Re: Generating a short delay (a few ms) - C / C++ / MFC Discussion Boards

LittleYellowBird3-Nov-02 23:58

3-Nov-02 23:58

I'm trying to generate a short delay of just a few ms, which I need because I am controling a box on the serial port which is very slow and the input is un-buffered so I need to pad the data.

I am using Sleep(x), where x is the number of ms. However, I get a much longer delay than I need, ie Sleep(1) gives me 70ms!

Anyone got any ideas of how I can generate a short delay reliably?

Thanks,

Ali

Re: Generating a short delay (a few ms)

Vagif Abilov4-Nov-02 0:30

Vagif Abilov

4-Nov-02 0:30

You can try Sleep(0), it causes the thread "to relinquish the remainder of its time slice to any other thread of equal priority that is ready to run."

Vagif Abilov
MCP (Visual C++)
Oslo, Norway

Hex is for sissies. Real men use binary. And the most hardcore types use only zeros - uppercase zeros and lowercase zeros.
Tomasz Sowinski

Re: Generating a short delay (a few ms)

LittleYellowBird4-Nov-02 2:21

LittleYellowBird

4-Nov-02 2:21

Thanks for the suggestion, I'm not sure it will give consistent enough results - I'll look in to it though.

Thanks,

Ali

Re: Generating a short delay (a few ms)

Gary Kirkham4-Nov-02 11:26

Gary Kirkham

4-Nov-02 11:26

You didn't say what operating system you were using. I doesn't answer your question, but you may find the following article interesting...

http://www.codeproject.com/system/simpletime.asp

Gary Kirkham

A working Program is one that has only unobserved bugs

Re: Generating a short delay (a few ms)

LittleYellowBird5-Nov-02 3:15

LittleYellowBird

5-Nov-02 3:15

Looks like an interesting article, thanks for the tip.

Cheers,

Ali

Re: Generating a short delay (a few ms)

viliam4-Nov-02 0:33

viliam

4-Nov-02 0:33

I am afraid there is no way how to suspend process on accurate time.
(Windows are not real - real-time system)
The easiest way is use traditional way – run some loop
(and be on appropriate priority)
And check time...
Something like:
.
.
dwA = GetTickCount();
while(1)
{
dwB = GetTickCount();
if( (dwB-dwA) >= dwTimeout)
break;
}

This is not nice way but sometime can help.
Anyway times about 1 ms are probably unreachable.
Viliam

Re: Generating a short delay (a few ms)

LittleYellowBird4-Nov-02 2:18

LittleYellowBird

4-Nov-02 2:18

Using GetTickCount() is a great idea. I just checked the help and it returns the number of ms since start up, so as you suggest I can use it in a loop to make a basic timer.

I agree that 1 ms is impractical but if I try for 1 ms and get 2 ms or 3ms or even 4ms, that woud be far better than 70+ ms!

Thanks for the help,

Ali

Re: Generating a short delay (a few ms)

Brigg Thorp4-Nov-02 2:28

Brigg Thorp

4-Nov-02 2:28

One thing you have to watch out for. If you keep your computers on all the time, the rollover of the time could effect your calculation (e.g the start time could be greater than the end time). You just have to put in checking for this.

Brigg Thorp
Software Engineer
Timex Corporation

Re: Generating a short delay (a few ms)

LittleYellowBird4-Nov-02 3:02

LittleYellowBird

4-Nov-02 3:02

Good point, as you say pretty easy to check for, I'll make sure I do.

Thanks,

Ali

Re: Generating a short delay (a few ms)

includeh104-Nov-02 1:10

includeh10

4-Nov-02 1:10

as i know, serial port needs a thread (call it thread A) to read data.
u say "delay", delay what? for what?
i assume that u want "delay" (by Sleep) main thread (parent thread of thread A) to active Thread A. this is not correct in concept, the 70ms must be got from Thread A, the time is meaningless, just forget it.

only choice i think is to set a timer (few ms) in main thread for delay, then kill the timer.

includeh10

Re: Generating a short delay (a few ms)

LittleYellowBird4-Nov-02 2:10

LittleYellowBird

4-Nov-02 2:10

includeh10 wrote:
u say "delay", delay what? for what?

What I need is a delay between sending bytes because the receiving device is too slow and cannot buffer data coming in. If I send bytes too quickly they get ignored. But if I have really big delays then it takes ages to set up.

It looks like this is not possible, not sure what I am going to do.

Thanks for the advice,

Ali

Re: Generating a short delay (a few ms)

includeh104-Nov-02 2:25

includeh10

4-Nov-02 2:25

i used communication port for years, do u use a event to check if sending buffer is empty?

includeh10

Re: Generating a short delay (a few ms)

LittleYellowBird4-Nov-02 3:09

LittleYellowBird

4-Nov-02 3:09

includeh10 wrote:
do u use a event to check if sending buffer is empty?

