Notes/Warnings

The execution time of OSTimeTick() is directly proportional to the number of tasks created in an application. OSTimeTick() can be called by either an ISR or a task. If called by a task, the task priority should be VERY high (i.e. have a low priority number) because this function is responsible for updating delays and timeouts.

OSVersion()

INT16U OSVersion(void);

OSVersion() is used to obtain the current version of µC/OS-II.

Arguments

NONE

Returned Value

The version is returned as x.yy multiplied by 100. In other words, version 1.00 is returned as 100.

Notes/Warnings

NONE

Example

void TaskX(void *pdata)

{

INT16U os_version;

for (;;) {

.

.

os_version = OSVersion(); /* Obtain uC/OS-II's version */

.

.

}

}

OS_ENTER_CRITICAL()

OS_EXIT_CRITICAL()

OS_ENTER_CRITICAL() and OS_EXIT_CRITICAL() are macros which are used to disable and enable the processor's interrupts, respectively.

Arguments

NONE

Returned Value

NONE

Notes/Warnings

These macros must be used in pair.

Example

INT32U Val;

void TaskX(void *pdata)

{

for (;;) {

.

.

}

}

Chapter 12

Configuration Manual

This chapter provides a description of the configurable elements of µC/OS-II. Because µC/OS-II is provided in source form, configuration of µC/OS-II is done through a number of #define constants. The #define constants are found in a file called OS_CFG.H and should exist for each project/product that you make.

This section describes each of the #define constant in the order in which they are found in OS_CFG.H. Table 12-1 provides a summary of these constants and which µC/OS-II functions they affect.

Of course, OS_CFG.H must be included when µC/OS-II is built in order for the desired configuration to take effect.

Table 12-1a

Table 12-1b

OS_MAX_EVENTS

OS_MAX_EVENTS specifies the maximum number of event control blocks that will be allocated. An event

control block is needed for every message mailbox, message queue or semaphore object. For example, if you have 10 mailboxes, 5 queues and 3 semaphores, you must set OS_MAX_EVENTS to at least 18. If you intend to use either mailboxes, queues and/or semaphores then you MUST set OS_MAX_EVENTS to at least 2.

OS_MAX_MEM_PART

OS_MAX_MEM_PART specifies the maximum number of memory partitions that will be managed by the memory partition manager found in OS_MEM.C. To use memory partition, however, you will also need to set OS_MEM_EN to 1. If you intend to use memory partitions then you MUST set

to at least 2.

OS_MAX_QS

OS_MAX_QS specifies the maximum number of message queues that your application will create. To use message queue services, you will also need to set OS_Q_EN to 1. If you intend to use message queues then you MUST set to at least 2.

OS_MAX_TASKS

OS_MAX_TASKS specifies the maximum number of application tasks that can exist in your application. Note that OS_MAX_TASKS cannot be greater than 62 because µC/OS-II reserves two tasks for itself (see OS_N_SYS_TASKS in uCOS_II.H). If you set OS_MAX_TASKS to the exact number of tasks in your system, you will need to make sure that you revise this value when you add additional tasks. Conversely, if you make OS_MAX_TASKS much higher than your current task requirements (for future expansion), you will be wasting valuable RAM.

OS_LOWEST_PRIO

OS_LOWEST_PRIO specifies the lowest task priority (i.e. highest number) that you intend to use in your application and is provided to allow you to reduce the amount of RAM needed by µC/OS-II. Remember that µC/OS-II’s priorities can go from 0 (highest priority) to a maximum of 63 (lowest possible priority). Setting OS_LOWEST_PRIO to a value less than 63 means that your application cannot create tasks with a priority number higher than OS_LOWEST_PRIO. In fact, µC/OS-II reserves priorities

