从秤到 PC 的串行到 USB 电缆，一些值只是问号

Question

我正在尝试编写一个程序来使用串行到 USB 转换器电缆从旧的 AND 秤读取数据以显示在文本框中。我能够成功编写一个程序来仅从 RS232 串行电缆读取数据，但是当我将串口连接到 USB 电缆时，它只显示一些数字，其他的只是问号。（例如：???0.3?2?）

我用来读取数据的方法。

 private void PortOnDataReceived(object sender, SerialDataReceivedEventArgs e)
    {
        while (_port.BytesToRead > 0)
        {
            // PostKeys
            var original = _port.ReadExisting();
         
            // Reformat string to fit SendKeys()
            var reformattedString = DefaultFormatter.Reformat(original);
            try
            {
                SendKeys.SendWait(reformattedString);
            }
            // Handle exception caused if keys are sent to an application
            // not handling keys
            catch(Exception ex)    
            {
            }
        }
    }

这是我可以通过代码解决的问题还是串口转 USB 电缆出现故障？

Answer 1

我用 USB 串口设备测试了下面的代码，它可能也适用于您的体重秤。 downloading/installing WinCT (RsCom, RsKey & RsWeight)) 发现了一些端口设置。然后，在 A&D WinCT 下的 Windows 开始菜单中，select RsCom 或 RsKey。使用 RsCom 或 RsKey 是检查 USB cable/connection 是否正常工作的简单方法。我在我的 USB 串行设备上同时使用了“RsKey”和“RsCom”，它似乎工作正常。

创建 WinForms 项目

VS 2017:

打开Visual Studio
展开已安装
展开Visual C#
单击Windows桌面
Select Windows 表单应用程序 (.NET Framework)
指定项目名称（名称：ReadSerialPort）
单击确定

VS 2019:

打开Visual Studio
单击继续，无需代码
单击文件
Select 新建
Select 项目
C# Windows 桌面
单击 Windows 表单应用程序 (.NET Framework)
点击下一步
指定项目名称（名称：ReadSerialPort）
单击创建

注意：从现在开始，VS 2017 和 VS 2019 的过程相同。

添加class：SerialPortDataReceivedEventArgs

注意：此class将与将从串行端口设备接收到的数据发送到订阅者的事件一起使用。

在 VS 菜单上，select 项目
Select添加Class（名称：SerialPortDataReceivedEventArgs.cs）

SerialPortDataReceivedEventArgs.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ReadSerialPort
{
    public delegate void SerialPortDataReceivedEventHandler(object sender, SerialPortDataReceivedEventArgs e);

    public class SerialPortDataReceivedEventArgs : System.EventArgs
    {
        public string Data { get; private set; } = string.Empty;

        public SerialPortDataReceivedEventArgs(string data)
        {
            this.Data = data;
        }
    }
}

添加对 System.Management

的引用

在 VS 菜单中，select 项目
Select 添加引用
展开程序集
勾选System.Management
单击确定

添加class: ComPorts

在 VS 菜单上，select 项目
Select添加Class（名称：ComPorts.cs）

ComPorts.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ReadSerialPort
{
    public class ComPorts
    {
        public List<ComPortInfo> Ports { get; set; } = new List<ComPortInfo>();
    }

    public class ComPortInfo
    {
        public string Name { get; set; }
        public string PortName { get; set; }

        public ComPortInfo()
        {

        }

        public ComPortInfo(string name, string portName)
        {
            this.Name = name;
            this.PortName = portName;
        }
    }
}

添加class:HelperSerialPort

在 VS 菜单上，select 项目
Select添加Class（名称：HelperSerialPort.cs）

HelperSerialPort.cs

//if using .NET 5, install NuGet Package: System.IO.Ports

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO.Ports;
using System.Diagnostics;
using System.Management;

namespace ReadSerialPort
{
    public enum PortBaudRate : int
    {
        Baud1200 = 1200,
        Baud2400 = 2400,
        Baud4800 = 4800,
        Baud9600 = 9600,
        Baud14400 = 14400,
        Baud19200 = 19200,
        Baud28800 = 28800,
        Baud38400 = 38400
    };

