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MicroC/OS-II : The Real-Time Kernel Prof. Sung Jo Kim School of Computer Science and Engineering

MicroC/OS-II : The Real-Time Kernel Prof. Sung Jo Kim School of Computer Science and Engineering Chung-Ang Univ. INTRODUCTION. Brief History. Developed in C by Jean Labrosse in 1992 Currently, maintained by Micrium Inc. ( http://www.micrium.com/products/rtos/kernel/rtos.html )

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MicroC/OS-II : The Real-Time Kernel Prof. Sung Jo Kim School of Computer Science and Engineering

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  1. MicroC/OS-II: The Real-Time Kernel Prof. Sung Jo Kim School of Computer Science and Engineering Chung-Ang Univ. MicroC/OS-II(Ch1)

  2. INTRODUCTION MicroC/OS-II(Ch1)

  3. Brief History • Developed in C by Jean Labrosse in 1992 • Currently, maintained by Micrium Inc. (http://www.micrium.com/products/rtos/kernel/rtos.html) • The current version is C/OS-II v3.10(v2.52 for textbook) MicroC/OS-II(Ch1)

  4. Brief History • The new version C/OS-III provides more features • Round-robin scheduling • Allow multiple tasks to run at the same priority level • Near zero interrupt disable time • Unlimited number of application tasks • Error checking and more.  MicroC/OS-II(Ch1)

  5. Brief History • Licensing • Free distribution of  C/OS-II source and object code to accredited Colleges and Universities w/o requiring license • ‘Object Code Distribution License’ is required for commercial products MicroC/OS-II(Ch1)

  6. Brief History •  C/OS-II • A highly portable, ROMable, scalable, preemptive, real-time, deterministic multitasking kernel for microprocessors, microcontrollers and DSP-based devices • Actual target: embedded system • Easily portable to many processor (http://www.micrium.com/products/rtos/kernel/ports.html) MicroC/OS-II(Ch1)

  7. Major available ports • ACTEL (Cortex-M1) • ALTERA (NIOS II) • Analog Devices (ADSP-21xx) • ARM by various 3rd-party (Samsung, TI, PHILIPS, etc.) • ATMEL (SAM7, SAM9) • Energy Micro (Cortex-M4F) • Freescale (9S08) • Fujitsu (FR-50, SPARClite) • Infineon (TriCore, 80C16x) • Intel (80x86) • Lattice(Mico32) MicroC/OS-II(Ch1)

  8. Major available ports • LUMINARY Micro (Cortex-M3) • Microchip (PIC24) • MIPS Technologies (M14K) • NXP (ARM7, ARM9) • Renesas (H8) • SAMSUNG (ARM7, ARM0) • ST (STR7, STR9) • TI (MSP-430, TMS320) • Toshiba (Cortex-M3) • XILINX (MicroBlaze) • Zilog (eZ80, Z-80 and Z-180) MicroC/OS-II(Ch1)

  9. C/OS-II Features • Open source code • Portable • Written in ANSI C + target-specific code written in assembly language • Run on most 8-, 16-, 32- or 64-bit platforms • Portable data types • typedef unsigned char INT8U • typedef unsigned int INT16U • typedef unsigned short INT16U (for 32-bit) • typedef unsigned long INT32U MicroC/OS-II(Ch1)

  10. ROMable • Designed for embedded applications • Embedded as part of products • Scalability using conditional compilation • May contain only needed features for a small footprint • Depending on the processor, the size can be reduced as small as between 5KB to 24KB MicroC/OS-II(Ch1)

  11. Fully preemptible real-time, deterministic, multitasking kernel for microprocessors, microcontrollers and DSPs • Multitasking • Manage up to 64 tasks • 8 system tasksand 56 application tasks • Up to 63 app tasks allowed • No round-robin allowed • Each task has a unique 64 priority levels MicroC/OS-II(Ch1)

  12. Deterministic • The execution time for most of the functions and services is both constant and known in advance • The execution time is independent of the number of tasks currently running • Exception • OSTimeTick() • Some event flag services(e.g., OSFlagCreate(), OSFlagPost(), etc.) MicroC/OS-II(Ch1)

  13. Task stacks • Each tasks requires its own stack • Different stack sizes for different tasks • Exact size can be determined by stack-checking feature • Reduce the amount of RAM needed by an each application code • Use OSTaskStkChk() MicroC/OS-II(Ch1)

  14. System services • Semaphores • Mutual Exclusion Semaphores (to reduce priority inversions) • Event Flags • Message Mailboxes • Message Queues • Task Management (Create, Delete, Change Priority, Suspend/Resume etc.) • Fixed Sized Memory Block Management • Time Management • Timer Management MicroC/OS-II(Ch1)

  15. Interrupt management: 255 levels • Robust and Reliable • Used in 100s of commercial apps since 1992 • Suitable for Safety Critical Systems common to Aviation and Medical products • Certifiable for use in Safety Critical Systems • A Validation Suite provides all of the documentation necessary to deliver µC/OS-II as a pre-certifiable software component for safety critical systems • Include avionics RTCA DO-178B and EUROCAE/ ED-12B, medical FDA 510(k), and IEC 61508 standard for transportation and nuclear systems MicroC/OS-II(Ch1)

