systemAutomotive Embedded Systems part2(OSEK/VDX) Operating System

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Automotive Embedded
Systems part2
(OSEK/VDX)
Operating System
ENG.KEROLES SHENOUDA
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OSEK/VDX
Operating System
it's time to wake up 
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AUTOSAR
 AUTOSAR = AUTomotive Open System Architecture
 More informations on the site: http://www.autosar.org
3Will talk in details in the next parts. But Now I need to focus
on the AUTOSAR OS

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AUTOSAR
 AUTOSAR = AUTomotive Open System Architecture
 More informations on the site: http://www.autosar.org
4Will talk in details in the next parts. But Now I need to focus
on the AUTOSAR OS
Application layer: software
components which implement ECU
functions
RTE: middleware which
implements and access to the
hardware resources
for the application layer

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AUTOSAR
 AUTOSAR = AUTomotive Open System Architecture
 More informations on the site: http://www.autosar.org
5Will talk in details in the next parts. But Now I need to focus
on the AUTOSAR OS
Services layer: AUTOSAR OS
kernel, communication protocols,
NVRAM
access services, diagnostic services.
ECU abstraction layer: high level
access to on-board and off-board
devices

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AUTOSAR
 AUTOSAR = AUTomotive Open System Architecture
 More informations on the site: http://www.autosar.org
6Will talk in details in the next parts. But Now I need to focus
on the AUTOSAR OS
Micro-controller abstraction layer:
low level access to on-board devices.
Complex drivers: free slot in the
architecture to implement special
device drivers

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AUTOSAR OS
 AUTOSAR OS is the specification of an OS kernel
for AUTOSAR architecture.
 It is based on OSEK/VDX OS :
 It adds new concepts: OS-Application, Schedule
Table, Global Time, Software Counter.
 the main improvement is the addition of configurable
mechanisms for error detection in the kernel (called
“protection facilities”) This rectify the OSEK/VDX
OS inability to support critical systems
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AUTOSAR OS
 AUTOSAR OS is the specification of an OS kernel for
AUTOSAR architecture.
 It is based on OSEK/VDX OS :
 Software counters
 Schedule Tables
 Global time synchronization
 Stack monitoring
 OS Applications
 Protection mechanisms
 the main improvement is the addition of configurable
mechanisms for error detection in the kernel (called
“protection facilities”) This rectify the OSEK/VDX OS
inability to support critical systems
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What is the OSEK-VDX ?
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OSEK/VDX Overview
 OSEK : "Open System sand the Corresponding
Interfaces for Automotive Electronics"
 VDX : Vehicle Distributed executive
 The OSEK API was designed by automotive suppliers.
 System specification (architecture, interfaces et
behavior) for automotive electronic embedded systems
(http://www.osek-vdx.org )
 OSEK/VDX (OSEK Vehicle Distributed eXecutive)
 Operating System(OS)
 Communications(COM)
 Network Management(NM)
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OSEK Specifications
 OSEK OS
 serves as a basis for the controlled real-
time execution of concurrent applications
 OSEK OIL
 OIL provides a possibility to configure an
OSEK/VDX application inside a particular
CPU
 OSEK COM / NM
 provides interfaces and protocols for the
transfer of data within vehicle networks
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Goals & Motivations
 High expenses coming from the development
and/or port of operating system
 No interoperability of systems built by
different providers
 Standardized interfacing features
 Utilization of the existing resources in the
vehicle, enhance the performance of the overall
system without requiring additional hardware.
 Basic software reusability, Application
portability.
12Reusability
Distributed functions

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Where is OSEK compared to other OS ?
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ECU software architecture
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OSEK/VDX OS
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Services of OSEK:
• Task services
• Synchronization services (events)
• Mutual exclusion services (resources)
• One-shot and periodical services (counters and alarms)
• Interrupt management services
• Communication services
• System services and error management