Yes, I send a block of data. I can see that the sending buffer is empty. Then I want to leave a gap of 1 or 2 ms to let the receiving device process the data before I send the next block of data.

If I do not leave a gap at all, then the receiving device ignores the first block of data and it is lost.

If I leave a big gap like 70ms to 100ms, I can't send the data quickly enough, because most of the time is used up by the gaps.

I think I may be able to use GetTickCount to create a basic timer, (see above reply). I think I will try that.

Thanks for your help,

Ali

Re: Generating a short delay (a few ms)

includeh104-Nov-02 4:26

includeh10

4-Nov-02 4:26

communication port is not an easy job, u need to generate a good process in one app then for forevere (next apps).
i suggest u use 2 threads (sibling threads). one thread keeps all sending data in a buffer, another one is used for receiving data and deals with events.
u can use sleep between sibling threads to control working process.
if use many threads, make sure they are terminated properly (i used over 100 threads in one app). do not use CloseHandle() etc to interrupt threads, especially buffering threads. let threads exit natually, otherwise u may see exceptions often.

includeh10

Re: Generating a short delay (a few ms)

LittleYellowBird5-Nov-02 3:18

LittleYellowBird

5-Nov-02 3:18

includeh10 wrote:
communication port is not an easy job

Yes, thats true, and to be honest I have only one thread at the moment so that is obviously not helping. Looks like its time to look at threads!

Thanks for the advice,

Ali

Re: Generating a short delay (a few ms)

Roger Allen4-Nov-02 7:09

Roger Allen

4-Nov-02 7:09

I did something similar for a data collection thread that has to get spectra from a Diode array detector on set intervals. The way I did it was to the set thread priority very high (TIME_CRITICAL), so when the Sleep() completed, that thread was given control again. As it spent most of its time in a sleep() state it did not have any adverse effect of system performance.

Some of the oce envolved was:

RunThread->SetThreadPriority(THREAD_PRIORITY_TIME_CRITICAL) ;


	FILETIME time1;
	FILETIME time2;


	::GetSystemTimeAsFileTime(&time1) ;		// get the current time
	
	while (...)
		{
		::GetSystemTimeAsFileTime(&time2) ;		// get the current time
		delay = (m_spectra_frequency * spectra_collected) - CalculateElapsedTime(&time1, &time2) ;
		if (delay >= 0.001)
			Sleep((unsigned long)(delay * 1000.0)) ;
		}




double CalculateElapsedTime(FILETIME *start, FILETIME *current)
{
	double	elapsed_time ;
	__int64	st ;
	__int64	ct ;
	__int32	*p ;

	p = (__int32*)&st ;
	*p++ = start->dwLowDateTime ;
	*p = start->dwHighDateTime ;
	//st = (start->dwHighDateTime << 32) + start->dwLowDateTime ;
	p = (__int32*)&ct ;
	*p++ = current->dwLowDateTime ;
	*p = current->dwHighDateTime ;
	//ct = (current->dwHighDateTime << 32) + current->dwLowDateTime ;
	elapsed_time = (double)(ct - st) ;
	elapsed_time /= 10000000.0 ;	// convert from 100ns intervals to seconds
	return elapsed_time ;
}

It may be of use

Roger Allen
Sonork 100.10016

I have a terminal disease. Its called life!

Re: Generating a short delay (a few ms)

LittleYellowBird5-Nov-02 3:29

LittleYellowBird

5-Nov-02 3:29

Thanks for the advice. Believe it or not I've got away with just one thread in all my apps up to now! But it looks like I cannot run away any longer, now is the time to look at threads.

I think I can see what you are explaining, its nice to have the code snippet to look at - I'll give it a go.

If you see some more questions about threads from me in the coming days you'll know it hasn't gone well! Smile | :)

Thanks again,

Ali

Change data format from CString to int

ooosawaddee33-Nov-02 23:35

ooosawaddee3

3-Nov-02 23:35

If I have this below CString data and I want to change it format to int.

Example:
CString data_str = "1487";
int data_int;

I want

data_int = 1487

Do you know how to do that?

Re: Change data format from CString to int

ian mariano3-Nov-02 23:43

ian mariano

3-Nov-02 23:43

Sometimes the C runtime comes in handy: atoi()[^]

"The greatest danger to humanity is humanity without an open mind."
- Ian Mariano - http://www.ian-space.com/

Re: Change data format from CString to int

RChin3-Nov-02 23:48

RChin

3-Nov-02 23:48

use:

data_int = atoi( (LPCTSTR)data_str );

or even better use:

data_int = _ttoi( (LPCTSTR)data_str ); // unicode safe

MSI files problem

Anthony B.3-Nov-02 23:25

Anthony B.

3-Nov-02 23:25

I have used Visual Studio Installer to produce some MSI files
to install my applications.

