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传输和接收 CAN 报文

以下示例说明如何使用 CAN 通道传输和接收 CAN 报文。它使用以环回配置形式连接的 MathWorks Virtual CAN 通道。

创建接收通道

通过指定供应商名称、设备名称和设备通道索引创建 CAN 通道以接收报文。

rxCh = canChannel('MathWorks', 'Virtual 1', 2);

检查通道

使用 get 命令获取有关所有通道属性及其当前值的更多详细信息。

get(rxCh)
        ArbitrationBusSpeed: []
               DataBusSpeed: []
          ReceiveErrorCount: 0
         TransmitErrorCount: 0
       InitializationAccess: 1
           InitialTimestamp: [0x0 datetime]
                 SilentMode: 0
           TransceiverState: 'N/A'
                   BusSpeed: 500000
               NumOfSamples: []
                        SJW: []
                      TSEG1: []
                      TSEG2: []
                  BusStatus: 'N/A'
            TransceiverName: 'N/A'
                   Database: []
         MessageReceivedFcn: []
    MessageReceivedFcnCount: 1
                   UserData: []
              FilterHistory: 'Standard ID Filter: Allow All | Extended ID Filter: Allow All'
           MessagesReceived: 0
        MessagesTransmitted: 0
                    Running: 0
                     Device: 'Virtual 1'
         DeviceChannelIndex: 2
         DeviceSerialNumber: 0
               DeviceVendor: 'MathWorks'
               ProtocolMode: 'CAN'
          MessagesAvailable: 0

启动通道

使用 start 命令将通道设置为在线状态。

start(rxCh);

传输报文

示例函数 generateMsgs 创建 CAN 报文并以不同的周期性速率传输它们。在示例中,该函数会在 CAN 总线上创建流,但它本身不是 Vehicle Network Toolbox™ 的一部分。

type generateMsgs
function generateMsgs()
% generateMsgs Creates and transmits CAN messages for demo purposes.
%
%   generateMsgs periodically transmits multiple CAN messages at various
%   periodic rates with changing message data.
%

% Copyright 2008-2016 The MathWorks, Inc.

    % Create the messages to send using the canMessage function. The 
    % identifier, an indication of standard or extended type, and the data
    % length is given for each message.
    msgTx100 = canMessage(100, false, 0);
    msgTx200 = canMessage(200, false, 2);
    msgTx400 = canMessage(400, false, 4);
    msgTx600 = canMessage(600, false, 6);
    msgTx800 = canMessage(800, false, 8); 

    % Create a CAN channel on which to transmit.
    txCh = canChannel('MathWorks', 'Virtual 1', 1);

    % Register each message on the channel at a specified periodic rate.
    transmitPeriodic(txCh, msgTx100, 'On', 0.500);
    transmitPeriodic(txCh, msgTx200, 'On', 0.250);
    transmitPeriodic(txCh, msgTx400, 'On', 0.125);
    transmitPeriodic(txCh, msgTx600, 'On', 0.050);
    transmitPeriodic(txCh, msgTx800, 'On', 0.025);
    
    % Start the CAN channel.
    start(txCh);
    
    % Run for several seconds incrementing the message data regularly.
    for ii = 1:50
        % Increment the message data bytes.
        msgTx200.Data = msgTx200.Data + 1;
        msgTx400.Data = msgTx400.Data + 1;
        msgTx600.Data = msgTx600.Data + 1;
        msgTx800.Data = msgTx800.Data + 1;
        
        % Wait for a time period.
        pause(0.100);
    end

    % Stop the CAN channel.
    stop(txCh);
end

对于该示例,运行 generateMsgs 函数以传输报文。

generateMsgs();

接收报文

generateMsgs 完成后,从通道接收所有可用报文。

rxMsg = receive(rxCh, Inf, 'OutputFormat', 'timetable');
rxMsg(1:25, :)
ans =

  25x8 timetable

        Time         ID     Extended       Name          Data        Length      Signals       Error    Remote
    _____________    ___    ________    __________    ___________    ______    ____________    _____    ______

    0.004587 sec     100     false      {0x0 char}    {1x0 uint8}      0       {0x0 struct}    false    false 
    0.0045942 sec    200     false      {0x0 char}    {1x2 uint8}      2       {0x0 struct}    false    false 
    0.0045991 sec    400     false      {0x0 char}    {1x4 uint8}      4       {0x0 struct}    false    false 
    0.0046013 sec    600     false      {0x0 char}    {1x6 uint8}      6       {0x0 struct}    false    false 
    0.0046022 sec    800     false      {0x0 char}    {1x8 uint8}      8       {0x0 struct}    false    false 
    0.029588 sec     800     false      {0x0 char}    {1x8 uint8}      8       {0x0 struct}    false    false 
    0.054593 sec     600     false      {0x0 char}    {1x6 uint8}      6       {0x0 struct}    false    false 
    0.054595 sec     800     false      {0x0 char}    {1x8 uint8}      8       {0x0 struct}    false    false 
    0.079589 sec     800     false      {0x0 char}    {1x8 uint8}      8       {0x0 struct}    false    false 
    0.10459 sec      600     false      {0x0 char}    {1x6 uint8}      6       {0x0 struct}    false    false 
    0.10459 sec      800     false      {0x0 char}    {1x8 uint8}      8       {0x0 struct}    false    false 
    0.12959 sec      400     false      {0x0 char}    {1x4 uint8}      4       {0x0 struct}    false    false 
    0.12959 sec      800     false      {0x0 char}    {1x8 uint8}      8       {0x0 struct}    false    false 
    0.15459 sec      600     false      {0x0 char}    {1x6 uint8}      6       {0x0 struct}    false    false 
    0.15459 sec      800     false      {0x0 char}    {1x8 uint8}      8       {0x0 struct}    false    false 
    0.17959 sec      800     false      {0x0 char}    {1x8 uint8}      8       {0x0 struct}    false    false 
    0.20459 sec      600     false      {0x0 char}    {1x6 uint8}      6       {0x0 struct}    false    false 
    0.20463 sec      800     false      {0x0 char}    {1x8 uint8}      8       {0x0 struct}    false    false 
    0.22959 sec      800     false      {0x0 char}    {1x8 uint8}      8       {0x0 struct}    false    false 
    0.25459 sec      200     false      {0x0 char}    {1x2 uint8}      2       {0x0 struct}    false    false 
    0.2546 sec       400     false      {0x0 char}    {1x4 uint8}      4       {0x0 struct}    false    false 
    0.2546 sec       600     false      {0x0 char}    {1x6 uint8}      6       {0x0 struct}    false    false 
    0.2546 sec       800     false      {0x0 char}    {1x8 uint8}      8       {0x0 struct}    false    false 
    0.2796 sec       800     false      {0x0 char}    {1x8 uint8}      8       {0x0 struct}    false    false 
    0.30459 sec      600     false      {0x0 char}    {1x6 uint8}      6       {0x0 struct}    false    false 

停止通道

使用 stop 命令将通道设置为离线状态。

stop(rxCh);

分析收到的报文

MATLAB® 为执行 CAN 报文分析提供功能强大的环境。plot 命令可以创建具有报文时间戳和标识符的散点图,以便概览某些报文何时出现在网络上。

plot(rxMsg.Time, rxMsg.ID, 'x')
ylim([0 2047])
xlabel('Timestamp')
ylabel('CAN Identifier')