C# 编写 自动识别串口是否被占用，不占用打开串口，读取串口指定字符串，把字符串写入excel保存，然后关闭串口等待30S重复上面操作

以下是C#代码示例，可以实现你的需求：

using System;
using System.IO.Ports;
using System.Threading;
using System.IO;
using Excel = Microsoft.Office.Interop.Excel;

namespace SerialPortReadWrite
{
    class Program
    {
        static SerialPort _serialPort;
        static Excel.Application _excelApp;

        static void Main(string[] args)
        {
            _serialPort = new SerialPort("COM1", 9600, Parity.None, 8, StopBits.One);

            while (true)
            {
                if (!_serialPort.IsOpen)
                {
                    try
                    {
                        _serialPort.Open();
                        Console.WriteLine("串口已打开");
                    }
                    catch (Exception ex)
                    {
                        Console.WriteLine($"串口打开失败：{ex.Message}");
                        Thread.Sleep(30000);
                        continue;
                    }
                }

                bool isReadSuccessful = false;
                string readString = string.Empty;

                try
                {
                    readString = _serialPort.ReadLine();
                    isReadSuccessful = true;
                    Console.WriteLine($"读取到的字符串：{readString}");
                }
                catch (TimeoutException)
                {
                    Console.WriteLine("读取超时");
                }
                catch (Exception ex)
                {
                    Console.WriteLine($"读取串口失败：{ex.Message}");
                }

                if (isReadSuccessful)
                {
                    try
                    {
                        _excelApp = new Excel.Application();
                        Excel.Workbook workbook = _excelApp.Workbooks.Open("test.xlsx");
                        Excel.Worksheet worksheet = (Excel.Worksheet)workbook.Worksheets[1];
                        worksheet.Cells[1, 1] = readString;
                        workbook.Save();
                        workbook.Close();
                        _excelApp.Quit();
                        Console.WriteLine("写入Excel成功");
                    }
                    catch (Exception ex)
                    {
                        Console.WriteLine($"写入Excel失败：{ex.Message}");
                    }
                }

                _serialPort.Close();
                Console.WriteLine("串口已关闭");
                Thread.Sleep(30000);
            }
        }
    }
}

代码中使用了`SerialPort`类来操作串口，使用`Excel`类库来操作Excel文件，使用`Thread`类来实现等待30秒的功能。首先判断串口是否被占用，如果没有被占用则打开串口，然后读取串口数据并写入Excel文件，最后关闭串口并等待30秒后重复上述操作。需要注意的是，代码中的串口号和波特率需要根据具体的设备进行修改。