I some PCs, where only WINNT or WIN2K OS is installed (MS office
not installed)the MSI file cannot be executed.

Does someone knows which application or DLL must be installed in
the target machine in order to allow the MSI file execution ???

Thank a lot !!!

Re: MSI files problem

ian mariano3-Nov-02 23:33

ian mariano

3-Nov-02 23:33

The MSI installer must be installed on the machine you are targeting.

Redistributable v1.2 for Windows 95, Windows 98, and Windows ME[^].

The MSI installer comes automatically w/Win2k and higher.

"The greatest danger to humanity is humanity without an open mind."
- Ian Mariano - http://www.ian-space.com/

Re: MSI files problem

Anonymous6-Nov-02 12:53

Anonymous

6-Nov-02 12:53

I believe in your properties area for your project you can say to compile into a msi or setup.exe with installer support.. then it will output a .msi plus a setup.exe etc... then you have to distribute all the files in your output dir..

Comparing VC++.net standard and VS.net professional

Anonymous3-Nov-02 23:30

Anonymous

3-Nov-02 23:30

Hello all
according to ms features list, I have checked out the comparison table and it seems to me that vc++.net standard is missing the following features:

1) Enhanced professional C++ Optimizing Compiler
Build and deploy professional-quality applications with the industry's leading C++ Optimizing Compiler, which generates the smallest and highest performing executables. Now with Whole Program Optimization technology.

2 Enhanced advanced application wizards
Easily generate advanced C++ projects with professional-level application wizards for MFC ISAPI dynamic-link libraries (DLLs), Custom Visual Studio Wizards, and more.

3 Built-in support for additional programming languages
With support for multiple programming languages, you can easily program in the language of your choice and integrate the code from any other language.

4 Remote Debugging
Extend your debugging capabilities by stepping seamlessly into remote processes, including XML Web services.

5 SQL Debugging
With the Visual Studio .NET debugger, you can debug Microsoft SQL™ Server stored procedures, functions, and triggers in much the same way that you debug other kinds of scripts or programs.

6 Crystal Reports
Build rich interactive reports for Windows-based, Web-based, and mobile applications, as well as XML Web services.

7 Visual Database Tools
Design stored procedures, indexes, tables, triggers, user-defined functions, and other database elements visually. In the Visual Studio .NET Professional Edition, these design capabilities are limited to the SQL Server Desktop Engine.

8 Extended Stored Procedure DLLs
Create SQL Server extended stored procedures (XPROC) in C++ with the Extended Stored Procedure DLL project template.

Now, as I am planning basically to write freeware/shareware applications it seems to me that the Vc++.net standard fits my needs. In particular 2) to 8) seem to me options i reasonably will use very little.
As far as the 1) is concerned vc++.net standard offers a
Non-optimizing C++ Compiler to
Build and deploy C++ applications with performance and size characteristics appropriate, as MS tells, for hobbyist, student, and beginning programmers.
Now i have tested some siple projects (ie: wizard generated for MDI/SDI and dialog applications) and reported (working on windows XP HE) EXE sizes like the folllwing (release versions):

-SDI: close to 300 Kb
-MDI: close to 370 Kb
-DLG based appl.: close to 156 Kb

Which are the typical EXE sizes for similar projects generated and, i guess, optimized/tweaked by the VS.NET compiler?

Besides that, although the MS features comparison list pointing out the Non-optimizing C++ Compiler of this edition, i can find:

a) an 'optimize the whole program' option under the general projects settings page

b) an 'optimizazion page' under c/c++ with: 'enable independent optimizazions', 'processor optimizazions' and 'optimize for windows applications'

c) Linker/optimizazion

enable COMDAT reduction
optimize for win 98
functions order

I wonder if working on all and/or some of the above parameters i could get better EXE sizes and/or other useful optimizations, of course without troubles (otherwise i will leave those options like they are automatically set up by the IDE) Wink | ;)

any help/tip/info will be greatly appreciated
thanks in advance

/MD and other c/c++ code generation options

Mondrianx3-Nov-02 23:00

Mondrianx

3-Nov-02 23:00

Hello all
with reference to VC++.NET
i'd like to figure out a little more deeply the following options (under project settings/c/c++ code generation options page):

runtime library:
/MD[d]
/ML[d]
/MT[d]
/LD[d]

I don't know much about 'threads', i have just noticed that when i select an 'MFC statically linked application', the compiler puts for me /MT[d for debug version] and puts /MD for an 'MFC linked as a shared DLL' project.

I have read the compiler help about these parameters but it isnt' actually much clear, so any tip/info will be greatly appreciated
I especially wonder if, say, i can 'forget' almost everything about these options as long as i will be just selecting 'statically linked MFC projects' (ending in /MT) or 'dynamically linked ones (ending in /MD) or, even if the wizard inserts, as pointed out below, them automatically, there are particular situation needing a further tweaking.

thanks in advance

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