    public class HelperSerialPort : IDisposable
    {
        public delegate void SerialPortErrorReceivedEventHandler(object sender, SerialErrorReceivedEventArgs e);

        public event SerialPortDataReceivedEventHandler DataReceived;
        public event SerialPortErrorReceivedEventHandler ErrorReceived;

        private string _dataReceived = string.Empty;
        public System.IO.Ports.SerialPort Port { get; private set; }

        public HelperSerialPort()
        {
            //create new instance
            Port = new SerialPort();
        }

        public string Connect(string comPort, PortBaudRate baudRate = PortBaudRate.Baud9600)
        {
            string portName = string.Empty;
            string result = string.Empty;

            if (String.IsNullOrEmpty(comPort))
            {
                System.Windows.Forms.MessageBox.Show("COM port not selected.", "Error - COM Port", System.Windows.Forms.MessageBoxButtons.OK, System.Windows.Forms.MessageBoxIcon.Error);
                return "Error: COM port not selected.";
            }

            try
            {
                if (Port == null)
                {
                    //create new instance
                    Port = new SerialPort();
                }

                if (!Port.IsOpen)
                {
                    Debug.WriteLine("opening port");

                    //create new instance
                    Port = new SerialPort(comPort);

                    //set properties
                    Port.BaudRate = (int)baudRate;
                    Port.Handshake = Handshake.None;
                    Port.Parity = Parity.Even; //Even,None,Odd supported
                    Port.DataBits = 7;
                    Port.StopBits = StopBits.One;
                    Port.ReadTimeout = 200;
                    Port.WriteTimeout = 50;
                    Port.DtrEnable = true; //enable Data Terminal Ready
                    Port.RtsEnable = true; //enable Request to send

                    //open port
                    Port.Open();

                    //subscribe to events 
                    Port.DataReceived += Port_DataReceived;
                    Port.ErrorReceived += Port_ErrorReceived;

                    //set value
                    result = "Connected";
                }
                else
                {
                    Debug.WriteLine("else");
                }
            }
            catch(Exception ex)
            {
                result = "Error: (Connect) - " + ex.Message;
            }

            Debug.WriteLine("result: " + result);
            
            return result;
        }


        public void Close()
        {
            Dispose();
        }
        
        public void Dispose()
        {
            if (Port != null)
            {
                if (Port.IsOpen)
                {
                    Port.Close();
                }

                //unsubscribe from events
                Port.DataReceived -= Port_DataReceived;
                Port.ErrorReceived -= Port_ErrorReceived;

                Port.Dispose();

                Port = null;
            }
        }

       
        public ComPorts GetComPortInfo()
        {
            ComPorts comPorts = new ComPorts();

            SortedDictionary<string, string> comPortNameDict = new SortedDictionary<string, string>();
            SortedDictionary<string, string> portDict = new SortedDictionary<string, string>();

            string[] portNames = SerialPort.GetPortNames();

            //get USB COM ports
            using (var searcher = new ManagementObjectSearcher("SELECT * FROM WIN32_PnPEntity"))
            {
                ManagementObjectCollection pnpEntityItems = searcher.Get();

                if (portNames != null && pnpEntityItems != null)
                {
                    var props = pnpEntityItems.GetEnumerator();

                    foreach (ManagementBaseObject mbo in pnpEntityItems)
                    {
                        if (mbo != null)
                        {
                            object nameObj = mbo.GetPropertyValue("Name");
                            object pnpClassObj = mbo.GetPropertyValue("PNPClass");

                            if (nameObj != null && pnpClassObj != null)
                            {
                                if (pnpClassObj.ToString() == "Ports" && nameObj.ToString().ToLower().Contains("(com"))
                                {
                                    string name = mbo.GetPropertyValue("Name").ToString().Trim();
                                    //Debug.WriteLine("name: " + name);

                                    string portName = string.Empty;

                                    if (name.Contains("(") && name.Contains(")"))
                                    {
                                        portName = name.Substring(name.IndexOf("(") + 1, name.IndexOf(")") - name.IndexOf("(") - 1);
                                        //Debug.WriteLine("Port Name: '" + portName + "'");
                                    }

