.NET线程和硬件访问的问题 [英] problem with two .NET threads and hardware access
问题描述
我正在创建一个应用程序，该应用程序通过FT2232H USB/RS232转换器与设备进行通信.为了进行通讯，我使用了FTDI网站上的FTD2XX_NET.dll库.
我正在使用两个线程:
当我尝试在接收方的线程运行时将任何数据写入设备时遇到问题.主线程只是挂在ftdiDevice.Write函数上.
我试图同步两个线程，以便只有一个线程可以同时使用读/写功能，但这没有帮助.
下面的代码负责通信.请注意，以下函数是FtdiPort类的方法.
I'm creating an application which communicates with the device via FT2232H USB/RS232 converter. For communication I'm using FTD2XX_NET.dll library from FTDI website.
I'm using two threads:
I've got a problem when I'm trying to write any data to the device while the receiver's thread is running. The main thread simply hangs up on ftdiDevice.Write function.
I tried to synchronize both threads so that only one thread can use Read/Write function at the same time, but it didn't help.
Below code responsible for the communication. Note that following functions are methods of FtdiPort class.
private void receiverLoop()
{
if (this.DataReceivedHandler == null)
{
throw new BackendException("dataReceived delegate is not set");
}
FTDI.FT_STATUS ftStatus = FTDI.FT_STATUS.FT_OK;
byte[] readBytes = new byte[this.ReadBufferSize];
while (true)
{
lock (FtdiPort.threadLocker)
{
UInt32 numBytesRead = 0;
ftStatus = ftdiDevice.Read(readBytes, this.ReadBufferSize, ref numBytesRead);
if (ftStatus == FTDI.FT_STATUS.FT_OK)
{
this.DataReceivedHandler(readBytes, numBytesRead);
}
else
{
Trace.WriteLine(String.Format("Couldn't read data from ftdi: status {0}", ftStatus));
Thread.Sleep(10);
}
}
Thread.Sleep(this.RXThreadDelay);
}
}
public void Write(byte[] data, int length)
{
if (this.IsOpened)
{
uint i = 0;
lock (FtdiPort.threadLocker)
{
this.ftdiDevice.Write(data, length, ref i);
}
Thread.Sleep(1);
if (i != (int)length)
{
throw new BackendException("Couldnt send all data");
}
}
else
{
throw new BackendException("Port is closed");
}
}
static Object threadLocker = new Object();
private void startReceiver()
{
if (this.DataReceivedHandler == null)
{
return;
}
if (this.IsOpened == false)
{
throw new BackendException("Trying to start listening for raw data while disconnected");
}
this.receiverThread = new Thread(this.receiverLoop);
//this.receiverThread.Name = "protocolListener";
this.receiverThread.IsBackground = true;
this.receiverThread.Start();
}
如果我在以下行中注释，则ftdiDevice.Write函数不会挂断:
The ftdiDevice.Write function doesn't hang up if I comment following line:
ftStatus = ftdiDevice.Read(readBytes, this.ReadBufferSize, ref numBytesRead);
推荐答案
几件事:
-
检查您的Read通话是否被阻止.如果是这样，您可能无法在Read阻止等待响应时调用Write.您的API文档可能对此有更多详细信息.
Check to see if your Read call is blocking. If so, you might not be able to call Write while the Read is blocking waiting for a response. Your API documentation may have more details on this.
某些API即使在同步访问时也无法很好地支持多个线程.如果是这种情况，您可以使用一种设计，在其中将Write命令委托给comm线程.过去使用此模式时，通常会排队某种包含我要编写的信息的Command类，并使用线程化Signal类来允许我的调用"command"方法来阻止或提供某种形式的信息.异步通知.
Some APIs do not support multiple threads very well, even when synchronizing access. If that's the case here, you can use a design where you delegate your Write commands to your comm thread. When I've used this pattern in the past, I typically queue up some sort of Command class containing the information I wish to write, and either use a threading Signal class to allow my calling 'command' methods to block or provide some sort of asynchronous notification.
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