PIC16F877A - Timer0 won't interrupt

Hello all,

I've been struggling with a, for a not-picbasic-newbie (which I am! :( ), simple problem. I'm trying to let a LED blink on the overflow rate of timer0. Unfortunately I wasn't very succesfull.

When I run the following code (I know the LED won't blink with this, but that's step 2)

Code:

define loader_used 1 define osc 20 led var portc.1 ;LED is connected on PortC.1 wsave var byte $20 system ssave var byte bank0 system psave var byte bank0 system Goto main define INTHAND tmroverflow asm tmroverflow movwf wsave swapf STATUS, W clrf STATUS movwf ssave ;Interrupt movf PCLATH, W ;Routine movwf psave ;with Save function bsf _led ;Put on LED movf psave, W movwf PCLATH swapf ssave, W movwf STATUS swapf wsave, F swapf wsave, W bcf intcon,2 ;Clear Interrupt Flag retfie ENDASM main: INTCON = %10100000 ;GIE enabled, T0IE enabled OPTION_REG = %00000101 ;Prescaler on TMR0 rate 1:32 goto loop loop: goto loop ;Wait here for interrupt

When I run it in debug mode, the compiler goes insane and gives me mismatched address errors after the timer didn't respond for some time (the watchdog timer is off, so it isn't him who's complaining :) )
I think that my mistake is in the INTCON and/or the OPTION_REG, but experimenting with this values didn't helped me further neither.
The "save" function is O.K asfar as I can see, since it's straight out of the manual!! ;)

All it need to do for step 1 is to light the LED...

So if someone sees the problem right away, and I'm sure there will be many, please help this desperate newbie! I will be very gratefull!

Cheers,

William

I don't see anything for a TRISC.1 = 0

Code:

define loader_used 1 define osc 20 led var portc.1 ;LED is connected on PortC.1 ledcnt var word wsave var byte $20 system ssave var byte bank0 system psave var byte bank0 system Goto main define INTHAND tmroverflow asm tmroverflow movwf wsave swapf STATUS, W clrf STATUS movwf ssave ;Interrupt movf PCLATH, W ;Routine movwf psave ;with Save function inc _ledcnt ;increment the counter movf psave, W movwf PCLATH swapf ssave, W movwf STATUS swapf wsave, F swapf wsave, W bcf intcon,2 ;Clear Interrupt Flag retfie ENDASM main: INTCON = %10100000 ;GIE enabled, T0IE enabled OPTION_REG = %00000101 ;Prescaler on TMR0 rate 1:32 Output LED loop: led = ledcnt.7 ;make the led follow bit 7 of ledcounter goto loop ;Wait here for interrupt

A couple of changes. If you don't see the LED blink, turn up the prescaler and/or use a slower oscillator for test. At least you should see it work.

Typo or I missed that instruction

Quote:

Originally Posted by skimask

[code]

incf _ledcnt ;increment the counter

Hi,

Skimask I think it should be incf and is a simple typo.

Quote:

Originally Posted by sougata

Hi,

Skimask I think it should be incf and is a simple typo.

Yep, should be, and is......then again, it is Friday the 13th....maybe my keyboard is playing em no skcirt

Interrupts and the MSC Debugger don't get along very well together.

You must DISABLE debugging in any interrupt routines.

Code:

DISABLE DEBUG asm tmroverflow movwf wsave ... ... retfie ENDASM ENABLE DEBUG

For an 877, you should use $70 for the wsave address.

OPTION_REG = %00000101 sets the prescaler to 1:64. (comment says 32)

and, like skimask said ... set the LED's pin to output.

Also a working example on MELABs website
http://www.melabs.com/resources/samples/pbp/asmint.bas
(maybe you got your start for yours there? I did not check if they are similar)

Thanks all for your responds, will try them out on monday, it's weekend now. But thank you all very very much :)!!!

