IAR PowerPac RTOS User Guide

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** demo program to illustrate the use of resource semaphores*/OS_STACKPTR int StackMain[100], StackClock[50];OS_TASK TaskMain,TaskClock;OS_SEMA SemaLCD;void TaskClock(void) {char t=-1;char s[] = "00:00";while(1) {while (TimeSec==t) Delay(10);t= TimeSec;s[4] = TimeSec%10+'0';s[3] = TimeSec/10+'0';s[1] = TimeMin%10+'0';s[0] = TimeMin/10+'0';OS_Use(&SemaLCD); /* Make sure nobody else uses LCD */LCD_Write(10,0,s);OS_Unuse(&SemaLCD); /* Release LCD */}}void TaskMain(void) {signed char pos ;LCD_Write(0,0,"Software tools by IAR Systems ! ") ;OS_Delay(2000);while (1) {for ( pos=14 ; pos >=0 ; pos-- ) {OS_Use(&SemaLCD); /* Make sure nobody else uses LCD */LCD_Write(pos,1,"train "); /* Draw train */OS_Unuse(&SemaLCD); /* Release LCD */OS_Delay(500);}OS_Use(&SemaLCD); /* Make sure nobody else uses LCD */LCD_Write(0,1," ") ;OS_Unuse(&SemaLCD); /* Release LCD */}}void InitTask(void) {OS_CREATERSEMA(&SemaLCD); /* Creates resource semaphore */OS_CREATETASK(&TaskMain, 0, Main, 50, StackMain);OS_CREATETASK(&TaskClock, 0, Clock, 100, StackClock);}In most applications, the routines that access a resource should automatically call OS_Use() and OS_Unuse() so thatwhen using the resource you do not have to worry about it and can use it just as you would in a single-task system. Thefollowing is an example of how to implement a resource into the routines that actually access the display:/** Simple example when accessing single line dot matrix LCD*/OS_RSEMA RDisp; /* Define resource semaphore */void UseDisp() { /* Simple routine to be called before using display */OS_Use(&RDisp);}void UnuseDisp() { /* Simple routine to be called after using display */OS_Unuse(&RDisp);}void DispCharAt(char c, char x) {UseDisp();LCDGoto(x, y);LCDWrite1(ASCII2LCD(c));UnuseDisp();}void DISPInit(void) {OS_CREATERSEMA(&RDisp);}50IAR PowerPac RTOSfor ARM CoresPPRTOS-2
Resource semaphoresResource semaphores API function overviewRoutineOS_CREATERSEMA()OS_Use()OS_Unuse()OS_Request()OS_GetSemaValue()OS_GetResourceOwner()OS_DeleteRSema()Table 40: Resource semaphore API overviewOS_CREATERSEMA()DescriptionMacro that creates a resource semaphore.Prototypevoid OS_CREATERSEMA (OS_RSEMA* pRSema);ParameterDescriptionpRSemaTable 41: OS_CREATESEMA() parameter listAdditional InformationAfter creation, the resource is not blocked; the value of the counter is 0.OS_Use()DescriptionClaims a resource and blocks it for other tasks.Prototypeint OS_Use (OS_RSEMA* pRSema);ParameterDescriptionpRSemaTable 42: OS_Use() parameter listReturn valueThe counter value of the semaphore.A value larger than 1 means the resource was already locked by the calling task.Additional InformationDescriptionMacro that creates a resource semaphore.Claims a resource and blocks it for other tasks.Releases a semaphore currently in use by a task.Requests a specified semaphore, blocks it for other tasks if it is available. Continuesexecution in any case.Returns the value of the usage counter of a specified resource semaphore.Returns a pointer to the task that is currently using (blocking) a resource.Deletes a specified resource semaphore.Pointer to the data structure for a resource semaphore.Pointer to the data structure for a resource semaphore.The following situations are possible:● Case A: The resource is not in use.If the resource is not used by a task, which means the counter of the semaphore is 0, the resource will be blockedfor other tasks by incrementing the counter and writing a unique code for the task that uses it into the semahore.● Case B: The resource is used by this task.The counter of the semaphore is simply incremented. The program continues without a break.● Case C: The resource is being used by another task.The execution of this task is suspended until the resource semaphore is released. In the meantime if the taskblocked by the resource semaphore has a higher priority than the task blocking the semaphore, the blocking task isassigned the priority of the task requesting the resource semaphore. This is called priority inversion. Priorityinversion can only temporarily increase the priority of a task, never reduce it.PPRTOS-251
Page 1 and 2: IAR PowerPac RTOSUser GuidePPRTOS-2
Page 3 and 4: PrefaceWelcome to the IAR PowerPac
Page 5 and 6: ContentsPreface ...................
