I'm writing a program that listens on a Serial Port. I already have code that utilizes the VCP drivers (Virtual COM Port) to open a serial connection and then add an event handler for any time data is received. That code roughly looks like this:
public void OpenPort(string portNumber)
{
_port = new SerialPort(
portName: portNumber,
baudRate: 9600,
parity: Parity.None,
dataBits: 8,
stopBits: StopBits.One
);
_port.DataReceived += ReadData;
}
private void ReadData(object sender, SerialDataReceivedEventArgs e)
{
string data = _port.ReadExisting().Trim();
Console.WriteLine("Received: " + data);
}
This works great. It's very easy for me to understand how to set up events using the += notation. But I'm trying to switch over from using the VCP drivers to instead using the D2XX drivers provided by FTDI. I have most of the equivalent code that I need written, with the notable exception of being able to read data whenever a "data received" event occurs.
The D2XX driver includes one method for setting up event handlers whenever data is received, called SetEventNotification. Here's what the method signature looks like:
SetEventNotification(UInt32 eventMask, EventWaitHandle eventHandle);
The first parameter is straight-forward enough (they have some predefined uints you can pass in to determine when the event should trigger), but I've never worked directly with EventWaitHandles before, and I found the documentation difficult to grasp, so I'm having trouble getting started.
At the end of the day... I would like to have an event listener method which performs a read task, and which I can assign using the += operator, as I did above with the VCP driver.
Based on what I was reading, it looks like I'll have to create a new Thread that essentially polls continuously for the EventWaitHandle's signal? Or something like that? Any examples or sample code to get me started (or finished!) would be appreciated.
Here's what I have so far:
public void OpenPort(string portNumber)
{
_port = new FTDI();
var status = _port.OpenBySerialNumber(portNumber);
if (FTDI.FT_STATUS.FT_OK != status) throw new Exception();
status = _port.SetBaudRate((UInt32) 9600);
if (FTDI.FT_STATUS.FT_OK != status) throw new Exception();
status = _port.SetDataCharacteristics(
DataBits: FTDI.FT_DATA_BITS.FT_BITS_8,
StopBits: FTDI.FT_STOP_BITS.FT_STOP_BITS_1,
Parity: FTDI.FT_PARITY.FT_PARITY_NONE
);
if (FTDI.FT_STATUS.FT_OK != status) throw new Exception();
var evHandle = new EventWaitHandle(false, EventResetMode.AutoReset, "");
_port.SetEventNotification(FTDI.FT_EVENTS.FT_EVENT_RXCHAR, evHandle);
// ... now what?
}
public void ReadData(object sender, EventArgs e)
{
UInt32 bytesAvailable = 0;
_port.GetRxBytesAvailable(ref bytesAvailable);
string data;
UInt32 bytesRead = 0;
_port.Read(out data, bytesAvailable, ref bytesRead);
data = data.Trim();
Console.WriteLine("Received: " + data);
}
I'll have to create a new Thread that essentially polls continuously for the EventWaitHandle's signal
Polls, no. But waits, yes. All that an event handle can do is let a thread sleep until the event is signaled. Note that "event" here means something completely different from a C# "event", though of course you can use the former as part of an implementation of the latter.
Frankly, it's not clear at all why you are headed down this part. Are you dealing with data transmitted over the standard serial port? If so, then there should never be any need to use some third-party API; Windows and .NET provide all you need, and you should stick with that. What does using this third-party API gain you that you are unable to accomplish using the standard SerialPort class?
As far as the event itself goes, without more context (and no, it's unlikely anyone would sift through the PDF you linked to figure out how to produce a turn-key solution for you), all one can offer is a general outline of how you can use the event handle to implement an event:
public event EventHandler DataReceived;
private bool _done;
private void PortListener(EventWaitHandle waitHandle)
{
while (true)
{
waitHandle.WaitOne();
if (_done)
{
break;
}
EventHandler handler = DataReceived;
if (handler != null)
{
handler(this, EventArgs.Empty);
}
}
}
public void StartListening(EventWaitHandle waitHandle)
{
_done = false;
new Thread(() => PortListener(waitHandle)).Start()
}
public void StopListening(EventWaitHandle waitHandle)
{
_done = true;
waitHandle.Set();
}
The above provides a DataReceived C# event that is raised any time the wait handle is signaled. It assumes an auto-reset event. You can also use manual reset, simply by (of course) manually resetting the event handle any time it's signaled and you've raised the C# event.
