I'm taking data from a serial instrument for plotting on a chart. The data stream is 230 kbps, and the serial pipeline is less than 50% full, data arrives about 100 kbps and actually doesn't vary really and rate or quantity.
Having used just a serial terminal program, like Teraterm, on the same computer; I can capture data and prove that both the source of the data as well as the test reception method are fine and I see no errors to the captured data.
The Windows Forms application I'm developing loses data. I've reduced it from receiving, capturing (in parallel), parsing, and plotting, to just receiving and capturing. And have found that I still see lost data in the capture.
I'm not a long experienced Windows person, so therefore may not know of better ways to accomplish the same functions. Here are the actions I'm taking to perform receive actions:
I'm using a System.IO.Ports.SerialPort class.
I modify the .DataReceived event via:
+= new SerialDataReceivedEventHandler(comPort_DataReceive);
I then call the open() method.
Note: I may be doing something incorrect here, I never clear the .DataReceived event with a -= at any point, instead each time I open, the event is added yet again. Nevertheless, these problems occur even when I've only talked to the port once.
Here's my code for the data receive function. RxString is a string.
private void comPort_DataReceive(object sender, SerialDataReceivedEventArgs e)
{
RxString = comPort.ReadExisting();
this.Invoke(new EventHandler(ParseData));
}
private void ParseData(object sender, EventArgs e)
{
// Save to capture file, if capture is enabled
if ((WriteToFileEnabled == true) && (WriteToFileName != null))
{
writeFileHandle.Write(RxString);
}
return;
// Previously would parse and plot data
}
So, how would persons execute a receive in this situation to get this data without losing it?
Follow on questions are things like: How big is the buffer for serial receive, or do I need to worry about that if I have a reasonably responsive application? Flow control is irrelevant, the remote device is going to send data no matter what, so it would be up to my computer to take that data and process it or ignore it. But how would I know if I've lost data or experienced framing errors and stuff? (I ask that last one without having searched much on the SerialPort class structure, sorry.)
Lets assume that your device is sending messages that are 85 bytes in length. The DataReceive event handler may or may not fire once to receive those 85 bytes. Since it might fire more than once your code must account for that. The DataReceive event handler should read the bytes available and append them to a buffer that is processed later.
Also, only one of the events raised by the SerialPort class can execute at a time. In the example assume the handler has to fire three times to receive the 85 bytes. While processing the first part the other two can't execute. If while processing the first part one of the other events, PinChanged or ErrorReceived, are needed they can't be executed either.
My first two experiences with the SerialPort class were a 9600 bps terminal and a 1 Mbps bluetooth device. What worked for the slower did not work for the faster, but when I figured out how to get the faster to work the slower could use the same methodology.
My methodology:
Before opening the serial port I start two other background threads that run in a do loop. The first one(Receive) reads all available bytes from the serial port, adds them to a buffer, and signals the second thread on every read. The second one(Protocol) determines if a full message has arrived, does any byte to string conversion, updates the UI, etc. Depending on the application I may start a third thread that handles errors and pin changes. All of these threads are throttled by a Threading AutoResetEvent.
My DataReceive event handler has one line in it, a Set on the AutoResetEvent that is throttling Receive.
A VB example of this can be found here SerialPort Methodology. Since adopting this methodology I have not had any of the problems that seem to plague other SerialPort users and have used it successfully with speeds up to 2Mbps.
I developed a C# application for reading calls from GSM Modem. I used a timer to read the port regularly and notify me when there is a incoming call.
Now i am trying to use another timer which will write AT+CSQ -To know the signal quality, on the port and read the port for the quality value. In both the timers i used regular expressions to match and separate the data i need. Now the problem is that only my timer2 which is reading the signal quality is only working but not timer reading for incoming calls.
Timer reading signal strength:
private void tmr_sig_quality_Tick(object sender, EventArgs e)
{
if (port.IsOpen)
{
port.WriteLine("AT+CSQ");
string s= port.ReadExisting();
var match= Regex.Match(s,#"\+CSQ: (\d+),(\d+)");
if (match.Success)
{
progressBar1.Value = int.Parse(match.Groups[1].Value);
}
}
}
Timer reading incoming calls:
private void timer1_Tick(object sender, EventArgs e)
{
s = port.ReadExisting();
var match = Regex.Match(s, "RING[^\\+]*\\+CLIP:\\s*\"(?<phone>[^\"]*)\",(\\d+),\"([^\"]*)\",(\\w*),\"(\\w*)\",(\\w*)");
if (match.Success && s.Contains("RING"))
{
incall_status.Text = "Incoming Call...." + match.Groups["phone"].Value;
incall_status.Visible = true;
}
}
Why is this happening and solution please?
