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Osek turbo
 

Osek turbo

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    Osek turbo Osek turbo Presentation Transcript

    • T S PRADEEPKUMAR
      SCS, VIT University
      OSEK/VDXAReal Time Operating System
    • Automotive Software Standards
      Introduction to OSEK/VDX
      OSEK/VDX Characteristics and Specification
      OSEK Architecture
      Conformance Classes (CC)
      Tasks Concepts
      Interrupts Processing
      Events
      Scheduling Policies
      Other OS Services
      Topics for discussion
    • Automotive Software Standard
      • AUTOSAR
      • Automotive Open System Architecture
      • OSEK/VDX
      • Open systems and the corresponding interfaces for automotive electronics / Vehicle Distributed eXecutive
      • MISRA C
      • Motor Industries Software Reliability Association
    • OSEK/VDX Characteristics
      • Scalability
      • Used for wide range of control units for 8bit to 32 bit controllers
      • Uses four conformance classes that specifies the main features
      • Portability of software
      • ISO/ANSI-C Standard interface between the application and the OS
      • Configurability
      • Standard configurable information is provided with the help of OIL (OSEK Implementation Language)
      • Statically allocated OS
      • To simplify, The OS, application tasks, resources and services are requested to define at the compile time
    • OSEK/VDX Specification
      • Three Processing Levels
      • Interrupt Level
      • A logical level for OS Activities
      • Task Level
      The interrupt levels are assigned higher priorities than the task levels
      • In addition
      • OS Services provided for task management, event management, resource, counter, alarm and error treatment
    • OSEK/VDX Specification
    • OSEK/VDX Architecture
    • OSEK COM
      • The OSEK standard comprises also an agreement on interfaces and protocols for in-vehicle communication called OSEK COM
      • An Interaction layer which provides communication services for the transfer of application messages.
      • A Network layer which provides services for the unacknowledged and segmented transfer of application messages
      • A Data link layer interface which provides services for the unacknowledged transfer of individual data packets over a network to the layers above.
    • OSEK NW
      • Very often electronic control units (ECU) made by different manufacturers are networked within vehicles by serial data communication links.
      • For this reason the standard propose a Network Management system (OSEK NM) that provides standardized features which ensure the functionality of inter-networking by interfaces.
    • OSEK/VDX Architecture
      • Traditional Fixed Priority Approach
      • Each task in the system may be
      • Basic Task (BT)
      • Extended Task (ET)
      • Each Task will be assigned a fixed Priority (assigned at compile time)
    • OSEK/VDX Architecture
      • Conformance Classes
      • To provide support for different features and requirements of the application in terms of number of tasks, memory consumption, etc
      • BCC1
      • Only basic tasks limited to one activation request per task and one task per priority, while all tasks have different priorities.
      • BCC2
      • Like BCC1, plus more than one activation request per task and more than one task per priority.
      • ECC1
      • Like BCC1, plus extended tasks.
      • ECC2
      • Like ECC1, plus more than one task per priority and multiple requesting of task activation allowed for basic tasks.
    • Conformance Classes
    • Tasks Concepts
      • Basic Task
      • Basic tasks only release the processor, if
      • they terminate
      • the OSEK operating system switches to a higher-priority task, or interrupt occurs which cause the processor to switch to an interrupt service routine (ISR).
      • Extended Tasks
      • In contrast to basic tasks extended tasks are allowed to use the operating system call WaitEvent, which may result in a waiting state
      • The waiting state allows the processor to be released and to be reassigned to a lower-priority task without the need to terminate the running extended task
      • In view of the operating system, management of extended tasks is, in principle, more complex than management of basic tasks and requires more system resources
    • Tasks Concepts
    • Tasks Concepts
      • Extended Tasks have four task states:
      • Running
      • Only one task can be in this state at any point in time
      • Ready
      • The scheduler decides which ready task is executed next
      • Waiting
      • A task cannot continue execution because it has to wait for at least one event
      • Suspended
      • The task is passive and can be activated
    • Interrupt Processing
      In particular, the standard provides two kind of ISR handlers:
      • ISR Category 1
      • ISR does not use an OS Service.
      • No OS calls from the handler
      • The designer is free to write his own handler
      • These are the faster highest priority Interrupt
      • ISR Category 2
      • ISR is handled by the OS
      • So OS calls can be called from the handler
    • Events
      • Event Mechanism is provided only for Extended Tasks
      • Each (ET) owns a set of events that can be triggered by other BT or ET or even ISR Category 2
      • The behavior of an ET is to wait for an Asynchronous Event calling the OS Service WaitEvent()
      • Events can be set only if the task is not in the suspended state
    • Scheduling Policy
      • Mixed Preemptive Scheduling
      • Non Preemptive scheduling
    • Scheduling Policy
      • Mixed Preemptive Scheduling
      • Since preemptiveness is a task attribute, preemptive and non-preemptive tasks can be mixed in the same application.
      • The running task will influence the policy really used.
    • Other OS Services
      • Alarm Management
      • Error Management
      • Application Error
      • Fatal Error
      • Leads to System Shutdown
      • System Startup