To do this, it simply maintains an internal flag _done indicating whether the thread should be running or not, and provides the Start... and Stop... methods, which clear the flag and start the thread with its loop, and set the flag and signal the event, respectively.
Related
After a long time i need to program again.
I need to constantly send a command through serial port from a car ecu(? data).
Then i need to receive that data which i will process to be shown on a display(thinking racing display with car parameters like temperature etc).
I need to do this constantly
I wonder before i start whats best way to do this?
1 thread for constantly asking and receiving data
main thread for showing data in screen.
(store data in buffer and save once a minute or so)
anyone has any tips a guide or so how to start on this.
i tested receiving data with terminal and i got data back so config is working.
sent ? data => i got data back.
You could just use the SerialPort class and configure the BaudRate, DataBits etc.. and then just wait for the DataReceived event to fire:
public class SerialPortReader
{
public SerialPortReader(string yourPortName)
{
var serialPort = new SerialPort() {
PortName = yourPortName,
BaudRate = 57600; //This will control the rate at what you receive the data
}
serialPort.DataReceived += new SerialDataReceivedEventHandler(OnDataReceived);
serialPort.Open();
}
}
public void OnDataReceived(object sender, SerialDataReceivedEventArgs e)
{
var serialPort = (SerialPort)sender;
// Process your data reading the stream with Read, ReadLine etc...
}
The approach we are using in our SerialPort Handler is, to have an AutoResetEvent to get notified as soon as there is an answer from the port.
SerialPort class of the FrameWork has a few issues with the integrated DataReceived event. It is sometimes fired when there is no complete package available (in case you defined the answer length). So you should check for the answer length you expect.
Our very stripped down implementation:
public class Serialport
{
private SerialPort _serialPort;
private List<byte> _buffer;
private AutoResetEvent _autoResetEvent;
private const int WriteTimeOut = 5;
private event EventHandler ReceivedDataChanged;
public Serialport()
{
_serialPort = new SerialPort();
// set PortName, BaudRate etc
_serialPort.Open();
_serialPort.DiscardInBuffer();
_serialPort.DiscardOutBuffer();
_serialPort.DataReceived += ReceiveData;
}
private void ReceiveData(object sender, SerialDataReceivedEventArgs e)
{
var bytes = _serialPort.BytesToRead;
byte[] buffer = new byte[bytes];
if (_serialPort.IsOpen)
{
_serialPort.BaseStream.Read(buffer, 0, bytes);
_buffer.AddRange(buffer);
}
ReceivedDataChanged?.Invoke(this, new ReceivedBytesEventArgs(_buffer.ToArray()));
_buffer.Clear();
}
private void SendData(byte[] message, int answerLength)
{
_serialPort.ReceivedBytesThreshold = answerLength;
_serialPort.WriteTimeout = WriteTimeOut;
_serialPort.Write(message, 0, message.Length);
}
public string SendDataCommand()
{
if (_serialPort.IsOpen)
{
ReceivedDataChanged += InterpretAnswer;
SendData(message, length);
if (_autoResetEvent.WaitOne(100))
{
ReceivedDataChanged -= InterpretAnswer;
//Data Received and interpreted and send to the caller
return _requestAnswer;
}
ReceivedDataChanged -= InterpretAnswer;
}
return "Connection not open";
}
private void InterpretAnswer(object sender, EventArgs e)
{
// handle all interpretation
// Set the event
_autoResetEvent.Set();
}
}
The serialPort is initialised and opened. After that, we wire up all needed events and call the SendDataCommand() Method. This method is the public visible method which is called from some task. This calls the method SendData. As soon as there is an answer, the event is triggered and the interpretation is started. If the interpretation is done in the specified amount of time (_autoResetEvent.WaitOne(msToWait)) the result is given back to the calling method.
This should be done in a separate task, so the ui will not Block while you wait for the answer
As mentioned, this is a very stripped down example. You should do more checking in the received handler of SerialPort, because there are some issues with the event. With this approach you will have a bit more of abstraction to your business logic.
Hope this helps.
I'm quite new to C# and certainly OOP concepts.. so forgive the stupidity of my question.
I have a system I wish to communicate with, It has a number of commands that can be called with an associated response. (Communication is done via TCP/IP or Serial) (I implemented an Interface with SendMessage so that I can use multiple transport mechanisms)
I want to create a method for each command and then expose these, which is simple enough. The device also lets say 'broadcasts' messages as well which I want to act on, so I was using an event handler for this which works well..
At the moment in the event handler I catch OK and ERROR style messages, but ideally I would like to also be able to send the command from the above method and catch an error and return a bool value based on the command.