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OSEK OS + OIL Application
 Objects of an OSEK application are all defined when the
application is designed
 Objects are static.
 i.e: there are no creation/deletion of tasks, resources, ...dynamically
during the execution of the application.
 Data structures are used to store the properties of the objects
and are defined
statically when the application is built.
 A language has been defined (and standardized) to define the
attributes of the objects in a simple way:
 OIL: OSEK Implementation Language
 The OIL syntax is a simple one: based on objects (tasks,
resources, …) with a value for each attribute. Some attributes
have sub-attributes.
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Applications
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So We will make our labs on
Trampoline, So
What is Trampoline?
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What is Trampoline?
 Trampoline is an open platform for small embedded systems with
real-time constraints
 It is based on the OSEK/VDX OS and AUTOSAR OS standards
 So it is compatible with OSEK/VDX OS and AUTOSAR OS API.
 OSEK/VDX and Autosar os are static operating systems.
 That means the objects of the application, tasks, events, resources, . . . ,
cannot be created or deleted during the execution of the application. All
objects are statically designed
 and instead of forcing the user to describe the application in C, a work
that can be error prone, a specfic language is used, OIL or XML2.
 A compiler, goil, is used to translate the description in the equivalent C
structures. goil performs verifications too.
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Tasks in OSEK
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Tasks in OSEK
 Tasks are « active » elements of the application
2 categories of tasks exist in OSEK/VDX:
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Basic tasks Extended tasks
A basic task is a sequential C
code that must terminate
The task that are
able to wait for an
event are called
Extended tasks

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Basic task states
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Basic tasks only release
the processor, if
• they terminate,
• the OSEK operating system
switches to a higher-priority
task, or
• an interrupt occurs which
causes the processor to
switch to an interrupt service
routine (ISR).
The state model of basic tasks is nearly identical to the extended
tasks state model. The only exception is that basic tasks do not
have a waiting state.

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States and status transitions for basic tasks
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Extended tasks have four task states:

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OSEK scheduling policy
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OSEK scheduling policy
 Scheduling is done dynamically during the execution of the application.
 Tasks have a fixed priority
 The priority of a task is given at design stage;
 The priority does not change (almost, taking and releasing resources may change
the priority);
 No round-robin.
 If more than one task have the same priority, tasks are run one after the other.
ie a task may not preempt a task having the same priority
 Tasks may be preemptable or not (almost)
 This property is defined at design stage.
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Scheduling modes
 “Full preemptive”:
 All tasks are preemptable.
 “Full non preemptive”:
 All tasks are non-preemptable
 “Mixed”:
 Each task may be configured as preemptable or non-preemptable
 It is the most flexible model.
 For instance, a very short task (in execution time) may be configured as non-
preemptable because the context switch is longer than its execution.
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Processing Levels
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 The OSEK operating system enables a
controlled real-time execution of several
processes which appear to run in parallel
 Entities which are competing for the CPU
are:
 Interrupt service routines
 Tasks
 OSEK defines three processing levels:
 Interrupt level
 Logical level for scheduler
 Task level
 Priority rules:
 Interrupts have precedence over tasks

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Full preemptive
 Full preemptive scheduling will put the running task into the ready state,
as soon as a higher-priority task has got ready. The task context is saved
so that the preempted task can be continued at the location where it was
preempted.
 EX: task T2 with the lower priority does not delay the scheduling of task
T1 with higher priority.
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Full non preemptive
 the non preemptable section of a running task with lower priority delays the
start of a task with higher priority up to the next point of rescheduling
 EX: task T2 with the lower priority delays task T1 with higher priority up to
the next point of rescheduling (in this case termination of task T2).
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Tasks’ services
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TASK(myTask)
{
//Task’s instructions
…
//Task_Service API
}

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TerminateTask Service
StatusType TerminateTask(void);
 StatusType is an error code:
 E_OK: no error
 E_OS_RESOURCE: the task hold a resource
 E_OS_CALLEVEL: the service is called from an interrupt
 The service stops the calling task. The task goes from
running state to suspended state.
 A task may not stop another task
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TASK(myTask)
{
//Task’s instructions
…
TerminateTask();
}