It's working perfectly!!! Thanks for the help! :)

Cheers,

William

Hello all!!
An update and help request on my program:

Code:

define loader_used 1 define osc 20 ;---Defining Variables--- wsave var byte $70 system ssave var byte bank0 system psave var byte bank0 system count0 var byte bank0 system count1 var byte bank0 system count2 var byte bank0 system count3 var byte bank0 system count4 var byte bank0 system count5 var byte bank0 system hulp0 var byte bank0 system hulp1 var byte bank0 system hulp2 var byte bank0 system whulp var byte bank0 system pclhulp var byte bank0 system sthulp var byte bank0 system ;---Zeroing registers--- count0 = 0 count1 = 0 count2 = 0 count3 = 0 count4 = 0 count5 = 0 hulp0 = 0 hulp1 = 0 hulp2 = 0 whulp = 0 pclhulp = 0 sthulp = 0 STATUS.0 = 0 Goto main ;Skip interrupt routine define INTHAND int DISABLE DEBUG asm ;---Save W, STATUS and PCLATH--- int movwf whulp swapf STATUS, W clrf STATUS movwf sthulp movf PCLATH, W movwf pclhulp ;---Clock program--- incf count0, F movwf count0 call check movf count0, W btfss STATUS,0 goto eindafwerking incf count1, F movwf count1 call check movf count1, W btfss STATUS,0 goto eindafwerking incf count2, F movwf count2 call check movf count2, W btfss STATUS,0 goto eindafwerking incf count3, F movwf count3 call check movf count3, W btfss STATUS,0 goto eindafwerking incf count4, F movwf count4 call check movf count4, W btfss STATUS,0 goto eindafwerking incf count5, F movwf count5 call check movf count5, W btfss STATUS,0 goto eindafwerking ;---Restore W, STATUS and PCLATH--- eindafwerking movf pclhulp, W movwf PCLATH swapf sthulp, W movwf STATUS swapf whulp, F swapf whulp, W bcf intcon,2 retfie ;---Check function for counts to be 99h maximum (NOT USED YET)--- check return ENDASM ENABLE DEBUG main: INTCON = %10100000 ;GIE enabled, T0IE enabled OPTION_REG = %00000111 goto loop loop: goto loop ;Wait here for interrupt

The program before (with the LED) was to time it on 1 millisecond, the final program (which isn't this one ofcourse ;) ) is for measurement purposes.

Test step 2:
What I try to do here is to make a counter, that increments count0 when the timer overflows, then when count0 is full, it increments count1 etc etc. Atleast... it should do that....

The things i tried to make it work:
- Reset the C flag of STATUS, only this made only count0 to run.
- Switched , W with , F and vice versa (example: STATUS, W becomes STATUS, F)

A colleague told me to make some own save location (pclhulp, whulp and sthulp). I'm not sure if this is okay...

If someone could help me out again, I will be very gratefull (again!!). :)

Cheers,

William

(Excuse me for the dutch labeling, it shouldn't be be much of a problem i guess :) )

/EDIT:

Allrightey I fixed the problem myself! Yay ^^!

Code:

define loader_used 1 define osc 20 ;---Defining Variables--- wsave var byte $70 system ssave var byte bank0 system psave var byte bank0 system count0 var byte bank0 system count1 var byte bank0 system count2 var byte bank0 system count3 var byte bank0 system count4 var byte bank0 system count5 var byte bank0 system hulp0 var byte bank0 system hulp1 var byte bank0 system hulp2 var byte bank0 system whulp var byte bank0 system pclhulp var byte bank0 system sthulp var byte bank0 system ;---Zeroing registers--- count0 = 0 count1 = 0 count2 = 0 count3 = 0 count4 = 0 count5 = 0 hulp0 = 0 hulp1 = 0 hulp2 = 0 whulp = 0 pclhulp = 0 sthulp = 0 STATUS.2 = 0 Goto main ;Skip interrupt routine define INTHAND int DISABLE DEBUG asm ;---Save W, STATUS and PCLATH--- int movwf whulp swapf STATUS, W clrf STATUS movwf sthulp movf PCLATH, W movwf pclhulp ;---Clock program--- incf count0, F movf count0, W call check movwf count0 btfss STATUS,2 goto eindafwerking bcf STATUS,2 incf count1, F movf count1, W call check movwf count1 btfss STATUS,2 goto eindafwerking bcf STATUS,2 incf count2, F movf count2, W call check movwf count2 btfss STATUS,2 goto eindafwerking bcf STATUS,2 incf count3, F movf count3, W call check movwf count3 btfss STATUS,2 goto eindafwerking bcf STATUS,2 incf count4, F movf count4, W call check movwf count4 btfss STATUS,2 goto eindafwerking bcf STATUS,2 incf count5, F movf count5, W call check movwf count5 bcf STATUS,2 goto eindafwerking ;---Restore W, STATUS and PCLATH--- eindafwerking movf pclhulp, W movwf PCLATH swapf sthulp, W movwf STATUS swapf whulp, F swapf whulp, W bcf intcon,2 retfie ;---Check function for counts to be 99h maximum (NOT USED YET)--- check return ENDASM ENABLE DEBUG main: INTCON = %10100000 ;GIE enabled, T0IE enabled OPTION_REG = %00000111 goto loop loop: goto loop ;Wait here for interrupt

