AUTOSAR Methodology

AUTOSAR Methodology

AUTOSAR Methodology- Sequence of Steps to develop an AUTOSAR system:

Autosar Methodology defines the sequence of steps/ activities to develop an AUTOSAR system. Nevertheless the implementation of a software component is more or less independent from ECU configuration. This is a key feature of the AUTOSAR methodology.
For the sake of conceptual understanding lets understand The AUTOSAR methodology from a theoretical perspective and then we can discuss the same from a tools perspective. The first step in the sequence of Autosar development is the system configuration input. The System configuration input is the architectural design. The software components and the hardware have to be selected, and overall system constraints have to be identified. The system configuration input will contain information about the software components, ECU resources and System constraints. Once the high level design is available then the second step is to map the software components to the ECUs with regards to the resources and timing requirements. The output file is called a System Configuration Description file. The next step is to extract the ECU specific information and configure the ECU with all the necessary information for implementation like task scheduling, necessary BSW (basic software) modules, configuration of the BSW, assignment of runnable entities to tasks, etc. The output is an ECU configuration Description file. The last step is to generate the executable file which can be flashed in the hardware(ECU).

Figure: AUTOSAR Methodology from a theoretical perspective

However, The AUTOSAR methodology is slightly different when explained from the tools perspective. Now let us see the sequence of steps involved in the AUTOSAR methodology when viewed from a tools perspective. We use an AUTOSAR authoring tool to create a high-level design which includes- Software Component description, ECU resource Description and System Description file (including the communication matrix, topology etc). Once we have these three components then the software development process using AUTOSAR methodology can be largely broken into two pieces namely, application software development and ECU configuration process.
In the application software component(SWC) development process, SWC description file which describes the software components that need to be developed is taken as input.
We may have three software components, for example, Controller software component, Dial LED software component and heating element software component. We build a system level file (arxml file) using Autosar Authoring tools.
The next step is to convert the system level file into a <*.c> and <*.h> code. Many authoring tools have this feature. This <*.c> and <*.h> code is a generic code which only contains definition of the interface that connect with RTE and SWC, including such information as declarations of API functions, SWC data structures and Runnable Entity prototypes.
For example, these header files (skeletal) allow the developer to start implementation of the SWC without having specific knowledge of the underlying basic software and hardware. These Header files are then imported into a model based code development environment to generate the actual executable code or a manual coding mechanism can be used to build the application software components which is a <*.c> and <*.h>.
In the ECU configuration process, we use the Software Component description, ECU resource Description and System Description file to generate the system Description. The System description has all the mappings i.e., it has all the details of ECUs, the software components that are mapped to the ECUs and the details of the communication matrix, topology etc. A BSW configuration tool is used to configure the ECU. A BSW configuration tool will have to do RTE Generation, OS Generation, BSW Generation and MCAL configuration. The output will be a <*.c> and <*.h>. This <*.c> and <*.h> is integrated with the <*.c> and <*.h> files generated in the application software component development process and a final make file is generated.

Figure: AUTOSAR Methodology explained from a tools perspective