Let us now examine a particularly good example of a communication bus, namely the one used to control airbags.
The airbag system of a vehicle is highly complex, and a detailed description would require more space than this book can provide. For anybody unfamiliar with the conventional structure of this system, it can be divided into three major parts:
For ordinary vehicles, because of the large number of interconnections required between these three units, the members of the system are generally all connected to each other by a ‘point-to-point’ architecture. Figure 9.1 provides an idea of this kind of structure.
However, it should be borne in mind that security architectures can be complicated to suit any requirements, and top-range vehicles can have up to 20 airbags at least (in front, at the sides, for the head, for the knees, under the knees, to prevent sliding in a collision, etc.) and a large number of sensors. In this case, the processing unit must be centralized in order to limit the lengths of the connecting cables; indeed, we can soon reach the mechanical limits on the size of the connector(s) which may include up to 100 interconnection points and which end ...