What I did wrong:
- I switched the movf and the movwf instructions!
- Checked the wrong bit, it checked the carry flag (Status.0) instead of the Zero flag (Status.2)

I feel so noobish >)

Quote:

Originally Posted by WishMaster^

I feel so noobish >)

Really? Well...how many 'noob's' can say they fixed a problem on their own.
I do believe you've done graduated out of the noob class...
Now go let all the smoke out of a PIC to celebrate! :D

1 Attachment(s)

Quote:

Originally Posted by skimask

Really? Well...how many 'noob's' can say they fixed a problem on their own.
I do believe you've done graduated out of the noob class...
Now go let all the smoke out of a PIC to celebrate! :D

I can count myself as a real rookie now!! :D

Now that my program is growing, I encountered a new problem.
The program is now some sort of stopwatch with 1 control button on portb.4.
The problem is, that when I press the button, the timer won't start and it goes straight to "The time is: 00,00"

What do I miss here?

anyone? ^^

Cheers,

William

/EDIT While I studied the behaviour of the program, I saw something odd... When i press RB4, INTCON.0 is set, BUT the interrupt enable bit is cleared on the same time. That's why it doesn't interrupt.

Now I have forced the enable bit to stay set, only when I run it then it gives me an adress missmatch error. So that isn't the solution... :)

Anyone with a clue what might reset INTCON.3?

1 Attachment(s)

Odd...

Okay, in debug mode all works fine now, but, when I compile and load the program without the debugger, then it goes bananas. What I suspect now, is that there is a signal in PortB what is resonating when I press the button. This will cause many interrupts, making the microcontroller think that I press the stop button right away.

That will explain why it skips the interrupt routine without the debugger on...

Before I order any parts to solve this, I want to know if I'm close or not. So is this a problem that might occure while making something like this?

Cheers,

William

Quote:

Originally Posted by WishMaster^

A colleague told me to make some own save location (pclhulp, whulp and sthulp). I'm not sure if this is okay...

I don't think I'd be listening to that guy too much.

If you are using a chip with more than 2K of program memory,PBP automatically inserts code to do the context saving. It uses the wsave, ssave and psave variables. Why? I don't know. But it does.

In the process of saving the context, it also changes the W and STATUS registers. So if you try to save and restore it with different variables, you're only saving the changed values. Then the real values never get restored.

This will send PBP to the Funny Farm. Or at least the person trying to figure it out.

So, lose the saving portion of the interrupt handler, then change the restore section to what's shown in the manual.

HTH,

Quote:

Originally Posted by Darrel Taylor

I don't think I'd be listening to that guy too much.

If you are using a chip with more than 2K of program memory,PBP automatically inserts code to do the context saving. It uses the wsave, ssave and psave variables. Why? I don't know. But it does.

In the process of saving the context, it also changes the W and STATUS registers. So if you try to save and restore it with different variables, you're only saving the changed values. Then the real values never get restored.

This will send PBP to the Funny Farm. Or at least the person trying to figure it out.

So, lose the saving portion of the interrupt handler, then change the restore section to what's shown in the manual.

