Hello everyone,
I know there is a build in real time clock inside the computer
and I know it's possible to use this clock when you write a program on Assembler(using an interupt that I don't remember at the moment),is there a way to use the real time clock
while programing on VC++ ?
(I use VC++ 6.0 with the 6th service pack instaled)


Andrei

Yes, you get clock functionality from library <ctime> (or maybe it's still <time.h> in VC++ 6)
See here for a quick reference.

Check your MSDN help information in VC++ for what's actually supported in that compiler.

Consider moving into the 21st century with newer versions. VC++ 2008 Express is a freebie.

Regrettably, all <ctime/time.h> stuff does not bear a relation to the computer Real Time Clock device. Moreover, you can't directly access RTC in standard Windows user mode.

In what modes can I acces it?

I think partially on device driver level or lower (HAL).

Did you need so low level really? The Windows without (as usually third-party and commercial) special software is not a real-time system. Your programs have no direct access to ALL hardware (except CPU in user mode ) on Windows installations. Didn't you know that?

Why you need RTC direct access? May be Windows API or even RTL stuff is enough for your task?..

Well, ofcourse I know that from win 2000 and upwards the acces to the ports is blocked,
but I have a driver that opens the access(and I already tested it many times while working with the parallel port),so I do have access to the hardware.
I need a real time clock to generate accurate PWM for a robot...

It's not a true RTC access (even with RTC driver) because Windows threads sheduling adds unpredictable delays for your robot control process irrespective of its priority.
That's why Windows is not RT system...

For hi-res timers, you may want to have a look at the following (100us timer period):
http://www.codeproject.com/KB/system...imeModule.aspx

What's the frequency of the PWM? Are you interfacing to RC servos?

Ok,first of all I want to thank everyone for their help,thanks everyone!

Now,dougey83, thank you for the program,did you try it? How accurate is it?
How much windows distortes the timers accuracy?(oh,and this time I use an H-bridge and regular DC motors,not servos,if it's possible I want to generate PWM with frequancies of 1 to few Khz).
ArkM,you didn't pay attention,I said a driver that gives me access to ports(in other words,it allows me to access hardware),not a RTC driver...

could you not use a Hardware clock to do the timing for you?

Chris