Non obstructive wait

Glenn Patton

Hi All,
I am trying to perfect a bit of test code for a device we have updated (amongst other thing replaced a 9 Way with USB) I want to a method of waiting for a command to come back,the routine waits while there are no bytes in the buffer and the time is less the value passed to it. NbDataToWait is a bit vague I would prefer to wait for '>' come back but can't seem to think of a way to do it quickly!
public int WaitForData(int NbDataToWait, int Timeout)
{
int timeWaited = 0;
int timeToWait = 1; // 1 ms

// && there is no > in reply
while (timeWaited < Timeout && myComPort.BytesToRead < NbDataToWait)// && myComPort.BytesToRead(">"))
{
timeWaited += timeToWait;
lblwhere.Text += ".";
System.Threading.Thread.Sleep(timeToWait );
}

return timeWaited;

}
/* public int WaitForDataOK(int NbDataToWait, int Timeout)
{
int timeWaited = 0;
int timeToWait = 1; // 1 ms

// && there is no > in reply
while (timeWaited < Timeout && myComPort.BytesToRead > 0)
{
timeWaited += timeToWait;
lblwhere.Text += ".";
System.Threading.Thread.Sleep(timeToWait);
}

return timeWaited;

}
*/
UPDATE:: I believe I need to wait for a >

14 Replies

Know the answer? Post it — somebody with the same question will find it here.

Sam Hobbs14y ago
Then it is not clear whether you can get the best possible help here. For help with the C# language and .Net libraries, continue requestiong assitance here. If the people here cannot help then you, based on the question, what type of forum you need to look for.
Glenn Patton14y ago
Well I know most of my isssues tend to be the way I handle Windows Coding rather than the actual nuts & bolts of Serial Comms, Vulpes (on a previous board!) has dug me out of more than one hole in the past regaurding C# really it is just the nuts and bolts of C# and Windows I don't get.
Sam Hobbs14y ago
I do not know. Of course you are welcome to ask here but you know that most members here are not the most experienced with serial communications.

There is a forum in the MSDN forums that is for asking where to ask questions. You could try asking there where is a good place to ask your questions.

I tried a search. There appears to be possibilities there.

Serial communications is older technology and newsgroups are also older technology. There is certainly many answers in the newsgroups and Google Groups still has newsgroups in it. So if this link works then it will help you find newsgroups.
Glenn Patton14y ago
Hi Sam,

I really need a Serial Class specialty area for these questions, for the hardware side www.lvr.com is good, MSDN are quite good (if at times not quite right) can you suggest a board that is better for Serial Comms stuff that is actually in use.
Most of my questions do tend to be on timing and interrupts and the related.

Glenn
Sam Hobbs14y ago
As for what forum to use, let me say that it would be more appropriate to use one of the other forums. This is not a C# Language question. There is a forum for .Net; perhaps that is where this belongs.

Certainly it would seem that the UI is not relevant, but unfortunately there are more non-UI things that depend on the UI than probably should. If you are asking how to interface with the UI then that would depend on the UI.
Glenn Patton14y ago
Hi, I have encounter another hardware fault on the board will fix it and get back to tomorrow, Thanks for the help! Glenn
Glenn Patton14y ago
Thanks for that WaitForSingleObject never seen it before, Will play tomorrow!
Glenn Patton14y ago
Thanks for that WaitForSingleObject never seen it before, Will play tomorrow!
Glenn Patton14y ago
WaitForSingleObject only seen it in passing I will play more tomorrow too tired now!!
Sam Hobbs14y ago
What you should do is to create a timer for the timeout. I assume that the data is being read asynchonously. So there is an event somewhere that your program needs to wait for. You can use the WaitForMultipleObjects method or something similar to wait for both events; the timer and data. Then when the wait completes, check to see which event it is; if it is the timer then you know to give up.

Actually, WaitForSingleObject has a timeout. That should be very easy to use. Your problem depends o using asynchronous reads which can waited on using WaitForSingleObject with a timeout. That would work, correct? It sounds like an easy and effective solution.
Glenn Patton14y ago
I will give it ago as soon as I have repaired the board!!
Glenn (thanks)
Vulpes14y ago
My previous suggestion keeps on looping while there are still bytes to be read (BytesToRead > 0) or until the timeout has been reached if earlier.

However, if you're reading the bytes elsewhere and placing them in textBox1, then you could stop looping when ">" has been read if that's sooner than the other two conditions, as follows:

public int WaitForData(int Timeout)
{
Stopwatch sw = Stopwatch.StartNew();

while(sw.ElapsedMilliseconds < Timeout && myComPort.BytesToRead > 0 && textBox1.Text.IndexOf(">") == -1)
{
lblwhere.Text += ".";
System.Threading.Thread.Sleep(1); // sleep for 1 millisecond
}

int elapsed = (int)sw.ElapsedMilliseconds;
sw.Stop();
return elapsed;
}
Glenn Patton14y ago
I believe I need to wait for a > or an OK from the board won't that just wait until something comes back (.BytesToRead is greater than 0) the code below was from an idea I had for search the return of a > or OK (I guess).
private void button1_Click(object sender, EventArgs e)
{
string TextContaing;
int LocationOf;

TextContaing = textBox1.Text;
MessageBox.Show(TextContaing);

LocationOf = TextContaing.IndexOf(">");
if (LocationOf > 0)
{
MessageBox.Show("Got One! "+LocationOf.ToString());
}

}
Vulpes14y ago
I'd try and use the System.Diagnostics.Stopwatch class for something like this:

I assume the bytes in the buffer are being read elsewhere. To be able to tell whether a ">" has been read or not, you need to access the buffer where you're storing those bytes. The following ignores this for now and just waits until all the bytes have been read or the timeout has occurred:

using System.Diagnostics;

// .....

public int WaitForData(int Timeout)
{
Stopwatch sw = Stopwatch.StartNew();

while(sw.ElapsedMilliseconds < Timeout && myComPort.BytesToRead > 0)
{
lblwhere.Text += ".";
System.Threading.Thread.Sleep(1); // sleep for 1 millisecond
}

int elapsed = (int)sw.ElapsedMilliseconds;
sw.Stop();
return elapsed;
}