Question

我正在制作一个可以通过C＃控制Arduino板的程序。以下是该计划需要采取的步骤：

扫描COM端口
接收来自设备的输入
当输入具有特定短语，例如＆＃34; connectAlready＆＃34;，
关闭所有端口并在收到短语的端口上创建一个新端口。
现在程序知道Arduino所在的COM端口，它可以继续执行任务并通过SerialPorts发送命令。

以下是我目前为connect（）方法编写的代码。

public void connect()
    {
        string[] ports = SerialPort.GetPortNames();
        SerialPort[] serialport = new SerialPort[ports.Length];
        foreach(string p in ports)
        {
            int i = Array.IndexOf(ports, p);
            serialport[i].PortName = p;
            serialport[i].BaudRate = 9600;
            serialport[i].Open();
            //Scan inputs for "connectAlready"
        }

我不知道，并且我一直得到一个＆＃34; System.NullReferenceException＆＃34;在serialport [i] .PortName = p;

如何让这个程序运作？感谢您的所有帮助

Answer 1

此点

SerialPort[] serialport = new SerialPort[ports.Length];

您正在此处初始化阵列。但是在for循环的这一点上，

serialport[i].PortName = p;

该位置的SerialPort对象未初始化。因此，空引用异常

因此，在将任何内容分配给串行端口

之前，请尝试在for循环中添加它

serialport[i]=new SerialPort()

使用你需要的任何构造函数。

Answer 2

首先，您需要为您创建的每个串行端口声明新的串行端口对象：

    string[] ports = SerialPort.GetPortNames();
    SerialPort[] serialport = new SerialPort[ports.Length];
    foreach(string p in ports)
    {
        int i = Array.IndexOf(ports, p);
        serialport[i] = new SerialPort(); //note this line, otherwise you have no serial port declared, only array reference which can contains real SerialPort object
        serialport[i].PortName = p; 
        serialport[i].BaudRate = 9600;
        serialport[i].Open();
        //Scan inputs for "connectAlready"
    }

然后，您至少需要处理四件事情并处理您的数据：

串行端口DataReceived的事件处理程序

serialport[i].DataReceived += serialPort_DataReceived; //This is to add event handler delegate when data is received by the port

private void serialPort_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e) { //This is to handle the data when it comes
    //Do something on data received
}

从端口的基础流中获取数据。

private void serialPort_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e) {
    SerialPort serialPort1 = sender as SerialPort; 
    byte[] data = new byte[serialPort1.BytesToRead]; //this is to provide the data buffer
    Stream portStream = serialPort1.BaseStream;
    portStream.Read(data, 0, data.Length); //You get your data from serial port as byte[]
    //Do something on your data
}

Encoding.UTF8.GetString将输入数据从byte[]转换为ASCII个字符（编辑：考虑更改/跳过此步骤，如果收到的数据不是{{，请考虑步骤2 1}}但是byte[]）
```
ASCII
```
检查数据private void serialPort_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e) { SerialPort serialPort1 = sender as SerialPort; byte[] data = new byte[serialPort1.BytesToRead]; //this is to provide the data buffer Stream portStream = serialPort1.BaseStream; portStream.Read(data, 0, data.Length); //You get your data from serial port as byte[] string dataString = Encoding.UTF8.GetString(data); //here is your data in string //Do something on your data }是否包含您想要的数据
```
string
```

作为最后一点，请注意串口中的数据不会聚集在一起（例如＆＃34; conne＆＃34;然后＆＃34; ctAlready＆＃34;）。在这种情况下，您需要先在全局缓冲区中复制接收的数据，然后进行其他检查（使用bool hasData = dataString.Contains("connectAlready"); //this is to check if your data has this, if it doesn't do something）

Buffer.BlockCopy

C＃扫描COM端口以获取特定输入

2 个答案: