Vehicle subsystems from the internal combustion engine to powered windows are controlled by electronic control units (ECU). These units are usually dependent of each other and have to pass information between one another.
For example a control unit in the car’s automatic gearbox shifts gears based on engine revolutions per minute and throttle position. Control unit in automatic transmission runs an algorithm that determines if the gear change is required based on the data that it gets from the engine control unit (engine speed (RPM), throttle position, emission sensors...). To ensure smooth gear shifting engine speed has to be adjusted to the next gear. Therefore both control units have to constantly communicate with each other to ensure correct operation.
Another example are powered windows in a road vehicle. Their upward and downward motion is controlled by an electronic control unit. This control unit switches the electric motor in the correct direction and also stops the electric motor when the window is in the fully closed or fully opened position. The electronic control unit gets messages to move windows from other control units. For example it can get an order from a control unit that checks the position of dashboard buttons or from a unit that receives signals from a vehicle remote control. Each of the mentioned control units performs its task and signals other control units to perform a task that is required from them. The messages can go either way. For example the window control unit can send a message back to other control units that the window is fully closed or fully opened.
As we can see from the previous example a single unit works only if it is connected to other units. Message transfer between units could be made with direct connections based on the dependency of electronic control units.
Electronic control units connected based on information flow between them
Electronic subsystems on modern road vehicles are usually controlled by more then 150 ECUs. These control units are highly dependent of each other and are connected to a single or multiple serial networks.
On a serial network data is being transmitted bit by bit onto a network. Each device can read all of the messages on the network but responds only to those that are meant for it. To ensure that critical messages get to their recipients with the least possible delay message priority is based on message importance.
Electronic control units connected on to a serial bus
Communication networks in modern road vehicles connect all of the electronic subsystems together. With transfer speeds of up to 10 Mb/s large amounts of data can be generated. With Dewesoft, we can decode and store this data.
Dewesoft device connected on to a serial bus