Page 7 and 8: ContentsOS_WaitCSema() ............
Page 9 and 10: ContentsOS_LeaveInterrupt() .......
Page 11 and 12: Introduction to IAR PowerPacRTOSWha
Page 13 and 14: Basic conceptsTasksIn this context,
Page 15 and 16: Basic conceptsPREEMPTIVES MULTITASK
Page 17 and 18: Basic conceptsMAILBOXES AND QUEUESA
Page 19 and 20: Basic conceptsThe active task may b
Page 21 and 22: Basic conceptsThe flowchart below i
Page 23 and 24: Basic conceptsLIST OF LIBRARIESIn y
Page 25 and 26: Task routinesIntroductionA task tha
Page 27 and 28: Task routinesOS_CREATETASK() can be
Page 29 and 30: Task routinesExampleThe following e
Page 31 and 32: Task routinesExampleint sec,min;voi
Page 33 and 34: Task routinesAdditional Information
Page 35 and 36: Task routinesReturn valueOS_TASKID:
Page 37 and 38: Software timersSoftware timerA soft
Page 39 and 40: Software timers#define OS_CREATETIM
Page 41 and 42: Software timersOS_SetTimerPeriod()D
Page 43 and 44: Software timersAdditional Informati
Page 45 and 46: Software timersAdditional Informati
Page 47 and 48: Software timersExampleOS_TIMER TIME
Page 49: Resource semaphoresIntroductionReso
Page 53 and 54: Resource semaphoresOS_Request()Desc
Page 55 and 56: Counting SemaphoresIntroductionCoun
Page 57 and 58: Counting SemaphoresPrototypevoid OS
Page 59 and 60: Counting SemaphoresReturn value0: I
Page 61 and 62: MailboxesWhy mailboxes?In the prece
Page 63 and 64: MailboxesMailboxes API function ove
Page 65 and 66: MailboxesExampleSingle-byte mailbox
Page 67 and 68: MailboxesPrototypevoid OS_GetMail (
Page 69 and 70: MailboxesOS_WaitMail()DescriptionWa
Page 71 and 72: QueuesWhy queues?In the preceding c
Page 73 and 74: QueuesReturn valueThe size of the r
Page 75 and 76: QueuesExamplestatic void MemoryTask
Page 77 and 78: Task eventsIntroductionTask events
Page 79 and 80: Task eventsExampleOS_WaitEventTimed
Page 81 and 82: Task eventsPrototypechar OS_ClearEv
Page 83 and 84: Event objectsIntroductionEvent obje
Page 85 and 86: Event objectsExampleif (OS_EVENT_Wa
Page 87 and 88: Event objectsExampleOS_EVENT_Reset(
Page 89 and 90: Heap type memory managementANSI C o
Page 91 and 92: Fixed block size memory poolsIntrod
Page 93 and 94: Fixed block size memory poolsProtot
Page 95 and 96: Fixed block size memory poolsProtot
Page 97 and 98: StacksIntroductionThe stack is the
Page 99 and 100: InterruptsIntroductionIn this chapt
Page 101 and 102:
InterruptsRules for interrupt handl
Page 103 and 104:
InterruptsOS_LeaveInterruptNoSwitch
Page 105 and 106:
InterruptsNesting interrupt routine
Page 107 and 108:
Critical RegionsIntroductionCritica
Page 109 and 110:
System variablesIntroductionThe sys
Page 111 and 112:
Configuration for your targetsystem
Page 113 and 114:
Time measurementIntroductionIAR Pow
Page 115 and 116:
Time measurementPrototypeU32 OS_Get
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Time measurementPrototypeOS_U32 OS_
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RTOS-aware debuggingThis chapter de
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RTOS-aware debuggingTimersA softwar
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DebuggingRuntime errorsSome error c
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DebuggingValue Define Description17
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Performance and resource usageThis
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Performance and resource usageThe c
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Performance and resource usage*/sta
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ReentranceAll routines that can be
Page 135 and 136:
LimitationsThe following limitation
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Source code of kernel and libraryIn
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Additional modulesKeyboard manager:
Page 141 and 142:
FAQ (frequently asked questions)Q:
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GlossaryActive TaskCooperativemulti
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IndexIndexAAdditional modules . . .
Page 147:
IndexOS_WaitSingleEventTimed(). . .
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IAR PowerPac RTOS User Guide

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