通过P/Invoke控制继电器

关于P/Invoke不用多说，主要用途就是通过托管程序（比如C#）调用非托管程序（比如C++），这个技术主要用在通过C#控制硬件等操作。主要注意点就是要看C++函数原型以及参数说明，将C++参数类型转换为对应的C#参数类型，所以要求熟悉基本的C++程序。

这里提供一个通过C#控制电磁继电器的程序片段，以供参考。

功能截图：

打开时，继电器上的小灯会亮起来；关闭时，继电器上的小灯会灭掉。

代码片段：

namespace 电磁继电器2
{
    public partial class Form1 : Form
    {
        private IntPtr intPtr;
        private usb_relay_device_info device;
        private int deviceNum;

        public Form1()
        {
            InitializeComponent();
        }

        [StructLayout(LayoutKind.Sequential)]
        public struct usb_relay_device_info
        {
            [MarshalAs(UnmanagedType.LPStr)]
            public string serial_number;
            [MarshalAs(UnmanagedType.LPStr)]
            public string device_path;
            public usb_relay_device_type type;
            public IntPtr next;
        }

        public enum usb_relay_device_type
        {
            USB_RELAY_DEVICE_ONE_CHANNEL = 1,
            USB_RELAY_DEVICE_TWO_CHANNEL = 2,
            USB_RELAY_DEVICE_FOUR_CHANNEL = 4,
            USB_RELAY_DEVICE_EIGHT_CHANNEL = 8
        }

        [DllImport("usb_relay_device.dll")]
        public static extern int usb_relay_init();//函数初始化

        [DllImport("usb_relay_device.dll")]
        public static extern IntPtr usb_relay_device_enumerate();//查找插入到电脑中的所有USB免驱继电器模块

        [DllImport("usb_relay_device.dll", CallingConvention = CallingConvention.Cdecl)]
        public static extern int usb_relay_device_open(IntPtr intPtr);//打开你需要操作的设备

        [DllImport("usb_relay_device.dll", CallingConvention = CallingConvention.Cdecl)]
        public static extern int usb_relay_device_open_with_serial_number(string serialNum, int length);//打开指定序列号的设备

        [DllImport("usb_relay_device.dll", CallingConvention = CallingConvention.Cdecl)]
        public static extern int usb_relay_device_open_one_relay_channel(int device, int index);//可以打开某路继电器

        [DllImport("usb_relay_device.dll", CallingConvention = CallingConvention.Cdecl)]
        public static extern int usb_relay_device_close_one_relay_channel(int device, int index);//可以关闭某路继电器

        [DllImport("usb_relay_device.dll", CallingConvention = CallingConvention.Cdecl)]
        public static extern int usb_relay_device_open_all_relay_channel(int deviceNum);//可以打开所有继电器

        [DllImport("usb_relay_device.dll", CallingConvention = CallingConvention.Cdecl)]
        public static extern int usb_relay_device_close_all_relay_channel(int deviceNum);//可以关闭所有继电器

        [DllImport("usb_relay_device.dll", CallingConvention = CallingConvention.Cdecl)]
        public static extern void usb_relay_device_free_enumerate(IntPtr intPtr);// 释放内存

        [DllImport("usb_relay_device.dll", CallingConvention = CallingConvention.Cdecl)]
        public static extern int usb_relay_exit();//释放内存

        private void button1_Click(object sender, EventArgs e)
        {
            int flag = usb_relay_init();//返回0 表示初始化ok
            intPtr = usb_relay_device_enumerate();
            object obj = Marshal.PtrToStructure(intPtr, typeof(usb_relay_device_info));
            device = ((usb_relay_device_info)obj);
            this.comboBox1.Items.Add(device.serial_number);
        }

        private void button2_Click(object sender, EventArgs e)
        {
            //两种方式均可打开设备

            //1.根据指针句柄打开设备
            //deviceNum = usb_relay_device_open(intPtr); 

            //2. 根据设备序列号打开设备
            deviceNum = usb_relay_device_open_with_serial_number(device.serial_number, device.serial_number.Length);

            this.pictureBox1.BackColor = Color.Green;
        }

        //1 开
        private void button3_Click(object sender, EventArgs e)
        {
            int flag = usb_relay_device_open_one_relay_channel(deviceNum, 1);
        }

        //1 关
        private void button4_Click(object sender, EventArgs e)
        {
            int flag = usb_relay_device_close_one_relay_channel(deviceNum, 1);
        }

        //2 开
        private void button6_Click(object sender, EventArgs e)
        {
            int flag = usb_relay_device_open_one_relay_channel(deviceNum, 2);
        }

        //2 关
        private void button5_Click(object sender, EventArgs e)
        {
            int flag = usb_relay_device_close_one_relay_channel(deviceNum, 2);
        }

        private void button7_Click(object sender, EventArgs e)
        {
            int flag = usb_relay_device_open_all_relay_channel(deviceNum);
        }

        private void button8_Click(object sender, EventArgs e)
        {
            int flag = usb_relay_device_close_all_relay_channel(deviceNum);
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            usb_relay_device_free_enumerate(intPtr);
            int flag = usb_relay_exit();
        }
    }
}