Periodic CAN Communication in MATLAB
This example shows you how to how to configure CAN channels and messages for transmit messages periodically. 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("CANDatabasePeriodic.dbc");
txCh.Database = db;
rxCh.Database = db;
Create the CAN Messages
Create CAN messages EngineMsg
and TransmissionMsg
using the database information.
msgFast = canMessage(db, "EngineMsg")
msgFast = 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: []
msgSlow = canMessage(db, "TransmissionMsg")
msgSlow = Message with properties: Message Identification ProtocolMode: 'CAN' ID: 200 Extended: 0 Name: 'TransmissionMsg' 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 Messages for Periodic Transmission
To enable a message for periodic transmission, use the transmitPeriodic
command specifying the transmitting channel, the message to register on the channel, a state value, and the periodic rate.
transmitPeriodic(txCh, msgFast, "On", 0.100); transmitPeriodic(txCh, msgSlow, "On", 0.500);
Start the Periodic Transmission
Start the receiving channel.
start(rxCh);
Start the transmitting channel with periodic transmission configured in the previous step. Period transmission begins immediately. Allow the channels to run for two seconds.
start(txCh); pause(2);
Update Transmitted Data
To update the live messages or signal data transmitted onto the CAN bus, write new values directly to the VehicleSpeed
signal in message EngineMsg
.
msgFast.Signals.VehicleSpeed = 60; pause(1); msgFast.Signals.VehicleSpeed = 65; pause(1); msgFast.Signals.VehicleSpeed = 70; pause(1);
Alternatively, you can write new values to the Data
property of the created messages.
Receive the Messages
Stop the CAN channels and receive all periodically transmitted messages for analysis.
stop(txCh); stop(rxCh); msgRx = receive(rxCh, Inf, "OutputFormat", "timetable");
View the first few rows of the received messages using the head
function.
head(msgRx)
ans=8×8 timetable
Time ID Extended Name Data Length Signals Error Remote
____________ ___ ________ ___________________ ___________________ ______ ____________ _____ ______
0.015467 sec 100 false {'EngineMsg' } {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
0.015476 sec 200 false {'TransmissionMsg'} {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
0.11546 sec 100 false {'EngineMsg' } {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
0.21546 sec 100 false {'EngineMsg' } {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
0.31547 sec 100 false {'EngineMsg' } {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
0.41547 sec 100 false {'EngineMsg' } {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
0.51547 sec 100 false {'EngineMsg' } {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
0.51547 sec 200 false {'TransmissionMsg'} {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
Analyze the Behavior of Periodic Transmission
Analyze the distribution of messages by plotting the identifiers of each received message against their timestamps. Note the difference between how often the two messages appear according to the configured periodic rates.
plot(msgRx.Time, msgRx.ID, "x") ylim([0 400]) title("Message Distribution", "FontWeight", "bold") xlabel("Timestamp") ylabel("CAN Identifier")
For further analysis, separate the two messages into individual timetables.
msgRxFast = msgRx(strcmpi("EngineMsg", msgRx.Name), :);
head(msgRxFast)
ans=8×8 timetable
Time ID Extended Name Data Length Signals Error Remote
____________ ___ ________ _____________ ___________________ ______ ____________ _____ ______
0.015467 sec 100 false {'EngineMsg'} {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
0.11546 sec 100 false {'EngineMsg'} {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
0.21546 sec 100 false {'EngineMsg'} {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
0.31547 sec 100 false {'EngineMsg'} {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
0.41547 sec 100 false {'EngineMsg'} {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
0.51547 sec 100 false {'EngineMsg'} {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
0.61548 sec 100 false {'EngineMsg'} {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
0.71547 sec 100 false {'EngineMsg'} {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
msgRxSlow = msgRx(strcmpi("TransmissionMsg", msgRx.Name), :);
head(msgRxSlow)
ans=8×8 timetable
Time ID Extended Name Data Length Signals Error Remote
____________ ___ ________ ___________________ ___________________ ______ ____________ _____ ______
0.015476 sec 200 false {'TransmissionMsg'} {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
0.51547 sec 200 false {'TransmissionMsg'} {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
1.0155 sec 200 false {'TransmissionMsg'} {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
1.5155 sec 200 false {'TransmissionMsg'} {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
2.0155 sec 200 false {'TransmissionMsg'} {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
2.5155 sec 200 false {'TransmissionMsg'} {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
3.0155 sec 200 false {'TransmissionMsg'} {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
3.5155 sec 200 false {'TransmissionMsg'} {[0 0 0 0 0 0 0 0]} 8 {1x1 struct} false false
Analyze the timestamps of each set of messages to see how closely the average of the differences corresponds to the configured periodic rates.
avgPeriodFast = mean(diff(msgRxFast.Time))
avgPeriodFast = duration
0.1 sec
avgPeriodSlow = mean(diff(msgRxSlow.Time))
avgPeriodSlow = duration
0.50001 sec
Use canSignalTimetable
to repackage signal data from message EngineMsg
into a signal timetable.
signalTimetable = canSignalTimetable(msgRx, "EngineMsg");
head(signalTimetable)
ans=8×2 timetable
Time VehicleSpeed EngineRPM
____________ ____________ _________
0.015467 sec 0 250
0.11546 sec 0 250
0.21546 sec 0 250
0.31547 sec 0 250
0.41547 sec 0 250
0.51547 sec 0 250
0.61548 sec 0 250
0.71547 sec 0 250
Plot the received values of signal VehicleSpeed
over time and note how it reflects the three updates in message data.
plot(signalTimetable.Time, signalTimetable.VehicleSpeed) title("Vehicle Speed from EngineMsg", "FontWeight", "bold") xlabel("Timestamp") ylabel("Vehicle Speed") ylim([-5 75])
View Messages Configured for Periodic Transmission
To see messages configured on the transmitting channel for automatic transmission, use the transmitConfiguration
command.
transmitConfiguration(txCh)
Periodic Messages ID Extended Name Data Rate (seconds) --- -------- --------------- ----------------- -------------- 100 false EngineMsg 0 0 0 0 70 0 0 0 0.100000 200 false TransmissionMsg 0 0 0 0 0 0 0 0 0.500000 Event Messages None
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