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: [1×1 struct]
Length: 8
Protocol Flags
Error: 0
Remote: 0
Other Information
Database: [1×1 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
0.045004 sec 100 0 'EngineMsg' [250,100,0,0,20,0,0,0] 8 1×1 struct 0 0
1.0556 sec 100 0 'EngineMsg' [250,100,0,0,60,0,0,0] 8 1×1 struct 0 0
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
0.045004 sec 20 2835
1.0556 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
