Question

我正在收听5字节信息的串口。轮询的完整答案需要5个字节。我的代码侦听serialport data_received事件并检查bytesToRead。有时，事件将触发并且bytesToRead为0.仅当数据可用时才触发事件吗？

public SerialPort wheel = new SerialPort();
public void wheel_DataReceived(object sender, EventArgs e)
{
    if (wheel.BytesToRead < 5)
    {
        wheelRetry += 1;
        Log("Wheel Data Received: " + wheel.BytesToRead.ToString() + 
            " bytes. Need 5 bytes. Attempt #: " + wheelRetry.ToString());
    }

Answer 1

您可以设置ReceivedBytesThreshold属性：

var port = new SerialPort();
port.Open();    

//Only raise the event if 5 bytes have been received
port.ReceivedBytesThreshold = 5;

port.DataReceived += (s, e) =>
{
    //Handle the data
};

请注意，您应该在打开端口后挂钩事件处理程序，
这是为了防止某些平台上的已知问题阻止事件发生如果它在港口被打开之前被连接起来了。

Answer 2

根据reference source for SerialPort.cs，是的，DataReceived事件可以在BytesToRead为0时触发，如果内部流＆＃39; s DataRecieved事件被触发，事件args有EventType == SerialData.Eof。如果是这种情况，那么BytesToRead的大小就不会被考虑在内。

来自CatchReceivedEvents的相关摘录，内部流的DataReceived事件处理程序：

bool raiseEvent = false;
try {
    raiseEvent = stream.IsOpen && (SerialData.Eof == e.EventType || BytesToRead >= receivedBytesThreshold);    
}
catch {
    // Ignore and continue. SerialPort might have been closed already! 
}
finally {
    if (raiseEvent)
        eventHandler(this, e);  // here, do your reading, etc. 
}

您可以修改您的事件处理程序，如@elgonzo建议的那样，以便您可以查看EventType：

public void wheel_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
    if(e.EventType == SerialData.Eof) //return? possibly nothing to read
...

C＃SerialPort DataReceived事件

2 个答案: