Thread: Think back. . .

Originally Posted by CornedBee

Such a thing is always hardware-specific. You need a precise timer for that.

Yup. . . I know. I just thought that *maybe* someone knew a way. . . I know the way, the truth and the light. . . no man cometh unto the nanosleep except by Linux.

Originally Posted by swoopy

How about:

Code:

usleep(num_usec);

Is that in DOS????? I remember it not being there. I'll check, though.

Maybe you want to have a look to select(2) man page. You can use select(2) to have a delay in your programs.

Originally Posted by Salem

http://www.versalogic.com/Products/DS.asp?PN=Bobcat
http://sbc.winsystems.com/products/sbcs/index2.html
Step 1 is review the hardware specifications for the boards.

Yup, been there.

Originally Posted by Salem

Step 2 is check with the vendors to find out if they supply any "board support package" for the OS you have chosen.

Done that.

Originally Posted by Salem

If that works, you may find yourself in possession of an API call which permits fine-grained timing.

Which is why I was hoping someone knew a way in DOS to do this. . .

Originally Posted by Salem

If that doesn't work out, then I guess you're going to have to implement your own "programmed delay", say something like

Code:

const int limit = 1000000;
void wait1microsecond ( void ) {
  volatile int i;
  for ( i = 0 ; i < limit ; i++ )
  {
  }
}

Exactly how you calibrate that from board to board is another matter.
Also, do you want to allow for elapsed time in interrupt service routines (for example)?

Basically, that is what I'll end up doing. I'll supply the 'limit' in a config file for the machine. This change, however, is considered a "major change" and will "have to be tested" for it to be accepted. Ever work for a G'ment project? These two small sentences are very very . . . well, you know.

MS DOS did not have any timer specific functions in the OS. I'm quite sure that Dr. DOS won't either if it also runs in real mode.

Several options depending on CPU type, chipset type, etc, etc.

1. Hook a timer interrupt and write a handler that increments a variable and returns the value in a register. Be careful with this b/c on Intel if you hook the incorrect interrupt, you will alter the BIOS time.
2. Program the chipset timer - this could entail any multiple sets of solutions and will differ for all platforms, CPUs, chipsets, mobos, etc.

As this is for an embedded system, I doubt highly you will find anything with timer support.

Originally Posted by Salem

If there is any timer at all on the board (I see some have RTC hardware), then it's perfectly possible to auto-calibrate the delay loop in the startup code.

Key word ==>some<==. It cannot be assumed that there is a RTC. Also, some of these actaully have a RTC interface - the docs state that the RTC can be connected externaly. That is not an option for me.