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如何在Raspberry PI上设置串行端口的波特率?

  •  3
  • OlavT  · 技术社区  · 7 年前

    我有以下几点。NET Core 2.0 C代码:

    using System;
    using System.Runtime.InteropServices;
    
    namespace TestSerial
    {
        class Program
        {
            [Flags]
            public enum OpenFlags
            {
                O_RDONLY = 0,
                O_WRONLY = 1,
                O_RDWR = 2,
    
                O_NONBLOCK = 4,
            }
    
            [DllImport("libc")]
            public static extern int cfsetspeed(byte[] termios_data, long speed);
    
            [DllImport("libc")]
            public static extern int tcgetattr(int fd, [Out] byte[] termios_data);
    
            [DllImport("libc")]
            public static extern int tcsetattr(int fd, int optional_actions, byte[] termios_data);
    
            [DllImport("libc")]
            public static extern int open(string pathname, OpenFlags flags);
    
    
            static void Main(string[] args)
            {
                const string serialDevice = "/dev/serial/by-id/usb-ELT_SENSOR_EK100_V1.0_SN000001-if00-port0";
    
                int fileDescriptor = open(serialDevice, OpenFlags.O_RDONLY | OpenFlags.O_NONBLOCK);
                Console.WriteLine($"Libc.open returned {fileDescriptor}");
    
                byte[] termiosData = new byte[256];
    
                int result = tcgetattr(fileDescriptor, termiosData);
                Console.WriteLine($"Libc.tcgetattr returned {result}");
    
                result = cfsetspeed(termiosData, 38400);
                Console.WriteLine($"Libc.cfsetspeed returned {result}");
    
                result = tcsetattr(fileDescriptor, 0, termiosData);
                Console.WriteLine($"Libc.tcsetattr returned {result}");
            }
        }
    }
    

    程序应将USB串行端口的波特率更改为38400。但是,该程序并没有如预期的那样工作。

    这是运行程序的输出:

    Libc.open returned 18
    Libc.tcgetattr returned 0
    Libc.cfsetspeed returned -1
    Libc.tcsetattr returned 0
    

    我还仔细检查了串行端口设置,它确实没有改变:

    $ sudo stty -a -F /dev/serial/by-id/usb-ELT_SENSOR_EK100_V1.0_SN000001-if00-port0
    speed 9600 baud; rows 0; columns 0; line = 0;
    intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>;
    eol2 = <undef>; swtch = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R;
    werase = ^W; lnext = ^V; discard = ^O; min = 1; time = 0;
    -parenb -parodd -cmspar cs8 hupcl -cstopb cread clocal -crtscts
    -ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon -ixoff
    -iuclc -ixany -imaxbel -iutf8
    opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
    isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt
    echoctl echoke -flusho -extproc
    

    Libc返回错误的原因可能是什么。cfsetspeed(设置速度)?

    1 回复  |  直到 7 年前
        1
  •  0
  •   OlavT    7 年前

    问题是cfsetspeed函数的速度参数声明中的数据类型(长)不正确。速度参数的数据类型应为uint。

    这是正确的代码:

    using System;
    using System.Runtime.InteropServices;
    
    namespace TestSerial
    {
        class Program
        {
            [Flags]
            public enum OpenFlags
            {
                O_RDONLY = 0,
                O_WRONLY = 1,
                O_RDWR = 2,
    
                O_NONBLOCK = 4,
            }
    
            [DllImport("libc")]
            public static extern int cfsetspeed(byte[] termios_data, uint speed);
    
            [DllImport("libc")]
            public static extern int tcgetattr(int fd, [Out] byte[] termios_data);
    
            [DllImport("libc")]
            public static extern int tcsetattr(int fd, int optional_actions, byte[] termios_data);
    
            [DllImport("libc")]
            public static extern int open(string pathname, OpenFlags flags);
    
    
            static void Main(string[] args)
            {
                const string serialDevice = "/dev/serial/by-id/usb-ELT_SENSOR_EK100_V1.0_SN000001-if00-port0";
    
                int fileDescriptor = open(serialDevice, OpenFlags.O_RDONLY | OpenFlags.O_NONBLOCK);
                Console.WriteLine($"Libc.open returned {fileDescriptor}");
    
                byte[] termiosData = new byte[256];
    
                int result = tcgetattr(fileDescriptor, termiosData);
                Console.WriteLine($"Libc.tcgetattr returned {result}");
    
                result = cfsetspeed(termiosData, 38400);
                Console.WriteLine($"Libc.cfsetspeed returned {result}");
    
                result = tcsetattr(fileDescriptor, 0, termiosData);
                Console.WriteLine($"Libc.tcsetattr returned {result}");
            }
        }
    }