OS_LOWEST_PRIO and OS_LOWEST_PRIO – 1 for itself. Task of priority

OS_LOWEST_PRIO is reserved for the idle task (OSTaskIdle()) while priority OS_LOWEST_PRIO – 1 is reserved for the statistic task (OSTaskStat()). The priorities of your application tasks can thus take a value between 0 andOS_LOWEST_PRIO – 2 (inclusively). The lowest task priority specified by OS_LOWEST_PRIO is independent of OS_MAX_TASKS. For example, you can setOS_MAX_TASKS to 10 and OS_LOWEST_PRIO to 32. You can thus have up

to 10 application tasks and each of those can have a task priority value between 0 and 30 (inclusively). Note that each task must still have a different priority value. You MUST always set OS_LOWEST_PRIO to a

higher value than the number of application tasks in your system. For example, if you set OS_MAX_TASKS to 20 andOS_LOWEST_PRIO to 10 then you will not be able to create more than

8 application tasks (0…7). You will simply be wasting RAM.

OS_TASK_IDLE_STK_SIZE

OS_TASK_IDLE_STK_SIZE specifies the size of µC/OS-II's idle task. The size is specified not in bytes but in number of elements. This is because a stack MUST be declared to be of type OS_STK. The size of the idle task stack depends on the processor you are using and the deepest anticipated interrupt nesting level. Very little is being done in the idle task but, you should accommodate for at least enough space to store all processor registers on the stack.

OS_TASK_STAT_EN

OS_TASK_STAT_EN specifies whether or not you will enable µC/OS-II's statistics task as well as its

initialization function. When set to 1, the statistic task and the statistic task initialization function are enabled. The statistic task (OSTaskStat()) is used to compute the CPU usage of your application. When enabled, OSTaskStat() executes every second and computes the 8-bit variable OSCPUUsage which provides the percentage of CPU utilization of your application. OSTaskStat() calls OSTaskStatHook() every time it executes so that you can add your own statistics as needed. See OS_CORE.C for details on the statistics task. The priority of OSTaskStat() is always set to

OS_LOWEST_PRIO - 1.

The global variablesOSCPUUsage, OSIdleCtrMax, OSIdleCtrRun and OSStatRdy

will not be declared when OS_TASK_STAT_EN is set to 0. This allows you to reduce the amount of RAM needed by µC/OS-II if you don’t intend to use the statistic task.

OS_TASK_STAT_STK_SIZE

OS_TASK_STAT_STK_SIZE specifies the size of µC/OS-II's statistics task stack. The size is specified not in bytes but in number of elements. This is because a stack is declared as being of type OS_STK. The size of the statistics task stack depends on the processor you are using and the maximum of the following actions:

1.The stack growth associated with performing 32-bit arithmetic

2.The stack growth associated with calling OSTimeDly()

3.The stack growth associated with calling OSTaskStatHook()

4.The deepest anticipated interrupt nesting level

If you want to run stack checking on this task and determine this task’s actual stack requirements then, you must enable code generation for OSTaskCreateExt() by setting OS_TASK_CREATE_EXT_EN to 1. Again, the priority of OSTaskStat() is always set to OS_LOWEST_PRIO - 1.

OS_CPU_HOOKS_EN

This configuration constant indicates whether OS_CPU_C.C declares the hook functions (when set to 1) or not (when set to 0). Recall that µC/OS-II expects the presence of six functions that can either be defined in the port (i.e. in OS_CPU_C.C) or by the application code. These functions are:

1.OSTaskCreateHook()

2.OSTaskDelHook()

3.OSTaskStatHook()

4.OSTaskSwHook()

5.OSTimeTickHook()

OS_MBOX_EN

This constant allows you to enable (when set to 1) or disable (when set to 0) code generation of message mailbox services and data structures. This allows you to reduce the amount of code space when your application does not require the use of message mailboxes.

OS_MEM_EN

This constant allows you to enable (when set to 1) or disable (when set to 0) code generation of µC/OS-II’s partition memory manager and its associated data structures. This allows you to reduce the amount of code and data space when your application does not require the use of memory partitions.

