Bus Overview

A Virtual bus allows you to transmit messages between nodes operating within the context of the MxSuite test environment. In MxVDev you can configure as many Virtual Buses as you need. Typically for testing purposes you have two or more nodes on a bus. Let’s review some common node types:

Real Nodes (Hardware)

Real ECUs on an actual bus can be connected to a virtual bus. To attach real nodes to your virtual bus, install a Bus Interface Device and configure its corresponding Transform in MxTransIt. Then connect the Bus Interface Device Transform to CAN or LIN Transmit and Receive Transforms. Once configured, all traffic on the actual bus is transmitted on the virtual bus and all traffic on the virtual bus exists on the actual bus. In this way, real nodes outside the PC are seen as nodes on the Virtual Bus. The interface devices are not nodes themselves, but a connection to the actual bus and its nodes. For more detail, see CAN Transmit Driver.

Nodes Simulated by an MxVMC

The MxVMC operates within the Test Harness and can be configured to function as a node on a Virtual bus. The MxVMC provides the capability to simulate complex nodes such as a motor or controller. You could have several MxVMCs each operating as individual nodes. For an example, see the Multi-VMC Sample Project. For more details, see MxVMC CAN Sub-System.

Nodes Simulated by MxVDev

MxVDev itself can interface with the Virtual Buses, and send and receive traffic on the buses. It can simulate the operation of one or more nodes, on several buses. The interface is defined with the CAN Bus Configuration box.

Nodes Simulated by Transforms

You can construct your own nodes with fully customized behavior using Transforms in MxTransIt. You can build a closed-loop node with the CAN Receive Driver and the CAN Transmit Driver Transforms. For a simple example, see CAN Transmit Driver - Example. (You can use the LIN Receive and Transmit Driver Transforms in the same way on a LIN bus.)

Nodes Under Test (NUT)

To test a node, you can send and receive bus messages intended for that node from MxVDev TestCases to the bus. The node should be marked in the Receive From column of the CAN Bus Configuration. Usually a node under test is a real node, but it could be simulated by a Transform.

Periodic and Spontaneous CAN Messages

CAN messages are defined in the DBC file. The file specifies the contents and whether the message is periodic or spontaneous:

•Periodic - a message is sent automatically at specified intervals, for example, once every 10 ms. See Automatic Message Transmission.

•Spontaneous - a message is sent when its contents change.

For more detail, see Working with a CAN Bus.

LIN Messages

LIN messages are defined in the LDF. Transmission of LIN messages is controlled by a Schedule Table, which is part of the LDF.

In MxTransIt, you can use Transforms to send or receive bus messages. Specify the DBC or LDF file in the Transform's properties. See:

•CAN Transforms (includes examples)

•LIN Transforms

•MOST Transforms

This method provides the most flexibility and capabilities.

To create a bus in MxVDev, use the Network Configuration dialog to load its DBC or LDF file into MxVDev. Once the file has been loaded, the defined messages can be added to TestCases with the Pick Signals dialog. You can view the signals in the Signal Dictionary, but they can be changed in the DBC or LDF file only.

Also use the Network Configuration dialog to specify if a node is under test or simulated.

MxSuite supports the indicated Bus type/Bus Interface Device combinations:

For more information, see Bus Interface Devices.