Databases are the means of choice for managing embedded networks. Although it is possible (and supported) in principle to run a network without a database, using a database is highly recommended to maintain a consistent set of network parameters for all nodes in the network. This is especially true for FlexRay, which requires you to set up about 30 parameters consistently to get a running network.

Additionally, a database can manage the contents of the data exchanged over the network. You can store frames and signals running on the network in a database, as well as information about which ECU is transmitting or receiving which data. This information also is needed for each node in the network.

For an NI-XNET interface to communicate with hardware products on the external network, NI-XNET must understand the communication in the actual embedded system, such as the vehicle. This embedded communication is described within a standardized file, such as CANdb (.dbc), FIBEX (.xml), AUTOSAR (.arxml), or LIN Description File (.ldf). Within NI-XNET, this file is referred to as a database. The database contains many object classes, each of which describes a distinct entity in the embedded system.

  • Database: Each database is represented as a distinct instance in NI-XNET. Although the database typically is a file, you also can create the database at run time (in memory).
  • Cluster: Each database contains one or more clusters, where the cluster represents a collection of hardware products connected over a shared cabling harness. In other words, each cluster represents a single CAN, FlexRay, or LIN network. For example, the database may describe a single vehicle, where the vehicle contains one CAN cluster Body, another CAN cluster Powertrain, one FlexRay cluster Chassis, and a LIN cluster PowerSeat.
  • ECU: Each Electronic Control Unit (ECU) represents a single hardware product in the embedded system. The cluster contains one or more ECUs connected over a CAN, FlexRay, or LIN cable. It is possible for a single ECU to be contained in multiple clusters, in which case it behaves as a gateway between the clusters.)
  • Frame: Each frame represents a unique unit of data transfer over the cluster cable. The frame bits contain payload data and an identifier that specifies the data (signal) content. Only one ECU in the cluster transmits (sends) each frame, and one or more ECUs receive each frame.
  • Signal: Each frame contains zero or more values, each of which is called a signal. Within the database, each signal specifies its name, position, length of the raw bits in the frame, and a scaling formula to convert raw bits to/from a physical unit. The physical unit uses a double-precision floating-point numeric type.

Other object classes include the Subframe, LIN Schedule, and LIN Schedule Entry.

Note that Ethernet interfaces currently do not support databases.