  16. Robust and Reliable • Revised to follow most of the 127 MISRA C rules • The source code for µC/OS-II is now 99% compliant with the Motor Industry Software Reliability Association (MISRA) C Coding Standards. • Improve the safety, reliability and predictability of C programs in critical automotive systems. • Members of the MISRA consortium : Delco Electronics, Ford Motor Company, Jaguar Cars Ltd., Lotus Engineering, Lucas Electronics, Rolls-Royce, Rover Group Ltd., etc. MicroC/OS-II(Ch1)

  17. Applications • Avionics • Medical equipment/devices • Data communications equipment • White goods (Appliances) • Mobile phones, PDAs, MIDs • Industrial controls • Consumer electronics • Automotive • A wide range of embedded applications MicroC/OS-II(Ch1)

  18. Chapter 1 Getting Started with C/OS-II MicroC/OS-II(Ch1)

  19. Installing C/OS-II • The installation environments • Compiler: the Borland Turbo C++ 4.5 • SW platform: Win95/98/Me/NT/2000/XP computer • Example #1: Basic multitasking • Each of 10 tasks displays a specific number at arbitrary locations on the screen • #Tasks: 13 • 2 internal tasks: • The idle task (OS_TaskIdle)(): Executed when all tasks are waiting either for events or for time to expire • A task for CPU usage statistics • Other 11 tasks are created (Listing1.1 on pp3) MicroC/OS-II(Ch1)

  20. Installing C/OS-II • Listing 1.2: main() • OsInit() • Invoked before any other services • Create two tasks • An idle task: Execute when no other task is ready to run • A statistic task: Compute CPU usage • PC_DOSSaveReturn() • Save the processors’s registers for proper return to DOS • Must be called before setting C/OS-II context-switch vector • PC_VectSet(uCos, OSCtxSw) • Install the C/OS-II context-switch handler • uCos: The interrupt vector # (0 ~ 255) • OSCtxSw: The address of the interrupt/exception handler MicroC/OS-II(Ch1)

  21. Installing C/OS-II • Listing 1.2 • OSSemCreate(INT16U cnt) • Create a binary semaphore to protect the random-number generator function • Return a handle to the semaphore used for its reference • OSStart() • Start multitasking and give control to C/OS-II • At least one task should be created before being called • Listing 1.3: TaskStart() • pdata = pdata just for fake reference to avoid compiler warning • TaskStartDispInit() • Make 25 consecutive calls to PC_DispStr(x,y,s,color) to display an ASCII string s in color from (x,y) MicroC/OS-II(Ch1)

  22. Installing C/OS-II • Listing 1.3: TaskStart() • PC_VectSet(0x08, OSTickISP): Replace the address of the DOS tick service with one used by C/OS-II • PC-SetTickRate(OS_TICKS_PER_SEC): Change the tick rate to 200 rather than 18.2Hz • OSStatInit(): Determine the speed of CPU to find out the actual usage of the CPU • TaskStartCreateTasks(): Create N_TASKS identical tasks MicroC/OS-II(Ch1)

  23. Installing C/OS-II • Listing 1.3: TaskStart() • TaskStartDisp(): Display various information at the bottom of the DOS window • PC_GetKey(): Check if a key is pressed • OSTimeDlyHMSM(0, 0, 1, 0): Suspend the current task for 1 sec. to initiate next most important task MicroC/OS-II(Ch1)

  24. Installing C/OS-II • Listing 1.4: TaskStartCreateTasks() • OSTaskCreate(Task, (void *) &TaskData[i],&TaskStk[i][TASK_STK_SIZE-1], i+1) • Task() places an ASCII character at a random location • Create tasks with priorities 1 through 10 MicroC/OS-II(Ch1)

  25. Installing C/OS-II • Listing 1.5: Task() • OSSemPend(RandomSem, 0, &err) • Acquire the semaphore to guard access to random# generator • Timeout: The value of 0 means no timeout • OSTimeDly(1) • Notify C/OS-II that it’s done • Delay the current task for 1 clock tick (5ms) MicroC/OS-II(Ch1)

  26. Installing C/OS-II • Example #2 shows • The amount of stack space used by each task • The amount of free stack space • The execution time of the stack-checking function • Useful when we don’t know • How much stack space needs to be allocated for each task • How much execution time it takes to determine each task stack size MicroC/OS-II(Ch1)

  27. Installing C/OS-II • Listing 1.7: main() • PC_ElapsedInit() • Initialize the elapsed-time-measurement function • Measure the execution time of PC_ElapsedStart() and PC_ElapsedStop() • OSTaskStkInit_FPE_x86(&pptos,&ppbos,&psize) • Modify the top-of-stack pointer • Called prior to calling OSTaskCreateExt() • Initialize the stack frame of each task for ft-pt operations for Borland v3.x and 4.5x compilers MicroC/OS-II(Ch1)

