This virtual bus decouples the applications from the infrastructure. It communicates via dedicated ports, which means that the communication interfaces of the application software must be mapped to these ports. From an application point of view, no detailed knowledge of lower-level technologies or dependencies is required. This supports hardware-independent development and usage of application software. The applications of the different automotive domains interface the basic software by means of the RTE.
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The design model uses application software components which are linked through an abstract component, named the virtual function bus. The application software components are the smallest pieces of application software that still have a certain functionality. The software of an application can then be composed by using different application software-components. By only defining the interfaces, there is still freedom in the way of obtaining the functionality.
The virtual function bus connects the different software components in the design model. This abstract component interconnects the different application software components and handles the information exchange between them. The virtual function bus is the conceptualization of all hardware and system services offered by the vehicular system.
This makes it possible for the designers to focus on the application instead of the infrastructure software. By using the virtual function bus, the application software components do not need to know with which other application software components they communicate.
The software components give their output to the virtual function bus, which guides the information to the input ports of the software components that need that information. This is possible due to the standardized interfaces of the software components which specifies the input and output ports as well as the format of data exchange.
This approach makes it possible to validate the interaction of all components and interfaces before software implementation. This is also a fast way to make changes in the system design and check whether the system will still function. This approach uses 4 steps: Step 1: Input Descriptions The input description step contains three descriptions: Software Components: This description is independent of the actual implementation of the software component.
Among the necessary data to be specified are the interfaces and the hardware requirements. System: The system topology interconnections between ECUs need to be specified together with the available data busses, used protocols, function clustering and communication matrix and attributes e. This is an iterative process where ECU-resources and system-constraints are taken into account.
For example, there needs to be checked whether the necessary communication-speeds are met. This is based on the dedication of the application software components to each ECU.
Step 4: Generation of Software Executables Based on the configuration of the previous step, the software executables are generated. This methodology is automated by using tool-chains. All subsequent methodology steps up to the generation of executables are supported by defining exchange formats using XML and work methods for each step. This is a formal description of all methodology related information, modeled in UML.
This leads to the following benefits: The structure of the information can be clearly visualized The consistency of the information is guaranteed Using XML, a data exchange format can be generated automatically out of the meta-model and be used as input for the methodology. Easy maintenance of the entire vehicular system There are four types of membership for AUTOSAR: Core founding members Associate members Development members Core membership only is available for leading car manufacturers and Tier1; the other types of membership are open to other companies as well.
First the industry needs to gain a common understanding on the usage of models and the different levels of abstraction. The introduction of AUTOSAR in form of predefined design elements can lead to a cultural clash in the industry where the traditional development process is the waterfall.
The development of the design elements is traditionally top-down where the elements are a result of a stepwise refining of the desired concepts in the project. Support from tools and interoperability must be resolved before a successful implementation. Figure 5: Autosar Layered Architecture How are vehicle functions implemented today? These components communicate with each other via ports component view. All bus specific replications of send requests by a SWC to underlying layers and bus specific timing behavior must be done by COM or by the appropriate bus interfaces and drivers.
To decide which of the two transmission modes is selected, COM shall provide the possibility to attach a condition to each signal within an I-PDU separately. If at least a single condition defined for a signal within this I-PDU evaluates not to true, then the other mode shall be used.
These conditions shall be checked directly if a related signal or signal group is sent by the RTE. The attached condition on a signal for evaluating the transmission mode for an I-PDU is called transfer property.
A transfer property of a signal can either be triggered or pending. A transfer property of a signal with the triggeredvalue causes an immediate transmission of the I-PDU except if transmission mode periodic or none is defined for the I-PDU. If the transfer property of a signal is pending, no transmission of an I-PDU is caused. For this method signals within a signal group are treated like normal signals. Figure 4.
A detailed description of the selection of transmission modes is situated in. The client initiates the communication, requesting that the server performs a service, transferring a parameter set if necessary.
A single component can be both a client and a server, depending on the software realization. The client can be blocked synchronous communication or non-blocked asynchronous communication , respectively, after the service request is initiated until the response of the server is received.
The image gives an example how client-server communication for a composition of three software components and two connections is modeled in the VFB view. Sender-Receiver Communication: The sender-receiver pattern gives solution to the asynchronous distribution of information, where a sender distributes information to one or several receivers.
The sender is not blocked asynchronous communication and neither expects nor gets a response from the receivers data or control flow , i. It is the responsibility of the communication infrastructure to distribute the information.
A component has well-defined ports, through which it interacts with other components. A port always belongs to exactly one component. A port is either a PPort or an RPort. When a PPort of a component provides an interface, the component to which the port belongs provides an implementation of the operations defined in the Client-Server Interface respectively generates the data described in a data-oriented Sender-Receiver Interface.
It hides hardware specific properties of the CAN Controller as far as possible. Services for initiating transmission are offered by the CAN Driver and it calls the callback funtions of the CanIf module for notifying events hardware independently. A CAN controller serves exactly one physical channel.
A detailed description of the CAN bus is given in . The CAN Driver can access hardware resources and converts the given information for transmission into a hardware speci c format and triggers the transmission. Controllers by callback functions for bus-off and wake-up events.
It implements the interrupt service routines for all CAN hardware unit interrupts that are needed. It controls the basic software modules related to communication and coordinates the bus communication access requests.
The ComM shall simplify the usage of the bus communication stack for the user. It shall offer an API for disabling the sending of signals, shall be able to control more than one communication bus channel of an ECU and shall simplify the resource management by allocating all resources necessary for the requested communication mode.
The NM is used by the ComM to synchronize the control of communication capabilities across the network. The actural states of the bus corresponds to a communication mode of the ComM. The ComM requests a specific communication mode from the state manager and the state manager shall map the communication mode to a bus state.
It provides an inteface to the ComM and uses services of the network management modules. For network management data exchange the PDU Router module is bypassed.
It is used while development, manufactoring or service by external diagnostic tools . In gure 3. It acts as a user by requesting full communication from the ComM if diagnostic shall be performed. On behalf of multiplied information and the risk of inconsistency the problem can theoretically be resolved with multiple inheritances.
In practise the problems cannot be resolved; SystemWeaver does not support multiple inheritances.
In , work on the Adaptive Platform began. A first release was published in early , followed by release in October  and release in March Basic software modules made available by the AUTOSAR layered software architecture can be used in vehicles of different manufacturers and electronic components of different suppliers, thereby reducing expenditures for research and development and mastering the growing complexity of automotive electronic and software architectures. It aims to be prepared for the upcoming technologies and to improve cost-efficiency without compromising quality. Use this information to build the executable software, the code of the basic software modules and the code of the software components out of it.
Basics of AUTOSAR – Part 1