Can anyone think of a way I can do something like this and point me in the right direction?
Thanks
David
You can use helper to wait for event. Some ugly code from past:
public class ComWait
{
ManualResetEvent _waitEvent;
SomeEvent _eventHandler;
public ComWait()
{
_waitEvent = new ManualResetEvent(false);
_eventHandler = new SomeEvent(Watch);
}
void Watch()
{
_waitEvent.Set();
}
public bool Wait(int time = 3000)
{
_waitEvent.Reset();
SomeEvent += _eventHandler;
bool result = _waitEvent.WaitOne(time, false);
SomeEvent -= _eventHandler;
return result;
}
}
Usage is
ComWait wait = new ComWait();
if(!wait.Wait())
return; // timeout
// process
It will simply block synchronous method until event is rised or timeout occurs. It should be easy to add parameters: to unblock on specific event and to pass event handler parameters back to caller.
Otherwise I would simply have method inside communication class to use as a blocker:
readonly object _waitLock = new object();
public void Wait()
{
lock (_waitLock)
if (!Monitor.Wait(_waitLock, 3000))
throw new TimeoutException("No communications");
}
Signal at same time as you rise event:
lock (_waitLock)
Monitor.PulseAll(_waitLock);
I have a USB device from which I need to read data via LibUsbDotNet.
If I use the following code after I've successfully opened the device...
protected UsbEndpointReader _libUsbReader = null;
protected UsbEndpointWriter _libUsbWriter = null;
.
IUsbDevice wholeUsbDevice = PhysicalLibUSBDevice as IUsbDevice;
if (!ReferenceEquals(wholeUsbDevice, null))
{
// This is a "whole" USB device. Before it can be used,
// the desired configuration and interface must be selected.
// Select config #1
wholeUsbDevice.SetConfiguration(1);
// Claim interface #0.
wholeUsbDevice.ClaimInterface(0);
}
// Create the reader and writer streams
_libUsbReader = PhysicalLibUSBDevice.OpenEndpointReader(LibUsbDotNet.Main.ReadEndpointID.Ep01);
_libUsbWriter = PhysicalLibUSBDevice.OpenEndpointWriter(LibUsbDotNet.Main.WriteEndpointID.Ep02);
_libUsbReader.DataReceivedEnabled = true;
_libUsbReader.DataReceived += OnDataReceived;
_libUsbReader.ReadThreadPriority = System.Threading.ThreadPriority.Highest;
_libUsbReader.ReadBufferSize = 32;
and define the method:
private void OnDataReceived(object sender, EndpointDataEventArgs e)
{
Console.WriteLine("Data received");
}
The event never fires. I know the packets are being received by my code as I have a USB analyser attached and can see them coming in.
If I change the code to remove the reliance upon the event callback and instead use the loop below on a background thread to read the reader object
while(true)
{
ErrorCode ec = ErrorCode.None;
Thread.Sleep(5);
int bytesRead;
byte[] buffer = new byte[32];
ec = _libUsbReader.Read(buffer, 1000, out bytesRead);
if(bytesRead>0) Console.WriteLine("Data Received");
}
Then everything works great.
I've tried playing around with the order I initialise, the values etc and can still get no joy. Can anyone suggest why the events aren't firing if I use the DataReceived event?
I'm using LibUsbDotNet 2.2.8.
I know this is old, but in your code:
...
_libUsbReader.DataReceivedEnabled = true;
_libUsbReader.DataReceived += OnDataReceived;
_libUsbReader.ReadThreadPriority = System.Threading.ThreadPriority.Highest;
_libUsbReader.ReadBufferSize = 32;
...
I have DataReceivedEnabled set after DataReceived (not sure if this makes a difference).
Also, I do not change thread priority and ReadBufferSize. The latter is 4096 by default. When data arrives, the EndpointDataEventArgs parameter to the event has the Count property with the actual number of bytes received.
Hope this helps.
Please try like this:
_libUsbReader.DataReceived += mEp_DataReceived;
private void mEp_DataReceived(object sender, EndpointDataEventArgs e)
{
try
{
Invoke(new OnDataReceivedDelegate(OnDataReceived), new object[] { sender, e });
}
catch
{
closeDevice();
}
}
When opening the endpoint for reading, you should define the endpoint type to interrupt, otherwise the Datarecieve event won't fire.
(Optionally define the size of the read buffer)
In your code you'll have to modify just this row:
_libUsbReader = PhysicalLibUSBDevice.OpenEndpointReader(LibUsbDotNet.Main.ReadEndpointID.Ep01, 64, EndpointType.Interrupt);
I think the sollution is that you should read the endpoint content at the event (or discard it). I had the same problem, when only printing at the console the message I only entered 1 time. When I process in the event the data on the endpoint with read command, the problem seems to be solved.
