To understand the concept behind Adaptive Platform, there is a few information prerequisites to know, that strongly differs from the classical concept used in the automotive environment until now. This is the service oriented data transmission.
Some/IP – Scalable Service-Oriented Middleware over IP
Some/IP is short for Scalable Service-Oriented Middleware over IP and brings a new service-oriented philosophy for data transmission into the vehicle as classic bus systems like CAN, LIN and FlexRay use signal-oriented data transmission.
Recap Signal-Oriented Data Transmission
With signal-oriented data transmission, information is sent when the transmitter sees a need, for example, when there are updates or changes in values. This is regardless of whether this data is currently required by a receiver in the network and so these data transmissions can burden a network and all connected nodes.
Furthermore, most information is broadcasted in the network, i.e., everyone will receive the information and has to figure out, whether the information is relevant or not.
Service-Oriented Data Transmission
The situation is different with service-oriented data transmission. Here a sender only transmits data when at least one receiver in the network needs it. The advantage of this procedure is that the network and all connected nodes are not burdened by unnecessary data. And a sender transmits data only to a recipient which has explicitly registered for this data.
Service-oriented data transmission therefore requires that a server is somehow informed about which receivers needs which data.
A client has the possibility to subscribe to the content of a service on the server. If an event occurs, it then receives the updated data from the server. A content of a service can be subscribed to by several clients simultaneously. Subscribing to a content is done using the SOME/IP Service Discovery (Some/IP-SD)
Calling methods - Remote procedure call
Another possibility for data exchange is that information can be provided by calling a method (so-called remote procedure call). With this a function on the server side is started by the client.
Some/IP Daemon
The Some/IP Daemon is a central communication unit over which all communication within a machine takes place (if not direct inter process communication - IPC is used). Using the Service Discovery, the Daemon manages all services that are provided by the system.
Every machine has one Some/IP Daemon or better said, every instance of AUTOSAR Adaptive software has one Some/IP Daemon. An instance can e.g. also be a partition on a hypervisor.
What is a Daemon? Linux-familiar developers can skip this explanation.
A Daemon is a Linux or unix program that runs in the background. Usually, their names end with a d, e.g. Some/IPd. Daemons are often started at boot time.
Service Discovery
To make sure that a client knows which services are currently available, Some/IP-SD (Service Discovery) provides two mechanisms that allow the dynamic discovery of services.
- An Offer Service enables the server to offer all services it offers in the Network.
- The Find Services allows the Clients to ask for available service instead.
If you are familiar with AUTOSAR Classic, knowing and understanding of the signal-based data transmission approach is key for understanding a main part of the AUTOSAR Adaptive concept and key for understanding the following content.