单L1.14所示的任务2在屏幕上显示一个顺时针旋转的指针（用横线，斜线等字符表示—译者注），每200ms旋转一格。程序清单 L 1.14任务2
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void Task2 (void *data)
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{
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data = data;
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for (;;) {
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PC_DispChar(70, 15, '|', DISP_FGND_WHITE + DISP_BGND_RED);
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OSTimeDly(10);
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PC_DispChar(70, 15, '/', DISP_FGND_WHITE + DISP_BGND_RED);
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OSTimeDly(10);
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PC_DispChar(70, 15, '-', DISP_FGND_WHITE + DISP_BGND_RED);
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OSTimeDly(10);
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PC_DispChar(70, 15, '\\', DISP_FGND_WHITE + DISP_BGND_RED);
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OSTimeDly(10);
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}
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}
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任务3(程序清单 L1.15)也显示了与任务2相同的一个旋转指针，但是旋转的方向不同。任务3在堆栈中分配了一个很大的数组，将堆栈填充掉，使得OSTaskStkChk()只需花费很少的时间来确定堆栈的利用率，尤其是当堆栈已经快满的时候。程序清单 L 1.15任务3
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void Task3 (void *data)
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{
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char dummy[500];
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INT16U i;
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data = data;
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for (I = 0; i < 499; i++) {
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dummy = '?';
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}
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for (;;) {
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PC_DispChar(70, 16, '|', DISP_FGND_WHITE + DISP_BGND_BLUE);
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OSTimeDly(20);
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PC_DispChar(70, 16, '\\', DISP_FGND_WHITE + DISP_BGND_BLUE);
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OSTimeDly(20);
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PC_DispChar(70, 16, '-', DISP_FGND_WHITE + DISP_BGND_BLUE);
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OSTimeDly(20);
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PC_DispChar(70, 16, '/', DISP_FGND_WHITE + DISP_BGND_BLUE);
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OSTimeDly(20);
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}
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}
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任务4(程序清单L1.16)向任务5发送消息并等待确认[程序清单L1.16(1)]。发送的消息是一个指向字符的指针。每当任务4从任务5收到确认[程序清单L1.16(2)],就将传递的ASCII码加1再发送[程序清单L1.16(3)]，结果是不断的传送“ABCDEFG....”。程序清单 L 1.28用户定义的OSTaskStatHook().
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void OSTaskStatHook (void)
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{
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char s[80];
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INT8U i;
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INT32U total;
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INT8U pct;
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total = 0L;
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for (I = 0; i < 7; i++) {
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total += TaskUserData.TaskTotExecTime; (1)
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DispTaskStat(i); (2)
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}
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if (total > 0) {
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for (i = 0; i < 7; i++) {
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pct = 100 * TaskUserData.TaskTotExecTime / total; (3)
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sprintf(s, "%3d %%", pct);
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PC_DispStr(62, i + 11, s, DISP_FGND_YELLOW); (4)
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}
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}
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if (total > 1000000000L) {
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for (i = 0; i < 7; i++) {
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TaskUserData.TaskTotExecTime = 0L;
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}
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}
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}
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