HTH,

Allright! I already had my doubts about that! I changed it back right away and it works just as great! Thanks! :)

I fixed the problem with the "resonating signal". Turned out I used a wrong capacitor so the signal sticked in the forbidden area too long...
Back to newbie class for me I guess, haha.

Now comes the real challenge, 3 time measurements at the same time with 3 different start/stop buttons. All working on interrupts... Wish me luck! :D

Cheers,

William

1 Attachment(s)

Working code

For those who want to make a Stopwatch, here is my code for it. You will have to tune Timer0 for exact readouts since it is not perfect yet. By 30 seconds it will be 1,5 seconds off (28,5 sec)

It counts from 100 uS

Have fun building your stopwatch :)

Thanks to all who helped me to make the code as it is now!

Cheers,

William

P.S, I'll keep you all informed about the 3-stopwatch-at-the-same-time-based-on-interrupts-program ;)

Quote:

Originally Posted by WishMaster^

For those who want to make a Stopwatch, here is my code for it. You will have to tune Timer0 for exact readouts since it is not perfect yet. By 30 seconds it will be 1,5 seconds off (28,5 sec)
It counts from 100 uS
Have fun building your stopwatch :)
Thanks to all who helped me to make the code as it is now!
Cheers,
William
P.S, I'll keep you all informed about the 3-stopwatch-at-the-same-time-based-on-interrupts-program ;)

I almost hate to point this out to you since you've already got all this work into your project/code...but...
Do a search on 'Olympic Timer'...
You'll find a timer that Melanie did awhile back, and it's very accurate...well, at least as accuracte as your oscillator is.

Right! There's ...

Olympic Timer (Melanie)
http://www.picbasic.co.uk/forum/showthread.php?t=632
   Uses ON INTERRUPT<br>

Easy and Accurate Clocks without RTC IC (paul borgmeier)
http://www.picbasic.co.uk/forum/showthread.php?t=2129
   No Interrupts<br>

Elapsed Timer Demo (Darrel Taylor)
http://www.picbasic.co.uk/forum/showthread.php?t=190
   ASM Interrupts<br>

Elapsed Timer for Instant Interrupts (Darrel Taylor)
http://www.picbasic.co.uk/forum/showthread.php?p=17473
   Instant Interrupts<br>

Here's one based on Roman Black's routines (shahidali55)
http://www.picbasic.co.uk/forum/showthread.php?p=22173
   No Interrupts

And now there's...
Working code (Stopwatch) (WishMaster^)
http://www.picbasic.co.uk/forum/showthread.php?p=36939
   ASM Interrupts

Now all we need is ...
_ _ _ _ _ _ _ _ _ _ _ (skimask)
http://www.picbasic.co.uk/forum/show...?p=dontknowyet
   ???? Interrupts

Quote:

Originally Posted by Darrel Taylor

Right! There's ...
Now all we need is ...
_ _ _ _ _ _ _ _ _ _ _ (skimask)
http://www.picbasic.co.uk/forum/show...?p=dontknowyet
   ???? Interrupts

Jack of all trades, master of none. I know you've seen me say it before, I'm not doing anything that somebody else has already done...
Maybe someday I'll come up with something really neat and revolutionary to post...but I haven't come up with anything just yet...(that FFT routine adaptation I've got posted on my webpage for the PIC18Fxxxx is under an NDA, otherwise it would be here in a second).

Quote:

Originally Posted by skimask

I almost hate to point this out to you since you've already got all this work into your project/code...but...
Do a search on 'Olympic Timer'...
You'll find a timer that Melanie did awhile back, and it's very accurate...well, at least as accuracte as your oscillator is.

Yeah, I saw that one... But I learned much more about assembly and stuff with my own code then by simple copy/paste.

And if I finish the main project, the 3-timers-thing, then I will share the happiness too. Might be handy to clock the top3 formula 1 cars when you are at a race or something :P

Here it will be used for viscositymeasurements (http://en.wikipedia.org/wiki/Viscosity), where we can start a measurement at any time we want and not one per time (time = money and stuff ;) ).

And, most important reason of all, making your own code is so much more fun, seeing it grow and on the end, see it work! :D

Cheers,

William