Interruption

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- 30th December 2009, 03:25
ciroman

Interruption

Hello everyone, again!

This time I'm wondering if there is any way to have an event(like a button press) interrupt the code and go to a line label at any time?

The problem with my code is that the controller only checks for the button press after that pause. That pretty much means that you have to hold down the button to get the right timing in order for the moving LEDs to switch direction(which is what my code is about). So is there any way to interrupt the program at ANY time and then point it at a line label to continue there?

this is my code:

Code:

x var byte switch var bit TRISA = 1 TRISC = 0 switch = 1 mainloop: x = 1 loop: PORTC = x pause 500 if switch = 1 then if PORTA.3 = 0 then switch = ~switch goto loop endif if x == 8 then goto mainloop else x = x << 1 goto loop endif else if PORTA.3 = 0 then switch = ~switch goto loop endif if x == 1 then x = 8 goto loop else x = x >> 1 goto loop endif endif
- 30th December 2009, 05:37
mackrackit

Look at interrupt on change normally on PORTB.
- 30th December 2009, 11:58
ciroman

We'll I've got a premade board - The PICKit 2 so the button is on the PORTA.3 pin - just like in the program. Is there no way to do it with that pin?
- 30th December 2009, 13:58
mackrackit

Check the data sheet and see what that pin can do. If it has ADC then with some imagination you could do an ADC interrupt.
But just change things around to use an interrupt pin. That is what they are for.
- 30th December 2009, 15:03
Acetronics2

Hi,

My crystal ball says ...

" Pickit2 with a ready made demo card means a 16F690 " ...

RA.3 shows an Interrupt on change feature ...

soooo ... just use it !!!

Alain

PS: try to give SOME MORE INFOS if you have further questions ...
- 30th December 2009, 22:35
Art

An interrupt is overkill for this, and not the typical way to handle the problem at all.
I'd use a counter to have your button checked every 10ms, and LED routine run every 500ms like this.
and you get to save the interrupt for when it's actually needed.

Code:

x var byte direction var bit timerbyte var byte TRISA = 1 TRISC = 0 x = 1 loop: PORTC = x pause 10 timerbyte = timerbyte + 1 IF PORTA.3 = 0 then IF direction = 0 THEN direction = 1 ELSE direction = 0 ENDIF ' direction ENDIF ' button IF timerbyte = 50 THEN timerbyte = 0 ' 500ms has passed if timerbyte = 0 IF timerbyte = 0 THEN IF direction = 0 THEN IF x = 8 THEN x = 1 x = x << 1 ELSE IF x = 1 THEN x = 8 x = x >> 1 ENDIF ' direction ENDIF ' timerbyte goto loop
- 30th December 2009, 22:50
mackrackit

Overkill????

Please explain.
- 30th December 2009, 22:55
Art

Thought I already did.
It's using hardware to do what should and can be done in software.
Like wiring a circuit to turn the pic's power off to turn an LED off.
and developing bad habit at the same time, and not learning anything.
- 30th December 2009, 23:26
mackrackit

Well after you made an edit to your post you have some explanation.

Looping back through the code every so often to check on a button smells like some sort of pasta to me.

Maybe the OP should learn to use the hardware. Then when the code grow to more than a few lines......

Wait a minute. Your joking, right?
Using an interrupt is forming bad habits.
Now I get it.
NOT!
- 31st December 2009, 00:14
Art

When it's not needed, I think it is.
What if the platform didn't support interrupts?
I think using an interrupt when it isn't needed is forming a bad habit.
The loop is happening anyway, and I have one less label in my code.
It's less spaghetti than the original which doesn't run in one single loop.
An interrupt would add more spaghetti in the generated asm to goto 0x04.

This is a simple program, but as it grew, you might need an interrupt for something else.

EDIT; ps I edited to edit the program, but haven't actually run it.
if it has any issue, it still offers a solution.
- 31st December 2009, 00:30
mackrackit

Fair enough.

Good to see all possible solutions and reasons for the solutions.
- 31st December 2009, 00:51
Bruce

I'll give it a shot with a simple ON INTERRUPT version.

Code:

x var BYTE Switch VAR BIT TRISA = $FF TRISC = 0 ANSEL = 0 ' A/D disabled (all digital) ANSELH = 0 IOCA.3 = 1 ' int-on-change enabled for RA3 INTCON = %10001000 ' enable global & int-on-change interrupts Switch = 1 ON INTERRUPT GOTO MyISR mainloop: x = 1 loops: PORTC = x pause 500 if switch = 1 then if x == 8 then goto mainloop else x = x << 1 goto loops endif else if x == 1 then x = 8 goto loops else x = x >> 1 goto loops endif endif GOTO mainloop ' just in case DISABLE MyISR: WHILE PORTA.3=0 ' wait for button release (so we can clear the int flag & be WEND ' sure it interrupts on a high-to-low transition) Switch = ~Switch ' toggle Switch INTCON.0 = 0 ' clear interrupt flag bit RESUME END

There must be ten gozillion ways to do something like this, even without an interrupt, but
it's still handy to at least learn about interrupts.

Note that you could also do something similar by just monitoring the interrupt flag-bit with
global interrupts disabled. You just need to get a tad more creative...;o}

Tap & release the button as fast as you can to see how quickly it reacts.
- 4th January 2010, 18:35
ciroman

Quote:

Originally Posted by Art

An interrupt is overkill for this, and not the typical way to handle the problem at all.
I'd use a counter to have your button checked every 10ms, and LED routine run every 500ms like this.
and you get to save the interrupt for when it's actually needed.

Code:

x var byte direction var bit timerbyte var byte TRISA = 1 TRISC = 0 x = 1 loop: PORTC = x pause 10 timerbyte = timerbyte + 1 IF PORTA.3 = 0 then IF direction = 0 THEN direction = 1 ELSE direction = 0 ENDIF ' direction ENDIF ' button IF timerbyte = 50 THEN timerbyte = 0 ' 500ms has passed if timerbyte = 0 IF timerbyte = 0 THEN IF direction = 0 THEN IF x = 8 THEN x = 1 <- You forgot that if x = 8 and then x = 1 you must go to loop or else x will never be 1 but MORE than one x = x << 1 ELSE IF x = 1 THEN x = 8 <- Same here x = x >> 1 ENDIF ' direction ENDIF ' timerbyte goto loop

I have pointed out some mistakes. Thanks for your code man anyway, cool way to do things, much better than ON INTERRUPT I believe. Don't be too harsh on me guys I've been learning this for less than a week
- 4th January 2010, 20:20
Bruce

Quote:

I've been learning this for less than a week

I would say you're definitely doing good for someone just getting started.

It's nice here since you find so many various ways of doing something, which really
helps one to think outside-the-box. Embedded programming is just creative problem
solving, and you'll find a lot of different creative approaches around here for
sure.

Which one is best for your application is totally up to you.
- 5th January 2010, 06:10
ciroman

Thanks Bruce, you just pointed out the reason why I love programming and why I love programming a micro controller is because you can see the results in real life, not only digitally.

Thanks, really