在RXTX中收到的问题 [英] Issues receiving in RXTX

问题描述

我一直在使用RXTX大约一年，没有太多问题。我刚开始一个新的程序与一个新的硬件进行交互，所以我重用了我在其他项目中使用的connect（）方法，但我有一个我以前从未见过的奇怪问题。

I've been using RXTX for about a year now, without too many problems. I just started a new program to interact with a new piece of hardware, so I reused the connect() method I've used on my other projects, but I have a weird problem I've never seen before.

问题

设备工作正常，因为当我连接HyperTerminal时，我发送东西并收到我的期望，并且串行端口监视器（SPM）反映了这一点。

The device works fine, because when I connect with HyperTerminal, I send things and receive what I expect, and Serial Port Monitor(SPM) reflects this.

然而，当我运行简单的HyperTerminal-clone时，我编写了诊断我的主应用程序的问题，根据SPM发送字节，但没有收到，我的SerialPortEventListener永远不会触发。即使我在主循环中检查可用数据， reader.ready（）返回 false 。如果我忽略此检查，那么我会得到一个例外，详情如下。

However, when I run the simple HyperTerminal-clone I wrote to diagnose the problem I'm having with my main app, bytes are sent, according to SPM, but nothing is received, and my SerialPortEventListener never fires. Even when I check for available data in the main loop, reader.ready() returns false. If I ignore this check, then I get an exception, details below.

connect（）方法的相关部分

// Configure and open port
port = (SerialPort) CommPortIdentifier.getPortIdentifier(name)
                                      .open(owner,1000)
port.setSerialPortParams(baud, databits, stopbits, parity);
port.setFlowControlMode(fc_mode);
final BufferedReader br = new BufferedReader(
                            new InputStreamReader(
                              port.getInputStream(), 
                              "US-ASCII"));

// Add listener to print received characters to screen
port.addEventListener(new SerialPortEventListener(){
  public void serialEvent(SerialPortEvent ev) {
    try {
      System.out.println("Received: "+br.readLine());
    } catch (IOException e) { e.printStackTrace(); }
  }   
});
port.notifyOnDataAvailable();

例外

java.io.IOException: Underlying input stream returned zero bytes
        at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:268)
        at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:306)
        at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:158)
        at java.io.InputStreamReader.read(InputStreamReader.java:167)
        at java.io.BufferedReader.fill(BufferedReader.java:136)
        at java.io.BufferedReader.read(BufferedReader.java:157)
        at <my code>

重大问题（再次）

我认为我已经消除了所有可能的硬件问题，那么我的代码或RXTX库可能出现什么问题？

I think I've eliminated all possible hardware problems, so what could be wrong with my code, or the RXTX library?

编辑：有趣的东西

当我在发送一堆后打开HyperTerminal时来自java的应该得到响应的命令，所有的响应都会立即出现，好像它们已经放在某个缓冲区中，但是不可用。

When I open HyperTerminal after sending a bunch of commands from java that should have gotten responses, all of the responses appear immediately, as if they had been put in the buffer somewhere, but unavailable.

编辑2 ：尝试了一些新的，相同的结果

我运行了代码示例这里，结果相同。没有数据进入，但当我切换到新程序时，它立刻就出现了。

I ran the code example found here, with the same results. No data came in, but when I switched to a new program, it came all at once.

编辑3

硬件很好，即使是不同的计算机也有同样的问题。我没有使用任何类型的USB适配器。

The hardware is fine, and even a different computer has the same problem. I am not using any sort of USB adapter.

我已经开始使用 PortMon ，它给了我一些有趣的结果。 HyperTerminal和RXTX没有使用相同的设置，并且RXTX总是轮询端口，与HyperTerminal不同，但我仍然无法看到哪些设置会影响这一点。一旦我可以将配置与常量轮询隔离，我就会发布我的PortMon日志。

I've started using PortMon, too, and it's giving me some interesting results. HyperTerminal and RXTX are not using the same settings, and RXTX always polls the port, unlike HyperTerminal, but I still can't see what settings would affect this. As soon as I can isolate the configuration from the constant polling, I'll post my PortMon logs.

