Transcript Introduction

MicroC/OS-II : The Real-Time
Kernel
Prof. Sung Jo Kim
School of Computer Science and Engineering
Chung-Ang Univ.
2015-07-08
MicroC/OS-II(Ch1)
1
INTRODUCTION
2015-07-08
MicroC/OS-II(Ch1)
2
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)
2015-07-08
MicroC/OS-II(Ch1)
3
Brief History
new version C/OS-III provides more
features
 The
• 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.
2015-07-08
MicroC/OS-II(Ch1)
4
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
2015-07-08
MicroC/OS-II(Ch1)
5
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/po
rts.html)
2015-07-08
MicroC/OS-II(Ch1)
6

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)
2015-07-08
MicroC/OS-II(Ch1)
7

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)
2015-07-08
MicroC/OS-II(Ch1)
8
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
– typedef
– typedef
– typedef
2015-07-08
unsigned
unsigned
unsigned
unsigned
char
int
short
long
INT8U
INT16U
INT16U (for 32-bit)
INT32U
MicroC/OS-II(Ch1)
9
 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
2015-07-08
MicroC/OS-II(Ch1)
10
 Fully
preemptible real-time, deterministic,
multitasking kernel for microprocessors,
microcontrollers and DSPs
 Multitasking
• Manage up to 64 tasks
– 8 system tasks and 56 application tasks
– Up to 63 app tasks allowed
• No round-robin allowed
– Each task has a unique 64 priority levels
2015-07-08
MicroC/OS-II(Ch1)
11
 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.)
2015-07-08
MicroC/OS-II(Ch1)
12
 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()
2015-07-08
MicroC/OS-II(Ch1)
13
 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
2015-07-08
MicroC/OS-II(Ch1)
14
 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
2015-07-08
MicroC/OS-II(Ch1)
15
 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.
2015-07-08
MicroC/OS-II(Ch1)
16
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
2015-07-08
MicroC/OS-II(Ch1)
17
Chapter 1
Getting Started with C/OS-II
2015-07-08
MicroC/OS-II(Ch1)
18
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)
2015-07-08
MicroC/OS-II(Ch1)
19
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
2015-07-08
MicroC/OS-II(Ch1)
20
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)
2015-07-08
MicroC/OS-II(Ch1)
21
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
2015-07-08
MicroC/OS-II(Ch1)
22
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
2015-07-08
MicroC/OS-II(Ch1)
23
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
2015-07-08
MicroC/OS-II(Ch1)
24
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)
2015-07-08
MicroC/OS-II(Ch1)
25
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
2015-07-08
MicroC/OS-II(Ch1)
26
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
2015-07-08
MicroC/OS-II(Ch1)
27
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
2015-07-08
MicroC/OS-II(Ch1)
28
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
2015-07-08
MicroC/OS-II(Ch1)
29
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
2015-07-08
MicroC/OS-II(Ch1)
30
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
wheel spins clockwise at 5 rotations
per second while Task3()’s 2.5 rotations per
second
 Task2()’s
2015-07-08
MicroC/OS-II(Ch1)
31
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
2015-07-08
MicroC/OS-II(Ch1)
32
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
2015-07-08
MicroC/OS-II(Ch1)
33
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
2015-07-08
MicroC/OS-II(Ch1)
34
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
2015-07-08
MicroC/OS-II(Ch1)
35
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
2015-07-08
MicroC/OS-II(Ch1)
36
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()
2015-07-08
MicroC/OS-II(Ch1)
37
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
2015-07-08
MicroC/OS-II(Ch1)
38
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
2015-07-08
MicroC/OS-II(Ch1)
39
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
2015-07-08
MicroC/OS-II(Ch1)
40