Two major problems. First is ReadExisting(), that will always return an empty string. Except when you are debugging and stepping through the code line by line. That gives the modem enough time to send the response. But this won't work when you run at full speed, you'll need to make a blocking call that ensures your program waits long enough to get all the returned characters. Use ReadLine() instead.
Second killer problem is that you are mixing commands. Your tmr_sig_quality_Tick() method is likely to read whatever timer1_Tick() was supposed to read. You'll need to re-think this approach. Something like a queue of commands that doesn't advance until the response to a command is received.
Not an actual answer to your question, but a general advice for communicating with a GSM modem:
Keep in mind that you have only one serial port, thus only one communication channel. A GSM modem can send spontaneous events, such as the RING, FAX, VOICE events, so there is no guarantee that when you write AT+CSQ the first reply is what you expect, i.e. the signal quality.
Having two timers like you're intending is not a good idea since you'll eventually end up with the response of one command in timer A when it was expected in B, because A read one of the spontaneous events...etc.
A much better and robust way is to have a worker thread that reads and interprets the incoming data and then distributes that in you application as needed. It can also handle the outgoing data. Use concurrent queues and some signaling mechanism (i.e. AutoResetEvent) for exchanging data with this thread, that way you get a cleaner interface to your hardware device and don't need to worry about timing and such in your application.
To start I am coding in C#. I am writing data of varying sizes to a device through a socket. After writing the data I want to read from the socket because the device will write back an error code/completion message once it has finished processing all of the data. Currently I have something like this:
byte[] resultErrorCode = new byte[1];
resultErrorCode[0] = 255;
while (resultErrorCode[0] == 255)
{
try
{
ReadFromSocket(ref resultErrorCode);
}
catch (Exception)
{
}
}
Console.WriteLine(ErrorList[resultErrorCode[0] - 48]);
I use ReadFromSocket in other places, so I know that it is working correctly. What ends up happening is that the port I am connecting from (on my machine) changes to random ports. I think that this causes the firmware on the other side to have a bad connection. So when I write data on the other side, it tries to write data to the original port that I connected through, but after trying to read several times, the connection port changes on my side.
How can I read from the socket continuously until I receive a completion command? If I know that something is wrong with the loop because for my smallest test file it takes 1 min and 13 seconds pretty consistently. I have tested the code by removing the loop and putting the code to sleep for 1 min and 15 seconds. When it resumes, it successfully reads the completion command that I am expecting. Does anyone have any advice?
What you should have is a separate thread which will act like a driver of your external hardware. This thread will receive all data, parse it and transmit the appropriate messages to the rest of your application. This portion of code will give you an idea of how receive and parse data from your hardware.
public void ContinuousReceive(){
byte[] buffer = new byte[1024];
bool terminationCodeReceived = false;
while(!terminationCodeReceived){
try{
if(server.Receive(buffer)>0){
// We got something
// Parse the received data and check if the termination code
// is received or not
}
}catch (SocketException e){
Console.WriteLine("Oops! Something bad happened:" + e.Message);
}
}
}
Notes:
If you want to open a specific port on your machine (some external hardware are configured to talk to a predefined port) then you should specify that when you create your socket
Never close your socket until you want to stop your application or the external hardware API requires that. Keeping your socket open will resolve the random port change
using Thread.Sleep when dealing with external hardware is not a good idea. When possible, you should either use events (in case of RS232 connections) or blocking calls on separate threads as it is the case in the code above.
I working on an application handling serial port communication. It's a WPF, multithreaded application. Everything went fine until I sent only small packages through the COM port with communication.
No I reached a phase, where I have to listen for data sent to my application on COM port. For this big chunk of data I go into trouble. I have only one DataReceived event fired, which reads part of the data I need. But after that there is no DataReceived event fired anymore for the rest of the data.
If I monitor the COM port I saw that the bytes are there, the monitoring software states, that there are 2067 bytes in the in queue, but the event do not fire.
I searched Google for similar problems, but I was unable to find relevant answers for this. Have you got any idea where to start searching the roots of the problem.
Thanks in advance.
Here is the code of the DataReceived handler:
private void comPort_DataReceived( object sender, SerialDataReceivedEventArgs e )
{
do
{
new Thread(() =>
{
OnReceivingData(new ComPortCommunicationEventArgs(DataTransferDirections.Receiving, DataTransferActions.Start));
}).Start();
byte[] packetData = null;
try
{
IsReceiving = true;
int bytesToReadCount = comPort.BytesToRead;
if ( bytesToReadCount == 0 )
{
return;
}
packetData = new byte[bytesToReadCount];
comPort.Read(packetData, 0, bytesToReadCount);
}
finally
{
IsReceiving = false;
new Thread(() =>
{
OnReceivingData(new ComPortCommunicationEventArgs(DataTransferDirections.Receiving, DataTransferActions.End));
}).Start();
}
OnPacketReceived(new PacketReceivedEventArgs(comPort.PortName, packetData.ToList()));
} while ( comPort.BytesToRead > 0 );
}
What I found out meanwhile, that if I comment out the OnPacketReceived call - which just fires event for the UI with the received data - than the data processing works fine. So it's not a COM port communication error I think...