                                    if (!portDict.ContainsKey(name))
                                    {
                                        //add to dictionary - ex: Voyager 1450g, COM1
                                        portDict.Add(name, portName);

                                        //add to dictionary - ex: COM1, Voyager 1450g
                                        comPortNameDict.Add(portName, name);
                                    }
                                }
                            }
                        }
                    }
                }
            }

            //add any ports that aren't USB -- ie: RS-232 (serial) devices
            //USB devices are already in the dictionary, so only add devices 
            //that don't already exist in the dictionary
            if (portNames != null && portDict != null && comPortNameDict != null)
            {
                foreach (string name in portNames)
                {
                    if (!comPortNameDict.ContainsKey(name))
                    {
                        //add to dictionary
                        portDict.Add(name, name);
                    }
                }
            }

            foreach(KeyValuePair<string, string> kvp in portDict)
            {
                //add to list
                comPorts.Ports.Add(new ComPortInfo(kvp.Key, kvp.Value));
            }

            return comPorts;
        }

        private void Port_ErrorReceived(object sender, SerialErrorReceivedEventArgs e)
        {
            Debug.WriteLine("Error: (sp_ErrorReceived) - " + e.EventType);

            if (this.ErrorReceived != null)
            {
                ErrorReceived(this, e);
            }
        }

        private void Port_DataReceived(object sender, SerialDataReceivedEventArgs e)
        {
            _dataReceived = Port.ReadExisting();

            Debug.WriteLine("_dataReceived: " + _dataReceived);

            if (this.DataReceived != null)
            {
                SerialPortDataReceivedEventArgs eventArgs = new SerialPortDataReceivedEventArgs(_dataReceived);
                DataReceived(this, eventArgs);
            }
        }

        public void SerialCmdSend(string data)
        {
            if (Port.IsOpen)
            {
                try
                {
                    // Send the binary data out the port
                    byte[] hexstring = Encoding.ASCII.GetBytes(data);

                    //write to SerialPort
                    foreach (byte hexval in hexstring)
                    {
                        byte[] _hexval = new byte[] { hexval }; // need to convert byte to byte[] to write
                        Port.Write(_hexval, 0, 1);
                        System.Threading.Thread.Sleep(1);
                    }
                }
                catch (Exception ex)
                {
                    Debug.WriteLine("Error: Failed to SEND" + data + "\n" + ex.Message + "\n");
                }
            }
            else
            {
                Debug.WriteLine("Error: Port is not open. Please open the connection and try again.");
            }
        }
    }
}

注意：您可能需要安装 USB 驱动程序。 AND Driver Software.

创建可与 RichTextBox 一起使用的扩展方法。

创建 class (ControlExtensions)

见How to update a RichTextBox from BackgroundWorker using BeginInvoke

在 VS 菜单上，select 项目
Select添加Class（名称：ControlExtensions.cs）

ControlExtensions.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace ReadSerialPort
{
    public static class ControlExtensions
    {
        public static void Invoke(this Control control, Action action)
        {
            if (control.InvokeRequired) control.Invoke(new MethodInvoker(action), null);
            else action.Invoke();
        }
    }
}

接下来我们将向 Form1 添加一些控件和代码。

打开属性 Window

在VS菜单中，select 查看
Select属性Window

打开解决方案资源管理器

在VS菜单中，select 查看
Select 解决方案资源管理器
在解决方案资源管理器中，双击 Form1.cs 打开设计器。

将“连接”按钮添加到 Form1

在VS菜单中，select 查看
Select 工具箱
Select 按钮
单击 Form1 将按钮添加到表单
在属性 Window 中，为“button1”设置 (name): btnConnect；设置文本：连接
在属性 Window 中，单击（事件）。双击单击将事件处理程序添加到Form1.cs

向 Form1 添加“断开连接”按钮

在VS菜单中，select 查看
Select 工具箱
Select 按钮
单击 Form1 将按钮添加到表单
在属性 Window 中，为“button1”设置 (name): btnDisconnect；设置文本：断开连接
在属性 Window 中，单击（事件）。双击单击将事件处理程序添加到Form1.cs