After much research I am still stumped. I have a serial port object which is reading data continuously. What I am able to do it generate the dataReceived event, communicate with the port, and output the received values to the debug window. So, I'm pretty sure it's all working physically. The problem is when I try to pass the serial port output to my original thread I get an error. It says I can't have thread cross talk (or something to that effect). I've been trying to use a backgroundWorker but I'm not sure that is the solution I want plus with my novice skills it's a little over my head. And I tried to use invoke but the method doesn't seem to be available. (I might be calling from the wrong object?) Anyway section is below.
namespace Photometer
{
class csRadiometerILT1700
{
//manufacturer specs for baud rate, databits, and stop bits
static string portName="COM1";
static int baudRate = 1200;
static int dataBits = 8;
//instantialize a serial port object for the Radiometer
private SerialPort RadiometerSerial = new SerialPort(portName, baudRate, Parity.None, dataBits, StopBits.One);
//constructor
//public csRadiometerILT1700(Form ParentForm, Chart outputChart)
public csRadiometerILT1700()
{
//two handshaking properties of the ILT1700. Handshaking is enabled and
//http://stackoverflow.com/questions/6277619/problem-reading-serial-port-c-net-2-0-to-get-weighing-machine-output
RadiometerSerial.Handshake= Handshake.RequestToSend;
RadiometerSerial.DtrEnable = true;
RadiometerSerial.DataReceived += new SerialDataReceivedEventHandler(RadiometerSerial_DataReceived);
}
public void openPort()
{
if (!RadiometerSerial.IsOpen)
{
RadiometerSerial.Open();
}
}
public void closePort()
{
RadiometerSerial.Close();
}
string RadiometerVoltageReadingString;
int RadiometerVoltageReadingInt;
private void RadiometerSerial_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
//It's here that this.invoke()... cannot be called.
RadiometerVoltageReadingString= (RadiometerSerial.ReadExisting().ToString()); //y-value
Debug.Print(RadiometerVoltageReadingString.ToString());
makeRadioReadingDouble(RadiometerVoltageReadingString);
}
private void makeRadioReadingDouble(string inputVoltageString)
{
List<double> outputVoltageDouble=new List<double>(2);
if (!(inputVoltageString == "\r\n" || inputVoltageString == ""))
{
string[] voltageValAndExpo = inputVoltageString.Split(new string[] { "e", "\r\n" }, StringSplitOptions.RemoveEmptyEntries);
for (int inCounter = 0; inCounter < voltageValAndExpo.Count(); inCounter=inCounter+2)
{
double voltageVal = Convert.ToDouble(voltageValAndExpo[inCounter]);
double voltageExpo = Convert.ToDouble(voltageValAndExpo[inCounter + 1]);
outputVoltageDouble.Add(Math.Pow(voltageVal, voltageExpo));
}
}
}
}
}
This is all called when I form loads with the code
csRadiometerILT1700 Radiometer;
...
Radiometer = new csRadiometerILT1700();
Radiometer.openPort();
Any insight is appreciated.
EDIT:
I altered my csRadiometerILT1700 constructor to
public csRadiometerILT1700(Form inputForm)
{
//inputForm.Invoke(
//two handshaking properties of the ILT1700. Handshaking is enabled and
//http://stackoverflow.com/questions/6277619/problem-reading-serial-port-c-net-2-0-to-get-weighing-machine-output
RadiometerSerial.Handshake= Handshake.RequestToSend;
RadiometerSerial.DtrEnable = true;
RadiometerSerial.DataReceived += new SerialDataReceivedEventHandler(RadiometerSerial_DataReceived);
inputForm.Invoke(DataReceived);
}
and declare
public event Delegate DataReceived;
in the csRadiometerILT1700 class. But this gives me the error of "Datareceived must be of a delegate type." How do I resolve this now? Am I on the right track?
Your RadiometerILT1700 class needs an event to report it's received (and processed) data.
Your Form subscribes to that event
The Forms eventhandler uses this.Invoke() to overcome the cross-threading issue.
Invoke is a method on a Delegate or a Form or Control, since csRadiometerILT1700 is none of these it is not inheriting an Invoke implemenation from those classes.
You will need to raise another event to the caller of csRadiometerILT1700 and hadle that on you GUI somewhere (along with any cross thread issues.) Alternatively, you could provide csRadiometerILT1700 with a delegate it could use to callback, kind of like a hand rolled event.