Update:
I found the solution for my problem. It was not related to serial port handling.
In one of my data processing threads I run into a loop, which was supposed to be finished on succesfull processing, but with not enough data it was just run continously. Doing that it was blocked the DataReceived event handler - which is still not fully clear for my why, since the two process should be on diffrerent threads I supposed. But it seems that I'm wrong with this.
Anyway I corrected the processing method, and no I receive the data from the serisl port.
Sorry to take your time, and thanks for your help anyway your ideas helped my localize this problem.
Br,
Csaba
I worked with COM ports 5 years ago, and I know how tricky it can get sometimes. All sorts of tricky problems happened with the Siemens device I used to work with :)
First off, I couldn't follow your code thoroughly, so I can't know for sure if your DataReceived routine is sane. I suggest you try to replace all that code inside comPort_DataReceived to something very simple, only for test purposes.
private static void comPort_DataReceived(
object sender,
SerialDataReceivedEventArgs e)
{
SerialPort sp = (SerialPort)sender;
string indata = sp.ReadExisting();
Console.WriteLine("Data Received:");
Console.Write(indata);
}
If it still doesn't work, then the problem is not in your code. If you don't know what else to try, I would mess with parameters such as SerialPort.DtrEnable and SerialPort.RtsEnable and see if something happens, because these also caused some not-in-the-manual bugs for me in the past.
Piece of code extracted from MSDN.
I've been fighting with this issue for a day and I can't find answer for it.
I am trying to read data from GPS device trough COM port in Compact Framework C#. I am using SerialPort class (actually my own ComPort class boxing SerialPort, but it adds only two fields I need, nothing special).
Anyway, I am running while loop in a separate thread which reads line from the port, analyze NMEA data, print them, catch all exceptions and then I Sleep(200) the thread, because I need CPU for other threads... Without Sleep it works fine, but uses 100% CPU.. When I don't use Sleep after few minutes the output from COM port looks like this:
GPGSA,A,3,09,12,22,17,15,27,,,,,,,2.6,1.6,2.1*3F
GSA,A,3,09,12,22,17,15,27,,,,,,,2.6,1.6,2.1*3F
A,A,3,09,12,22,17,15,27,,,,,,,2.6,1.6,2.1*3F
,18,12,271,24,24,05,020,24,14,04,326,25,11,03,023,*76
A,3,09,12,22,17,15,27,,,,,,,2.6,1.6,2.1*3F
3,09,12,22,17,15,27,,,,,,,2.6,1.6,2.1*3F
09,12,22,17,15,27,,,,,,,2.6,1.6,2.1*3F
,12,22,17,15,27,,,,,,,2.6,1.6,2.1*3F
as you can see the same message is read few times but cut.
I wonder what I'm doing wrong...
My port configuration:
port.ReadBufferSize = 4096;
port.BaudRate = 4800;
port.DataBits = 8;
port.Parity = Parity.None;
port.StopBits = StopBits.One;
port.NewLine = "\r\n";
port.ReadTimeout = 1000;
port.ReceivedBytesThreshold = 100000;
And my reading function:
private void processGps(){
while (!closing)
{
//reconnect if needed
try
{
string sentence = port.ReadLine();
//here print the sentence
//analyze the sentence (this takes some time 50-100ms)
}
catch (TimeoutException)
{
Thread.Sleep(0);
}
catch (IOException ioex)
{
//handling IO exception (some info on the screen)
}
Thread.Sleep(200);
}
}
There is some more stuff in this function like reconnection if the device is lost etc., but it is not called when the GPS is connected properly. I was trying
port.DiscardInBuffer();
after some blocks of code (in TimeoutException, after read.)
Did anyone had similar problem? I really dont know what I'm doing wrong.. The only way to get rig of it is removing the last Sleep.
For all those who have similar problem. The first issue was about overflowing the buffer. I had 4096 size of buffer and the data was just flowing trough it so I was reading corrupted sentences. Now I read all buffer at once and analyze it. First sentence is sometimes corrupted, but the rest is ok.
The second thing was the device issue. Tom Tom MkII sometimes loses connection with the device. I had to restart the GPS and find it again in Bt devices list.
Regards
There's nothing in your post to say how you are doing handshaking.
Normally you would use software (XON/XOFF) or hardware (e.g. RTS/CTS) handshaking so that the serial port will tell the transmitting to stop when it is unable to receive more data. The handshaking configuration must (of course) match the configuration of the transmitting device.
If you fail to configure handshaking correctly, you may get away with it as long as you are processing the data fast enough - but when you have a Sleep, data may be lost.