PIC : how to make multiple non-blocking delays with one timer

Absolutely right. What Bruno has done is to combine the scheduler and despatcher into a single ISR. It would make better use of resources and make the system more responsive if only the scheduler were in the ISR.

Ian

This is something I would like to build. It will not be a timer, it will count objects passing a point.

I have several chips on order: 7447, 7448, 74192, etc... I'm looking for something I can work up on a bread board and then possibly put on a small project PC board from Radio Shack.

It will eventually go into a paintball marker that has been built to look like the Pulse Rifle from Aliens.

First off, join the 21st Century and use 'HC parts ;-)

...Jim Thompson

At the suggested speeds, the CD4000 series would be a better option. You don't need to worry as much about the voltage regulation.

Thanks, but I need a display. Preferably 3 digits using 7-segment LEDs.

I have a schematic from an OLD Radio Shack book that uses a 555 to drive a 7490 that dumps into either a 7447 or 7448 and then into a

I'm going to use an IR LED emitter and receiver to count objects passing a point (piantballs leaving the barrel or hopper).

In article , Bob Monsen wrote: [....]

I assume that on a PIC, you can't push a value onto the stack so as to force the non-interrupt level to call the desired routine. If this is true then using the busy loop idea is a good one. Without it, your timed routines will be harder to code.

don't need to worry as much about the voltage regulation.

What ever it takes... I just need a schematic.

Really, I'm not looking to count more than 15 objects per second...

Check out the 74HC192. It may be the right part for you.

Do you want the up-down feature too at this time?

It makes a difference in what I'd suggest.

Counting down is more inportant than presetting the max count.

I don't know about the larger PICs, but for the 12 and 16 series, the call stack is in hardware, and is not accessible to the programmer (it is also limited to 8 calls, and wraps. Sigh...).

The 18 chips, have larger stacks. Typically perhaps 20 deep (still not large to handle anything other than call/return operations). You can also access the 'top of stack' value, and the stack pointer. This allows you to write a software stack, to extend the existing stack if required. However it takes several instructions to access a single value (typically three read or write operations on the larger chips - the stack is 21 bits wide on these), then the I/O to the pointer.

Best Wishes

"Ken Smith" a écrit dans le message de news: dums6n$3fl$ snipped-for-privacy@blue.rahul.net...

Yes, push and pop instructions do not exist on pic MCUs, they have to be made by software. Otherwise, cheating with stack return values is a good assembler trick, but it would be risky to use it with a high-level language as C because low-level registers are controlled by compiler.

Bruno

Some of the 8051 C compilers have special "not really C" stuff added to them to make such stuff safe to do. They usually appear as some sort of magic variable.

thatr method has disadvantages too, what if the routine that's being called should be uninterruptable?

Bye. Jasen

RoutineName: CLR EA ... etc ...