python-can 的使用

• 最近在搞 websocket, 服務端是用 python 寫的，所以，我需要用python 控制 can 去傳輸相關信息。

• python-can 模塊就是 python 控制 can 的模仿。

• 利用 buildroot 去生成 python-can 模塊

    cd  $BUILDROOT_PATH
    make menuconfig 
    Target packages  --->
        Interpreter languages and scripting  --->
            [*] python3
                External python modules  --->
                    [*] python-can 

    make 
    // 生成的文件在   output/target/usr/lib/python3.5/site-packages/
    //  將這個文件 拷貝到自己的文件系統的 ust/lib/python3.5 里面

• python-can 文檔地址：

    https://python-can.readthedocs.io/en/latest/index.html#

• python-can 的使用

    #!/usr/bin/python3
  
    import os;    '''  這是加載 os 模塊， 調用shell 命令 '''
    import can;      '''  加載python-can 模塊 '''

    can.rc['interface'] = 'socketcan_native'   ```  Linux 里面的 socketcan 在am335x 上面應該使用這個 ```
    can.rc['channel'] = 'can1'                  ''' can 接口名字  '''
    can.rc['bitrate'] = 1000000                ''' 波特率       1M '''
    from can.interfaces.interface import Bus
    '''  這個函數是can 的啟動函數 '''
    def can_setup(can_name):
        can_setup_command = "canconfig " + can_name + " bitrate 1000000 restart-ms 1000 ctrlmode triple-sampling on";
        can_start_command = "canconfig " + can_name + " start";
        pass;
        os.system(can_setup_command);
        os.system(can_start_command);
    '''  can 停止函數  '''
    def can_stop(can_name):
        can_stop_command = "canconfig " + can_name + " stop";
        os.system(can_stop_command);
    '''   發送信息 '''
    def send_one():
        bus = can.interface.Bus();
        msg = can.Message(arbitration_id=0x7f,
                data=[11, 25, 11, 1, 1, 2, 23, 18], 
                extended_id=False);
        try:
            bus.send(msg);   ''' 發送信息 '''
            print("Message sent on {}".format(bus.channel_info));
        except can.CanError:
            print("Message NOT sent");
        
    def recv():
        bus = can.interface.Bus();
        msg = bus.recv(100);   ''' 接收信息 '''
        try:
            bus.send(msg);
            print(msg);
            print(msg.data[0]);              #  接收回來的第一個字節的數據
            print(msg.arbitration_id);    # 接收回來的ID
            return msg;
        except can.CanError:
            print("Message NOT sent");

    if __name__ == "__main__":
        '''   can_setup("can1"); '''
        send_one();
        recv();
        ''' can_stop("can1"); '''