c# - 如何在Raspberry PI的串行端口上设置波特率？

我有以下.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}");
        }
    }
}

该程序应将USB串行端口的波特率更改为38400。但是，该程序无法正常工作。

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，确实没有更改：

$ 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;
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-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.cfsetspeed返回的错误可能是什么原因？

最佳答案

问题是cfsetspeed函数的speed参数的声明中的数据类型不正确（长）。 speed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}");
        }
    }
}

关于c# - 如何在Raspberry PI的串行端口上设置波特率？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/47912133/