This example shows you how to use the automated CAN message transmit features of Vehicle Network Toolbox™ to send messages on event. It uses Vector Virtual CAN channels connected in a loopback configuration. As this example is based on sending and receiving CAN messages on a virtual network, running Vehicle CAN Bus Monitor in conjunction may provide a more complete understanding of what the code is doing. To run Vehicle CAN Bus Monitor, open and configure it to use the same interface as the receiving channel of the example. Make sure to start Vehicle CAN Bus Monitor before beginning to run the example in order to see all of the messages as they occur.
Create the CAN Channels
Create CAN channels on which to use the automated message transmit commands.
txCh = canChannel('Vector', 'Virtual 1', 1); rxCh = canChannel('Vector', 'Virtual 1', 2);
In this example, you will use a CAN database file to define and decode messages. Open the database and attach it to the CAN channels.
db = canDatabase('demoVNT_CANdbFiles.dbc'); txCh.Database = db; rxCh.Database = db;
Create the CAN Message
You can create a CAN message to register for event transmit using the database information.
msgEngineMsg = canMessage(db, 'EngineMsg');
Configure the Message for Event Transmit
To configure a message for event transmit, use the
transmitEvent command to specify the channel, the message to register on the channel, and a mode value.
transmitEvent(txCh, msgEngineMsg, 'On');
Start the Event Message Transmit
Start the channels and write the new values to either the Data property or directly to the signals to trigger automatic event-based transmission of the message onto the CAN bus.
start(rxCh); start(txCh); msgEngineMsg.Data = [250 100 0 0 20 0 0 0]; pause(1); msgEngineMsg.Signals.VehicleSpeed = 60; stop(txCh); stop(rxCh);
Analyze the Event Transmit Behavior
The receiving channel now has two messages available, corresponding to the two updates that resulted in two transmits.
rxCh = Summary of CAN Channel using 'Vector' 'Virtual 1' Channel 2. Channel Parameters: Bus Speed is 500000. Bus Status is 'N/A'. Transceiver name is ''. Serial Number of this device is 0. Initialization access is allowed. 'demoVNT_CANdbFiles.dbc' database is attached. Status: Offline - Waiting for start. 2 messages available to receive. 0 messages transmitted since last start. 0 messages received since last start. Filter History: Standard ID Filter: Allow All | Extended ID Filter: Allow All
Receive and inspect each message to see that each has the data values previously set.
msgRx = receive(rxCh, Inf); msgRx(1) msgRx(1).Signals
ans = Message with properties: ID: 100 Extended: 0 Name: 'EngineMsg' Database: [1x1 can.Database] Error: 0 Remote: 0 Timestamp: 0.0196 Data: [250 100 0 0 20 0 0 0] Signals: [1x1 struct] UserData:  ans = VehicleSpeed: 20 EngineRPM: 2835
ans = Message with properties: ID: 100 Extended: 0 Name: 'EngineMsg' Database: [1x1 can.Database] Error: 0 Remote: 0 Timestamp: 1.0300 Data: [250 100 0 0 60 0 0 0] Signals: [1x1 struct] UserData:  ans = VehicleSpeed: 60 EngineRPM: 2835
View Messages Configured for Event Transmit
To see messages configured on a channel for event transmit, use the
Periodic Messages None Event Messages ID Extended Name Data --- -------- --------- --------------------- 100 false EngineMsg 250 100 0 0 60 0 0 0