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Event-Based CAN Communication in MATLAB

This example shows you how to configure CAN channels and messages for transmit messages on event. It uses MathWorks virtual CAN channels connected in a loopback configuration.

As this example is based on sending and receiving CAN messages on a virtual network, running CAN Explorer in conjunction may provide a more complete understanding of what the code is doing. To run CAN Explorer, open and configure it to use the same interface as the receiving channel of the example. Make sure to start CAN Explorer before beginning to run the example in order to see all of the messages as they occur.

This example describes the workflow for a CAN network, but the concept demonstrated also applies to a CAN FD network.

Create the CAN Channels

Create CAN channels for message transmission and reception.

txCh = canChannel("MathWorks", "Virtual 1", 1);
rxCh = canChannel("MathWorks", "Virtual 1", 2);

Open the DBC-file that contains message and signal definitions, and attach it to both CAN channels.

db = canDatabase("CANDatabaseEvent.dbc");
txCh.Database = db;
rxCh.Database = db;

Create the CAN Message

Create CAN message EngineMsg using the database information.

msgEngineMsg = canMessage(db, "EngineMsg")
msgEngineMsg = 
  Message with properties:

   Message Identification
    ProtocolMode: 'CAN'
              ID: 100
        Extended: 0
            Name: 'EngineMsg'

   Data Details
       Timestamp: 0
            Data: [0 0 0 0 0 0 0 0]
         Signals: [1x1 struct]
          Length: 8

   Protocol Flags
           Error: 0
          Remote: 0

   Other Information
        Database: [1x1 can.Database]
        UserData: []

Configure the Message for Event-Based Transmission

To enable a message for event-based transmission, use the transmitEvent command specifying the transmitting channel, the message to register on the channel, and a state value.

transmitEvent(txCh, msgEngineMsg, "On");

Start the Event-Based Transmission

Start the receiving and transmitting channels.

start(rxCh);
start(txCh);

Write new values to the Data property and directly to the VehicleSpeed signal to trigger automatic event-based transmission of the message onto the CAN bus.

msgEngineMsg.Data = [250 100 0 0 20 0 0 0];
pause(1);
msgEngineMsg.Signals.VehicleSpeed = 60;
pause(1);

Stop the transmitting and receiving channels.

stop(txCh);
stop(rxCh);

Analyze the Behavior of Event-Based Transmission

The receiving channel now has two messages available, corresponding to the two updates that resulted in two transmissions.

rxCh.MessagesAvailable
ans = 2

Receive the available messages. Inspect the messages and note that each has the data values set previously to the Data property.

msgRx = receive(rxCh, Inf, "OutputFormat", "timetable")
msgRx=2×8 timetable
        Time        ID     Extended        Name                   Data              Length      Signals       Error    Remote
    ____________    ___    ________    _____________    ________________________    ______    ____________    _____    ______

    0.032835 sec    100     false      {'EngineMsg'}    {[250 100 0 0 20 0 0 0]}      8       {1x1 struct}    false    false 
    1.0606 sec      100     false      {'EngineMsg'}    {[250 100 0 0 60 0 0 0]}      8       {1x1 struct}    false    false 

Inspect the signals and note that the second instance of VehicleSpeed has the data value set previously to the VehicleSpeed signal.

signals = canSignalTimetable(msgRx)
signals=2×2 timetable
        Time        VehicleSpeed    EngineRPM
    ____________    ____________    _________

    0.032835 sec         20           2835   
    1.0606 sec           60           2835   

View Messages Configured for Event-Based Transmission

To see messages configured on the transmitting channel for automatic transmission, use the transmitConfiguration command.

transmitConfiguration(txCh)
Periodic Messages

None


Event Messages

ID  Extended   Name            Data         
--- -------- --------- ---------------------
100 false    EngineMsg 250 100 0 0 60 0 0 0

Close the Channels and DBC-File

Close access to the channels and the DBC-file by clearing their variables from the workspace.

clear rxCh txCh
clear db