问题描述
我是一个手持复制粘贴的新手，试图从旧的Avery-Weightronix 7820秤中获取数据。我通过RJ-232电缆将其连接起来，并设法从秤上获得响应。我按照本教程https://www.studentcompanion.co.za/creating-a-serial-port-interface-with-c/进行了设置并开始运行。
一旦我开始使用它，我想简化它，并实质上将计算机用作远程显示器。我对串行连接参数进行了硬编码，并设置了代码以每秒发送一次重量请求，以便可以在winform中显示它。
稍后，我计划扩展它，以便获得多个项目的总重量。我计划称量一个项目，将重量复制到一个总计中，在秤上放一个新项目，然后重复。
我之所以陷入困境，是因为我无法始终如一地解析从秤返回的数据，并且因为循环锁定了UI。
当我发送W <CR>这是当前重量的请求时，示例响应为：
<LF> 0001.10lb <CR> <LF> 00 <CR><ETX>
<ETX> =文本结尾字符（Ø3十六进制），<LF> =换行符（ØA十六进制），<CR> =回车符（ØD十六进制）。
秤的响应是固定长度的，但是当我进入调试模式时，在代码的前几个周期中未收到响应。然后它到达以后。将其输出到RTF格式时可以，但是当我尝试提取子字符串时，如果没有数据，则会出现错误。
此外，UI锁定，我唯一能做的就是停止执行。通过阅读，看来我应该实现线程，但是我不确定如何重新组织代码来实现这一点。
对于如何解决这些问题，我将不胜感激。
这是我的代码：
using System;
using System.Drawing;
using System.Windows.Forms;
using System.IO.Ports;
namespace ScaleView
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void groupBox1_Enter(object sender,EventArgs e)
{
}
private void Form1_Load(object sender,EventArgs e)
{
//updatePorts(); //Call this function everytime the page load
//to update port names
CheckForIllegalCrossthreadCalls = false;
}
private SerialPort ComPort = new SerialPort(); //Initialise ComPort Variable as SerialPort
private void connect()
{
bool error = false;
ComPort.PortName = "COM3";
ComPort.Baudrate = int.Parse("9600"); //convert Text to Integer
ComPort.Parity = (Parity)Enum.Parse(typeof(Parity),"Even"); //convert Text to Parity
ComPort.DataBits = int.Parse("7"); //convert Text to Integer
ComPort.StopBits = (StopBits)Enum.Parse(typeof(StopBits),"1"); //convert Text to stop bits
try //always try to use this try and catch method to open your port.
//if there is an error your program will not display a message instead of freezing.
{
//Open Port
ComPort.open();
ComPort.DataReceived += SerialPortDataReceived; //Check for received data. When there is data in the receive buffer,//it will raise this event,we need to subscribe to it to kNow when there is data
//MessageBox.Show(this,"Connected",MessageBoxButtons.OK);
}
catch (UnauthorizedAccessException) { error = true; }
catch (System.IO.IOException) { error = true; }
catch (ArgumentException) { error = true; }
if (error) MessageBox.Show(this,"Could not open the COM port. Most likely it is already in use,has been removed,or is unavailable.","COM Port unavailable",MessageBoxButtons.OK,MessageBoxIcon.Stop);
//if the port is open,Change the Connect button to disconnect,enable the send button.
//and disable the groupBox to prevent changing configuration of an open port.
if (ComPort.IsOpen)
{
btnConnect.Text = "disconnect";
}
}
// Call this function to close the port.
private void disconnect()
{
ComPort.Close();
btnConnect.Text = "Connect";
}
//whenever the connect button is clicked,it will check if the port is already open,call the disconnect function.
// if the port is closed,call the connect function.
private void btnConnect_Click_1(object sender,EventArgs e)
{
if (ComPort.IsOpen)
{
disconnect();
}
else
{
connect();
rtxtDataArea.AppendText("Connected\n");
sendData();
}
}
private void btnClear_Click(object sender,EventArgs e)
{
//Clear the screen
rtxtDataArea.Clear();
}
// Function to send data to the serial port
private void sendData()
{
bool error = false;
while(ComPort.IsOpen) //if text mode is selected,send data as tex
{
try
{
// Convert string of hex digits (in this case representing W<CR>) to a byte array
string hextext = "57 0D";
byte[] data = HexStringToByteArray(hextext);
// Send the binary data out the port
ComPort.Write(data,data.Length);
System.Threading.Thread.Sleep(3000);
rtxtDataArea.ForeColor = Color.Blue; //write Hex data in Blue
string response = ComPort.ReadLine();
int charfrom = 1;
int charto = 9;
//string weight = response.Substring(charfrom,charto - charfrom);
rtxtDataArea.AppendText(response + "TEST\n");
}
catch (FormatException) { error = true; }
// Inform the user if the hex string was not properly formatted
catch (ArgumentException) { error = true; }
if (error) MessageBox.Show(this,"Not properly formatted hex string: \n" + "example: E1 FF 1B","Format Error",MessageBoxIcon.Stop);
}
}
//Convert a string of hex digits (example: E1 FF 1B) to a byte array.
//The string containing the hex digits (with or without spaces)
//Returns an array of bytes. </returns>
private byte[] HexStringToByteArray(string s)
{
s = s.Replace(" ","");
byte[] buffer = new byte[s.Length / 2];
for (int i = 0; i < s.Length; i += 2)
buffer[i / 2] = (byte)Convert.ToByte(s.Substring(i,2),16);
return buffer;
}
private void btnSend_Click(object sender,EventArgs e)
{
sendData();
}
//This event will be raised when the form is closing.
private void Form1_FormClosing(object sender,FormClosingEventArgs e)
{
if (ComPort.IsOpen) ComPort.Close(); //close the port if open when exiting the application.
}
//Data recived from the serial port is coming from another thread context than the UI thread.
//Instead of reading the content directly in the SerialPortDataReceived,we need to use a delegate.
delegate void SetTextCallback(string text);
private void SetText(string text)
{
//invokerequired required compares the thread ID of the calling thread to the thread of the creating thread.
// if these threads are different,it returns true
if (this.rtxtDataArea.Invokerequired)
{
rtxtDataArea.ForeColor = Color.Green; //write text data in Green colour
SetTextCallback d = new SetTextCallback(SetText);
this.Invoke(d,new object[] { text });
}
else
{
this.rtxtDataArea.AppendText(text);
}
}
private void SerialPortDataReceived(object sender,SerialDataReceivedEventArgs e)
{
var serialPort = (SerialPort)sender;
var data = serialPort.ReadExisting();
SetText(data);
}
private void rtxtDataArea_TextChanged(object sender,EventArgs e)
{
}
}
}
解决方法
同时删除oui和try-catch方法中的MessageBox.Show(...)块和connect()。 sendData()块中的try-catch将捕获所有异常并将其发送到UI线程。
删除new Thread(() => {行，因为它绕过了内置保护。 CheckForIllegalCrossThreadCalls = false;方法可能比serialPort.ReadLine();更好，因为serialPort.ReadExisting();将等待一整行数据。
这应该使您对代码的外观有所了解：
ReadLine()