AUTOSAR for dummies — #4 AUTOSAR Methodology

In this article, we will see about AUTOSAR methodology. When we consider the AUTOSAR BSW, it can be implemented in three ways in accordance to the conformance classes defined by AUTOSAR

ICC1: It is the simplest implementation class. The RTE and the whole BSW form a single cluster. The interfaces between the RTE+BSW cluster should be AUTOSAR compliant. Though projects can be released with this architecture , more often this is used when projects move from legacy structure to AUTOSAR as the first step

ICC2: ICC2 is the logical cluster of ICC3 divisions. For example all communication drivers , abstraction and services are grouped as communication stack. Similarly we have memory I/O and system stack. This would facilitate different vendors providing different stacks for a single ECU SW

ICC2

ICC3: This has the ’highest’ granularity level. All BSW modules have their own interface.

Now we can take a look at AUTOSAR SW development methodology. A brief summary of the steps involved is given below in the image below

Configuring the system is the first step of development, typically done by OEMs at the vehicle level. The input for this step is “System configuration Input”.It consists of

1. A reference to Top-Level composition.Top-level consists of a hierarchical description of all components that should be present in the system (composition is a collection of Atomic SW-Cs and Toplevel composition is the collection of all SW-Cs/compositions)
2. A reference to the Topology of the System, Topology refers to the ECUs which are present in the system and their inter-connection. Topology has reference to the ECU resource description( resources of the ECUs )
3. The system input can also contain ‘system constraints’ which forbid the mapping of certain SW-Cs to certain ECUs

If we consider a hypothetical example of a vehicle projects with below features

• Diesel Engine- Required SW-Cs: AccPed_input,EngineSpd_input,Fuel_pmpCtrl,Injector_Ctrl
• ABS and Rollover stability- Required SW-Cs:VehicleSpd_input,lateralAcc_input,WheelSpeeds
• Automatic transmission- Required SW-Cs:Spd_input, GearswtCtrl
• Adaptive cruise control- Required SW-Cs:Spd_input, ObjectDetection, CruiseSpdCtrl,StartStop

and with Topology

Now in the step ‘configure system’ , OEM will map the components to the ECUs in the topology. In this step, they could also decide on the implementations for some components, but typically such decisions are not taken at this higher level. Also, the communication matrix is created at this step, which contains the description of the communication medium between the ECUs, the data and its properties like timing, checksum, and others. The result of this step is stored in ‘System configuration Description’.There are software tools available to perform this step

In most cases, the ECUs are manufactured by different suppliers for the same vehicle. So the individual ECU specific information will be extracted from System configuration Description and will be given to Suppliers. This extract is called ECU extract

The supplier will do the configure ECU step, which includes

• defining of micro-controller port, pin assignment, Clock config, communication channel config like CAN, SPI, UART, I2C, and all HW configurations
• Defining Scheduling concept and configuring the scheduler/os
• configuring the other Basic SW, RTE

The result is stored as an ECU configuration description. In parallel to this step, the development of SW-Cs would be happening and finally, from the ECU configuration description the RTE and some parts of BSW will be generated and compiled together with SW-Cs will create the executable for a single ECU

Originally published at https://www.vtronics.in on September 21, 2019.