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ActivateTask service:
StatusType ActivateTask(TaskType <TaskId>);
 The argument is the id of the task to activate.
 StatusType is an error code:
 E_OK: no error
 E_OS_ID: invalid TaskId (no task with such an id)
 E_OS_LIMIT: too many activations of the task
 This service puts the task <TaskId> in ready state
If the activated task has a higher priority (preemptive), the calling task is
put in the ready state. The new one goes in the running state.
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TASK(myTask)
{
//Task’s instructions
…
ActivateTask(T2);
…..
}

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Example 1 34

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Example 2 35

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Example 3 36

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ChainTask service
StatusType ChainTask(TaskType <TaskId>);
 The argument is the id of the task to activate;
 StatusType is an error code:
 E_OK: No error
 E_OS_ID: invalid TaskId (no task with such an id)
 E_OS_LIMIT: too many activations of the task
 This service puts task <TaskId> in ready state, and the calling task
in the suspended state.
 This service replaces TerminateTask for the calling task
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Example 4
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Be HapPy
Now the Lab Time 
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40
• The requirement
• Two Basic Tasks T1 And T2
• T1 (autosatart)will toggle led 0
• T2 Will toggle led 1
• T1(priority) > T2(priority)
• Led0 @ PortA bin 4
• Led1 @ PortA pin 5
Led0
Led1

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First Write the oil File 41
We will learn
the oil
Parameters
step by step
Through labs


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The Oil File
 PRIORITY : integer: the
priority of the process.
 ACTIVATION : integer:
the number of activation of
a task. 1 for and extended
task or an ISR.
 AUTOSTART: boolean :
true if the process is an
autostart task, false otherwise.
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The lab1.c
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The output
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45
• The requirement
• Two Basic Tasks T1 And T2
• T1 (autosatart)will toggle led 0
• T2 Will toggle led 1
• T1(priority) > T2(priority)
• Led0 @ PortA bin 4
• Led1 @ PortA pin 5
Led0
Led1

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lab2
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lab2
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48
Oil file
Lab2.c

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49
• The requirement
• Two Basic Tasks T1 And T2
• T1 (autosatart)will toggle led 0
• T2 Will toggle led 1
• T1(priority) < T2(priority)
• Led0 @ PortA bin 4
• Led1 @ PortA pin 5
Led0
Led1

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Oil file
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lab3
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Lab3.c

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lab3
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Lab3.c

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lab3
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Lab3.c

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Tasks’ synchronization
 Synchronization of tasks: A task should be able to wait an external
event (a verified condition).
 To implement this feature, OSEK uses events.
 Task’s model is modified to add a new state: waiting.
 The task that are able to wait for an event are called Extended tasks
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Will go #in_depth in the next session
get Break 
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References
 Embedded Microcomputer Systems Real Time Interfacing Third
Edition Jonathan W. Valvano University of Texas at Austin.
 MicroC/OS-II the real-time kernel second edition jean j.labrosse.
 RTOS Concepts http://www.embeddedcraft.org.
 OSEK/VDX Operating System Specification 2.2.3
 AUTOSAR Layered Software Architecture
 The Trampoline Handbook release 2.0
 Trampoline (OSEK/VDX OS) Test Implementation -Version 1.0,
Florent PAVIN ; Jean-Luc BECHENNEC
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References
 Trampoline:an open platform for (small) embedded systems based on
OSEK/VDX and AUTOSAR
http://trampoline.rts-software.org/
Jean-Luc Béchennec1;2, Sébastien Faucou1;3
1IRCCyN (Institute of Research in Communications and Cybernetics of Nantes)
2CNRS (National Center for Scientific Research) / 3University of Nantes
10th Libre Software Meeting
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References
 Real Time Systems (RETSY)
Jean-Luc Béchennec - Jean-Luc.Bechennec@irccyn.ec-nantes.fr
Sébastien Faucou - Sebastien.Faucou@univ-nantes.fr
jeudi 12 novembre 15
 AUTOSAR Specification of Operating System V5.0.0 R4.0 Rev 3
 OSEK OS Session Speaker Deepak V.
M.S Ramaiah School of Advanced Studies - Bangalore 1
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