Once you have the data in your Form you can use Control.InokeRequired to detect a cross thread situation and Control.Invoke to make the cross thread call.
anytime you try to post to the main thread from a different thread you'll get this error. You need to use a delegate and Invoke on the control you want to call from the thread that isn't the main form thread.
Assuming the error is actually:
Control control name accessed from a thread other than the thread it
was created on.
The problem is you can't affect your GUI from another thread. You need to invoke the form or control to pass control so it can be modified. You should be able to interact with most other elements, but not a form.
You should not call this.Invoke there, the way you are doing it is like trying to sync your own thread with your own instead with the UI. you should call formhandle.Invoke, or inside form class register for the event and then you can use this.invoke
I have wrote a simple client that use TcpClient in dotnet to communicate. In order to wait for data messages from server i use a Read() thread that use blocking Read() call on socket. When i receive something i have to generate various events. These event occur in the worker thread and thus you cannot update a UI from it directly. Invoke() can be use but for end developer its difficult as my SDK would be use by users who may not use UI at all or use Presentation Framework. Presentation framework have different way of handling this. Invoke() on our test app as Microstation Addin take a lot of time at the moment. Microstation is single threaded application and call invoke on its thread is not good as it is always busy doing drawing and other stuff message take too long to process.
I want my events to generate in same thread as UI so user donot have to go through the Dispatcher or Invoke.
Now i want to know how can i be notified by socket when data arrive? Is there a build in callback for that. I like winsock style receive event without use of separate read thread. I also do not want to use window timer to for polling for data.
I found IOControlCode.AsyncIO flag in IOControl() function which help says
Enable notification for when data is
waiting to be received. This value is
equal to the Winsock 2 FIOASYNC
constant.
I could not found any example on how to use it to get notification. If i am right in MFC/Winsock we have to create a window of size(0,0) which was just used for listening for the data receive event or other socket events. But i don't know how to do that in dotnet application.
Ok I got it up and running. What I was really looking to was how to seamlessly post events to an UI thread, in which my connection is created. After going through framework code I came up with following proof of concept. SynchronizationContext can be use to bind my component to the UI thread that created it. Then I can post events to that UI thread directly, without using Invoke.
In the following example I created a ThreadUISafeTimer which uses a seperate thread, just like my socket client that uses one for reading and raising events. In this case, context is used to post the event if not null, otherwise the event is raised using the worker thread.
[DefaultEvent("Tick")]
public class ThreadUISafeTimer : Component
{
private const int True = 1;
private const int False = 0;
private int enabled = False;
private SynchronizationContext context;
public event EventHandler Tick = delegate { };
[DefaultValue(false)]
public ushort Interval { get; set; }
public ThreadUISafeTimer() {
Interval = 100;
this.Events.AddHandler("Tick", Tick);
//If this class is created by a UI thread it will always post the Tick event to it.
//otherwise it would be null and Tick would occur in a seperate thread.
context = SynchronizationContext.Current;
}
protected override bool CanRaiseEvents {
get {
return true;
}
}
[DefaultValue(false)]
public bool Enabled {
get {
return enabled == True;
}
set {
int newval = value ? True : False;
if (enabled != newval) {
if (newval == False)
Thread.VolatileWrite(ref enabled, False);
else {
enabled = True;
ThreadPool.QueueUserWorkItem(
new WaitCallback(delegate(object o) {
try {
do {
try {
Thread.Sleep(Interval);
if (Thread.VolatileRead(ref enabled) == True) {
var callback = new SendOrPostCallback(delegate(object arg) {
try {
Tick(this, EventArgs.Empty);
}
catch (Exception exp) {
Application.OnThreadException(exp);
return;
}
});
//If context is null raise Tick event from current thread
if (context == null)
callback(null);
else
//otherwise post it to the UI thread that owns this timer.
context.Post(callback, null);
}
}
catch (ThreadInterruptedException) {
}
} while (Thread.VolatileRead(ref enabled) == True);
}
catch (ThreadAbortException) {
}
}), null);
}
}
}
}
Take a look at this question which is roughly the same and solved by using the Event Broker pattern.
Sending instructions to a thread which is waiting for TCP?
Basically you would have one object with an event that all your threads subscribe to. It will also have a method that can be called which will invoke the event. It maybe sounds complicated, but its fairly simple.
Example code is here http://msforge.net/blogs/paki/archive/2007/11/20/EventBroker-implementation-in-C_2300_-full-source-code.aspx.