Introduction to RTOS m4
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Introduction to RTOS
About SwiftACT
• A Technology services startup company
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Under establishment
• Areas of specialties:
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Mobile telecommunication services development
Embedded systems development
• Types of services:
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Consultation
Managed services
Sourcing
Training
Amr Ali Abdel-Naby@2010
Introduction to RTOS
About Me
• Graduated 2004
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ECE, ASU: 5 yrs distinction
• 5+ years in embedded systems development
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SDLC, Apps, MW, DD, Porting, ...
• 3+ years in SW engineering
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PSP, CMMI, Systematic reuse, ...
• 3+ years in SW testing
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IBM certified, ISTQB certified, ...
Amr Ali Abdel-Naby@2010
Introduction to RTOS
Copyright
• Materials in this course is the property of Amr Ali Abdel-Naby.
• Reproduction or transmission of the materials in any manner
without the copyright owner permission is a law violation.
Amr Ali Abdel-Naby@2010
Introduction to RTOS
Outline
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Introduction
Tasks
Semaphores
Message Queues
Other Kernel Objects
Other Kernel Services
Amr Ali Abdel-Naby@2010
Introduction to RTOS
Outline
•
•
•
•
•
•
Introduction
Tasks
Semaphores
Message Queues
Other Kernel Objects
Other Kernel Services
Amr Ali Abdel-Naby@2010
Introduction to RTOS
Indirect Message Passing
• Messages are sent from task to task via queues.
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Not sent directly from task to task
• Message queues are separate RTOS objects.
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Caution: Messages are copied by the RTOS as they enter/exit the
queue.
They are copied twice.
Amr Ali Abdel-Naby@ 2009
Real-Time Operating Systems
Asynchronous Data Communication
• Loosely-coupled operation: Sender shoots & forgets
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Task delivers messages to RTOS, then continues execution.
Never waits
Message normally deposited at the tail of the receiver’s queue.
Hopes that receiver task will fetch the message
Content/Structure of message payload are irrelevant to RTOS.
Variable data, pointers, structures, unions, …
Amr Ali Abdel-Naby@ 2009
Real-Time Operating Systems
Message Queue
Message delivered
(msgs--)
Message delivered
(msgs--)
Message delivered
(msgs = 0)
Queue created
(msgs = 0)
Empty
Not Empty
Message arrived
(msgs = 1)
Message arrived
(msgs = queue length)
Message arrived
(msgs++)
Amr Ali Abdel-Naby@2010
Full
Introduction to RTOS
Message Queues: 4 Traditional
Usages
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Non-interlocked one-way data communication
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Interlocked one-way data communication
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= Non-interlocked one-way data communication + Binary semaphore
Binary semaphore used for handshake (wait/signal semaphore usage)
Interlocked two-way data communication
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= Indirect message passing
2 message queues
Handshake messaging
Broadcast communication
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= Indirect message passing + multiple receivers
Amr Ali Abdel-Naby@ 2009
Real-Time Operating Systems
Examples: Wait/Signal, Credit
Tracking
Non-interlocked, 1-way
Interlocked, 1-way
Interlocked, 2-way
Amr Ali Abdel-Naby@ 2009
Real-Time Operating Systems
Typical Message Queue Operations
• Message queue creation and deletion
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Create
Delete
• Sending and receiving messages
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Send: non blocking, block with timeout, or block forever
Receive: destructive read, or non-destructive read
Broadcast
• Obtaining message queue information
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Show queue info
Show queue’s blocked task-waiting list
Amr Ali Abdel-Naby@2010
Introduction to RTOS
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