将 RichTextBox 添加到 Form1

在VS菜单中，select 查看
Select 工具箱
Select RichTextBox
单击 Form1 将按钮添加到表单
在属性 Window 中，为“richTextBox1”设置 (name): richTextBoxReceivedData

将“加载”事件处理程序添加到 Form1

在属性 Window 中，对于“Form1”，单击（事件）。双击 Load 以将事件处理程序添加到 Form1.cs

将“FormClosing”事件处理程序添加到 Form1

在属性 Window 中，对于“Form1”，单击（事件）。双击 FormClosing 以将事件处理程序添加到 Form1.cs

修改Form1.cs代码

在解决方案资源管理器中，右键单击 Form1.cs
Select 查看代码

选项 1（插入 USB 设备时不自动检测 in/unplugged）：

Form1.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Diagnostics;

namespace ReadSerialPort
{
    public partial class Form1 : Form
    {
        private HelperSerialPort helperSerialPort = new HelperSerialPort();
        private ComPorts comPorts = null;

        public Form1()
        {
            InitializeComponent();
        }

        private void FrmMain_Load(object sender, EventArgs e)
        {
            //get COM port info
            GetComPorts();
        }

        private void HelperSerialPort_DataReceived(object sender, SerialPortDataReceivedEventArgs e)
        {
            Debug.WriteLine("Data: " + e.Data);

            richTextBoxReceivedData.Invoke(() =>
            {
                richTextBoxReceivedData.AppendText(e.Data);
                richTextBoxReceivedData.Refresh();
            });
        }

        private void btnConnect_Click(object sender, EventArgs e)
        {
            if (helperSerialPort.Port == null || !helperSerialPort.Port.IsOpen)
            {
                helperSerialPort.Connect("COM3", PortBaudRate.Baud9600);

                helperSerialPort.DataReceived += HelperSerialPort_DataReceived;
            }

        }
        private void btnDisconnect_Click(object sender, EventArgs e)
        {
            helperSerialPort.Dispose();
        }

        private void FrmMain_FormClosing(object sender, FormClosingEventArgs e)
        {
            if (helperSerialPort != null && helperSerialPort.Port != null)
            {
                helperSerialPort.Dispose();
                helperSerialPort = null;
            }
        }

        private void GetComPorts()
        {
            //get COM port info
            comPorts = helperSerialPort.GetComPortInfo();

            foreach (ComPortInfo cpInfo in comPorts.Ports)
            {
                Debug.WriteLine("Name: '" + cpInfo.Name + "' PortName: '" + cpInfo.PortName + "'");
            }
        }
    }
}

选项2（插入USB设备时自动检测in/unplugged）：

注：以下部分代码来自：Check for device change (add/remove) events

创建class (UsbDeviceNotification)

在 VS 菜单上，select 项目
Select添加Class（名称：UsbDeviceNotification.cs）

UsbDeviceNotification.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Runtime.InteropServices;

namespace ReadSerialPort
{
    public static class UsbDeviceNotification
    {
        public const int DbtDevicearrival = 0x8000; // system detected a new device        
        public const int DbtDeviceremovecomplete = 0x8004; // device is gone      
        public const int WmDevicechange = 0x0219; // device change event      
        private const int DbtDevtypDeviceinterface = 5;
        private static readonly Guid GuidDevinterfaceUSBDevice = new Guid("A5DCBF10-6530-11D2-901F-00C04FB951ED"); // USB devices
        private static IntPtr notificationHandle;

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr RegisterDeviceNotification(IntPtr recipient, IntPtr notificationFilter, int flags);

        [DllImport("user32.dll")]
        private static extern bool UnregisterDeviceNotification(IntPtr handle);

        [StructLayout(LayoutKind.Sequential)]
        private struct DevBroadcastDeviceinterface
        {
            internal int Size;
            internal int DeviceType;
            internal int Reserved;
            internal Guid ClassGuid;
            internal short Name;
        }