OS_Q_EN

This constant allows you to enable (when set to 1) or disable (when set to 0) code generation of µC/OS-II’s message queue manager and its associated data structures. This allows you to reduce the amount of code and data space when your application does not require the use of message queues. Note that if OS_Q_EN is set to 0 then the #define constant OS_MAX_QS is irrelevant.

OS_SEM_EN

This constant allows you to enable (when set to 1) or disable (when set to 0) code generation of µC/OS-II’s semaphore manager and its associated data structures. This allows you to reduce the amount of code and data space when your application does not require the use of semaphores.

OS_TASK_CHANGE_PRIO_EN

This constant allows you to enable (when set to 1) or disable (when set to 0) code generation of the function OSTaskChangePrio(). If your application never changes task priorities once they are assigned

then you can reduce the amount of code space used by µC/OS-II by setting

OS_TASK_CHANGE_PRIO_EN to 0.

OS_TASK_CREATE_EN

This constant allows you to enable (when set to 1) or disable (when set to 0) code generation for the OSTaskCreate()function. Enabling this function makes µC/OS-II backward compatible with µC/OS’s task creation function. If your application always uses OSTaskCreateExt()

(recommended) then you can reduce the amount of code space used by µC/OS-II by setting OS_TASK_CREATE_EN to 0. Note that you MUST set at least one of the two #defines

OS_TASK_CREATE_EN or OS_TASK_CREATE_EXT_EN to 1. If you wish, you can actually

use both.

OS_TASK_CREATE_EXT_EN

This constant allows you to enable (when set to 1) or disable (when set to 0) code generation of the function OSTaskCreateExt() which is the extended, and more powerful version of the two task creation functions. If your application never uses OSTaskCreateExt() then you can reduce the amount of code space used by µC/OS-II’s by setting OS_TASK_CREATE_EXT_EN to 0. Note, however, that you need the extended task create function to use the stack checking function OSTaskStkChk().

OS_TASK_DEL_EN

This constant allows you to enable (when set to 1) or disable (when set to 0) code generation of the function OSTaskDel() which allows you to delete tasks. If your application never uses this function then you can reduce the amount of code space used by µC/OS-II by setting OS_TASK_DEL_EN to 0.

OS_TASK_SUSPEND_EN

This constant allows you to enable (when set to 1) or disable (when set to 0) code generation of the two functions OSTaskSuspend() and OSTaskResume() which allows you to explicitly suspend and resume tasks, respectively. If your application never uses these functions then you can reduce the amount of code space used by µC/OS-II by setting OS_TASK_SUSPEND_EN to 0.

OS_TICKS_PER_SEC

This constant specifies the rate at which you will call OSTimeTick(). It is up to your initialization code to ensure thatOSTimeTick() is invoked at this rate. This constant is used by OSStatInit(),

OSTaskStat() and, OSTimeDlyHMSM().

Appendix E

Bibliography

Allworth, Steve T.

Introduction To Real-Time Software Design

New York, New York

Springer-Verlag, 1981

ISBN 0-387-91175-8

Bal Sathe, Dhananjay

Fast Algorithm Determines Priority

EDN (India), Sept. 1988, p.237

Comer, Douglas

Operating System Design, The XINU Approach

Englewood Cliffs, New Jersey

Prentice-Hall, Inc., 1984

ISBN 0-13-637539-1

Deitel, Harvey M. and Michael S. Kogan

The Design Of OS/2

Reading, Massachusetts

Addison-Wesley Publishing Company, 1992

ISBN 0-201-54889-5

Ganssle, Jack G.

The Art of Programming Embedded Systems

San Diego, California

Academic Press, Inc., 1992

ISBN 0-122-748808

Gareau, Jean L.