编辑4

过去3个月内某种类型的Windows更新是否可能导致此问题？它已经搞砸了我的一个基于MATLAB mex的程序。

Is it possible that some sort of Windows update in the last 3 months could have caused this? It has screwed up one of my MATLAB mex-based programs once.

编辑5

我还注意到HyperTerminal，RXTX和我发现与设备通信的单独程序之间有些不同的东西（但是没有做我想要的，这就是为什么我在编写我自己的程序）

I've also noticed some things that are different between HyperTerminal, RXTX, and a separate program I found that communicates with the device (but doesn't do what I want, which is why I'm rolling my own program)

• 超级终端 - 设置为无流量控制，但串口监视器的RTS和DTR指示灯为绿色


• 其他程序 - 不确定它认为它正在使用什么设置，但只有SPM的RTS指示器为绿色


• RXTX - 无论我设置什么流量控制，只有SPM的CTS和DTR指示灯亮。

来自Serial Port Monitor的帮助文件（转述）：

From Serial Port Monitor's help files (paraphrased):

the indicators display the state of the serial control lines

  RTS - Request To Send
  CTS - Clear To Send
  DTR - Data Terminal Ready

推荐答案

好的，对不起，我花了很长时间才回到这个问题。以下是我的工作方式。

OK, sorry it's taken me so long to come back to this question. Here's how I got things working.

注意：此方法 NOT 适用于所有人，请在复制/粘贴之前阅读以下内容你自己的代码

Note: This method will NOT work for everyone, please read below before copy/pasting into your own code

public void connect(CommPortIdentifier portId) throws Failure {
    if (portId == null)
        throw new Failure("No port set");

    try { port = (SerialPort) portId.open(getClass().getName(), 10000); } 
    catch (PortInUseException e) {
        throw new Failure("Port in use by " + e.currentOwner,e); }

    try {
        port.setSerialPortParams(9600, SerialPort.DATABITS_8,
                SerialPort.STOPBITS_1, SerialPort.PARITY_NONE);
        port.setFlowControlMode(SerialPort.FLOWCONTROL_RTSCTS_IN
                              | SerialPort.FLOWCONTROL_RTSCTS_OUT);
    } catch (UnsupportedCommOperationException e) { throw new Failure(e); }

    port.setRTS(true);

    // More setup
}

所以，在我的案例，问题是我的特定设备需要RTS流量控制。其他设备可能需要不同的东西（CTS，XON / XOFF），因此请检查该设备的手册。默认情况下，RXTX禁用所有流量控制机制（与Hypertrm或其他程序不同）。启用每个过程分为两个步骤。

So, in my case, the problem was that my particular device requires RTS flow control. Other devices may require different things (CTS, XON/XOFF), so check that device's manual. By default, RXTX disables all flow control mechanisms (unlike Hypertrm or other programs). Enabling each one is a two-step process.

1. 获得SerialPort对象后，调用 setFlowControlMode（） 方法，并按位OR（' | '）必要的 SerialPort.FLOWCONTROL _ 常量


2. 将适当的流量控制设置为true或false（就像我使用 port.setRTS（true））

1. Once you have a SerialPort object, call the setFlowControlMode() method, and bitwise-OR ('|') the necessary SerialPort.FLOWCONTROL_ constants
2. Set the appropriate flow control to true or false (like I did with port.setRTS(true))

对于有类似问题的其他人，如果这不起作用，我建议

For the others with similar problems, if this doesn't work, I suggest

1. 使用串口监控程序，如串口监控器和/或< a href =http://technet.microsoft.com/en-us/sysinternals/bb896644.aspx =noreferrer> PortMon （两个Windows），看看实际发生了什么。


2. 通过[e-mail]向RXTX开发人员发送电子邮件（非常有帮助）

1. Using a serial port monitoring program like Serial Port Monitor and/or PortMon (both Windows) to see what is actually going on.
2. Emailing the RXTX developers at [e-mail] (they are very helpful)

这篇关于在RXTX中收到的问题的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！