        /// <summary>
        /// Registers a window to receive notifications when USB devices are plugged or unplugged.
        /// </summary>
        /// <param name="windowHandle">Handle to the window receiving notifications.</param>
        public static void RegisterUsbDeviceNotification(IntPtr windowHandle)
        {
            DevBroadcastDeviceinterface dbi = new DevBroadcastDeviceinterface
            {
                DeviceType = DbtDevtypDeviceinterface,
                Reserved = 0,
                ClassGuid = GuidDevinterfaceUSBDevice,
                Name = 0
            };

            dbi.Size = Marshal.SizeOf(dbi);
            IntPtr buffer = Marshal.AllocHGlobal(dbi.Size);
            Marshal.StructureToPtr(dbi, buffer, true);

            notificationHandle = RegisterDeviceNotification(windowHandle, buffer, 0);
        }

        /// <summary>
        /// Unregisters the window for USB device notifications
        /// </summary>
        public static void UnregisterUsbDeviceNotification()
        {
            UnregisterDeviceNotification(notificationHandle);
        }

    }
}

然后在Form1.cs中使用如下代码：

Form1.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Diagnostics;

namespace ReadSerialPort
{
    public partial class Form1 : Form
    {
        private HelperSerialPort helperSerialPort = new HelperSerialPort();
        private ComPorts comPorts = null; 

        public Form1()
        {
            InitializeComponent();
        }

        private void FrmMain_Load(object sender, EventArgs e)
        {
            //get COM port info
            GetComPorts();
        }

        private void HelperSerialPort_DataReceived(object sender, SerialPortDataReceivedEventArgs e)
        {
            Debug.WriteLine("Data: " + e.Data);

            richTextBoxReceivedData.Invoke(() =>
            {
                richTextBoxReceivedData.AppendText(e.Data);
                richTextBoxReceivedData.Refresh();
            });
        }

        private void btnConnect_Click(object sender, EventArgs e)
        {
            if (helperSerialPort.Port == null || !helperSerialPort.Port.IsOpen)
            {
                helperSerialPort.Connect("COM3", PortBaudRate.Baud9600);

                helperSerialPort.DataReceived += HelperSerialPort_DataReceived;
            }

        }
        private void btnDisconnect_Click(object sender, EventArgs e)
        {
            helperSerialPort.Dispose();
        }

        private void FrmMain_FormClosing(object sender, FormClosingEventArgs e)
        {
            if (helperSerialPort != null && helperSerialPort.Port != null)
            {
                helperSerialPort.Dispose();
                helperSerialPort = null;
            }
        }

        private void GetComPorts()
        {
            //use SynchronizationContext.Current with ThreadPool to avoid the following error:
            //Transition into COM context...for this RuntimeCallableWrapper failed with the following error: 
            //An outgoing call cannot be made since the application is dispatching an input-synchronous call. 
            //Exception from HRESULT: 0x8001010D (RPC_E_CANTCALLOUT_INPUTSYNCCALL)

            var sc = System.Threading.SynchronizationContext.Current;
            System.Threading.ThreadPool.QueueUserWorkItem(delegate
            {
                //do work on threadpool
                sc.Post(delegate
                {
                    //get COM port info
                    comPorts = helperSerialPort.GetComPortInfo();

                    foreach (ComPortInfo cpInfo in comPorts.Ports)
                    {
                        Debug.WriteLine("Name: '" + cpInfo.Name + "' PortName: '" + cpInfo.PortName + "'");
                    }
                }, null);
            });

        }

        private void UsbDeviceAdded()
        {
            //ToDo: add desired code

            Debug.WriteLine("Info: USB device added");


            //get COM port info
            GetComPorts();
        }

        private void UsbDeviceRemoved()
        {
            //ToDo: add desired code

            Debug.WriteLine("Info: USB device removed");

            //get COM port info
            GetComPorts();

        }
        protected override void WndProc(ref Message m)
        {
            base.WndProc(ref m);
            if (m.Msg == UsbDeviceNotification.WmDevicechange)
            {
                switch ((int)m.WParam)
                {
                    case UsbDeviceNotification.DbtDeviceremovecomplete:
                        UsbDeviceRemoved();
                        break;
                    case UsbDeviceNotification.DbtDevicearrival:
                        UsbDeviceAdded();
                        break;
                }
            }
        }
    }
}

从秤到 PC 的串行到 USB 电缆，一些值只是问号

Serial to USB cable from a scale to PC ,some values are just question marks

c#

usb

serial-port

usbserial