“Embedded x86 Programming: Protected Mode”

Embedded Systems Programming, April 1998 p80-93

Halang, Wolfgang A. and Alexander D. Stoyenko

Constructing Predictable Real Time Systems

Norwell, Massachusetts

Kluwer Academic Publishers Group, 1991

ISBN 0-7923-9202-7

Hunter & Ready

VRTX Technical Tips

Palo Alto, California

Hunter & Ready, Inc., 1986

Hunter & Ready

Dijkstra Semaphores, Application Note

Palo Alto, California

Hunter & Ready, Inc., 1983

Hunter & Ready

VRTX and Event Flags

Palo Alto, California

Hunter & Ready, Inc., 1986

Intel Corporation

iAPX 86/88, 186/188 User’s Manual: Programmer’s Reference

Santa Clara, California

Intel Corporation, 1986

Kernighan, Brian W., Ritchie, Dennis M.

The C Programming Language, Second Edition

Englewood Cliffs, N.J.

Prentice Hall, 1988

ISBN 0-13-110362-8

Klein, Mark H., Thomas Ralya, Bill Pollak, Ray Harbour Obenza, and Michael Gonzlez

A Practioner's Hardbook for Real-Time Analysis:

Guide to Rate Monotonic Analysis for Real-Time Systems

Norwell, Massachusetts

Kluwer Academic Publishers Group, 1993

ISBN 0-7923-9361-9

Labrosse, Jean J.

μC/OS, The Real-Time Kernel

Lawrence, Kansas

R & D Publications, 1992

ISBN 0-87930-444-8

Laplante, Phillip A.

Real-Time Systems Design and Analysis, An Engineer's Handbook

Piscataway, NJ 08855-1331

IEEE Computer Society Press

ISBN 0-780-334000

Lehoczky, John, Lui Sha, and Ye Ding

"The Rate Monotonic Scheduling Algorithm: Exact Characterization and Average Case Behavior"

Proceedings of the IEEE Real-Time Systems Symposium

Los Alamitos, CA, 1989, pp. 166-171. IEEE Computer Society

Madnick, E. Stuart and John J. Donovan

Operating Systems

New York, New York

McGraw-Hill Book Company, 1974

ISBN 0-07-039455-5

Ripps, David L.

An Implementation Guide To Real-Time Programming

Englewood Cliffs, New Jersey

Yourdon Press, 1989

ISBN 0-13-451873-X

Savitzky, Stephen R.

Real-Time Microprocessor Systems

New York, New York

Van Nostrand Reinhold Company, 1985

ISBN 0-442-28048-3

Wood, Mike and Tom Barrett

"A Real-Time Primer"

Embedded Systems Programming, February 1990 p20-28

Appendix F

Licensing

µC/OS-II is a great real-time kernel and has proven itself in countless applications all around the world. Also, a number of Colleges and Universities are using µC/OS to teach real-time software.

µC/OS-II’s source and object code can be freely distributed (to students) by accredited Colleges and Universities without requiring a license, as long as there is no commercial application involved. In other words, no licensing is required if µC/OS-II is used for educational use.

You MUST obtain an 'Object Code Distribution License' to embed µC/OS-II in a commercial product. In other words, you must obtain a license to put µC/OS-II in a product that is sold with the intent to make a profit. There will be a license fee for such situations and you will need to contact me (see below) for pricing.

You MUST obtain an 'Source Code Distribution License' to distribute µC/OS-II’s source code. Again, there will be a fee for such a license and you will need to contact me (see below) for pricing.

You can contact me at:

Jean.Labrosse@uCOS-II.com

Or,

Jean J. Labrosse

9540 NW 9th Court

Plantation, FL 33324

U.S.A.

1-954-472-5094

1-954-472-7779 (FAX)

µC/OS-II Web site

The µC/OS-II WEB site (www.uCOS-II.com) contains the following information:

∙News on µC/OS and µC/OS-II,

∙Bug fixes,

∙Availability of ports,

∙Answers to frequently asked questions (FAQs),

∙Application notes,

∙Books,

∙Classes,

∙Links to other WEB sites, and