  28. Installing C/OS-II • Listing 1.7: main() • OSTaskCreateExt(): Also, modify the stack and check the stack size at run time • Pass the new TOS pointer modified by OSTaskStkInit_FPE_x86() • Pass a task ID, which can be any value • Pass the new size modified by OSTaskStkInit_FPE_x86() • Pass the new TOS pointer modified by OSTaskStkInit_FPE_x86() • Pass a TCB extension pointer • A set of options necessary for stack-size checking and stack clearing MicroC/OS-II(Ch1)

  29. Installing C/OS-II • Listing 1.8: TaskStart() • TaskStartDispInit() initializes the display • OSMboxCreate(void *msg) • Create and initialize a mailbox • Empty when msg is NULL • Allow tasks and ISRs to send a pointer-sized variable to one or more tasks • TaskStartCreateTasks() • Create 6 tasks using OSTaskCreateExt() • OSTimeDly(OS_TICKS_SEC) • Delay TaskSart() for OS_TICKS_SEC ticks MicroC/OS-II(Ch1)

  30. Installing C/OS-II • Listing 1.9: Task1() • Check the size of the stack for each of 7 application tasks • 6 tasks created by TaskStart() and TaskStart() itself • PC_ElapsedStop() returns the time difference in sec • OSTaskStkChk() • Determine the actual stack usage of a task • Two arguments • The task priority of the task to check • A pointer to a data structure to hold task’s stack information MicroC/OS-II(Ch1)

  31. Installing C/OS-II • PC_DispStr(x, y, *s, color) • x and y: Specify the coordinates (col, row) where the 1st char appears • s: A pointer to the array of chars to display • color: Specify the color combination of the chars to be displayed • Task2()’s wheel spins clockwise at 5 rotations per second while Task3()’s 2.5 rotations per second MicroC/OS-II(Ch1)

  32. Installing C/OS-II • Listing 1.11 • OSMboxPost(pevent, msg) • pevent: a pointer to the mailbox • msg: the actual message sent to the task • OSMBoxPend(AckMbox, 0, &err) • Task4() waits for an Ack from Task5 • The 2nd argument specifies a timeout as an integral number of clock ticks MicroC/OS-II(Ch1)

  33. Installing C/OS-II • Example #3 uses (Fig. 1.5) • The TCB extension capability • The user-defined context-switch hook • The user-defined statistic-task hook • Message queues • Listing 1.13 • TASK_USER_DATA holds additional information about a task • Task name • The number of times that a task has executed • Task execution time • Total task execution time • OS_EVENT (Listing 6.1 on pp154): Maintain the state of an ECB MicroC/OS-II(Ch1)

  34. Installing C/OS-II • Listing 1.15, TaskStart() • OSQCreate(start, size) creates a message queue • start: the base address of the message storage area • Size: the number of entries of the message storage area • Returned value: a pointer to the ECB allocated to the queue • TaskStartCreateTasks() • Create six tasks • Each task is assigned an entry in the TaskUserData[] array MicroC/OS-II(Ch1)

  35. Installing C/OS-II • Listing 1.16, Task1() ~ Task4() • OSQPend((*pevent, timeout, *err) • pevent: a pointer to the queue from which the messages are received • Timeout • Maximum timeout = 65535 • Wait forever if timeout = 0 • Returned value: a message sent by a task or an ISR MicroC/OS-II(Ch1)

  36. Installing C/OS-II • Listing 1.17, C/OS-II’s hooks • If OS_CPU_HOOKS_EN = 0, we can declare the hook function in a different file • Listing 1.18, empty hook functions • Listing 1.19, OSTaskSwHook() • Called when C/OS-II switches from a low priority to a higher priority task • PC_ElapsedStop() return the execution time of the task being switched out MicroC/OS-II(Ch1)

  37. Installing C/OS-II • Task control block(OS_TCB) (pp81) • Maintain the task state when being preempted • OSTCBCur points to the TCB of the current task • OSTCBExtPtr • A pointer to a user-definable TCB extension • Only used by OSTaskCreateExt() MicroC/OS-II(Ch1)

  38. Installing C/OS-II • Listing 1.20, OSTaskStatHook() • Called every second from the ststistics task OSTaskStat() • DispTaskStat(i) • Display individual statistics on the screen • Display each task name MicroC/OS-II(Ch1)

  39. Installing C/OS-II • Example #4 • A port is some processor-specific code • Create 10 identical tasks, each running 200 times per second • Each task computes the sine and cosine of an angle • The angle is offset by 36 degrees • Every time the task executes, the angle is incremented by 0.01 MicroC/OS-II(Ch1)

  40. Installing C/OS-II • Listing 1.21, TaskStartCreateTasks() • (void *)&TaskData[i] • An argument passed to a task when it is first started • OS_TASK_OPT_SAVE_FP • Save floating-point registers during a context switch • Listing 1.22, Task() • OSTimeDly(1) • Each task is delayed by 1 tick(50ms) • Each task executes 200 times per second MicroC/OS-II(Ch1)

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