16f688 interrupt

[RHS_electronics]

We are trying to set up a button interrupt on port Ra.5 on the 16f688 chip to light a led, this is the first time that we have worked with the innterrupt command, any suggestions? Will post the program that we have so far if necessary.

[RHS_electronics]

Trisa = 32
Trisc = 0

ioca=%10000000
a Var porta
c var portc

t1 var word
t1=200
start:

on interrupt goto buttonpressed
INTCON = %10000000 
one:
    gosub left:
    

    goto one:

buttonpressed:
    gosub All_on:
 
    
    goto buttonpressed:                      
resume



''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
'SUBROUTINES
left:
a=4:c=36
pause t1
a=0: c=0
pause t1
return

all_on:
a=7:c=63
pause t1
return

Here is the code, If i will help at all.

[Darrel Taylor]

Got a few problems there ...

For Interrupt on change with RA5, you need to set bit 5 of the IOCA register. You have bit 7 set.

ioca=%00100000

Then the PortA change interrupt needs to be enabled (RAIE)...

INTCON = %10001000

In the interrupt handler (buttonpressed), you MUST read PORTA to end the mismatch condition, and clear the interrupt flag before exiting the handler. And it must exit the handler. You have a continuous loop in there, remove the goto.

buttonpressed:
    gosub All_on:
    dummy = PORTA  ; clear mismatch condition
    INTCON.0 = 0   ; reset interrupt flag
resume

Keep in mind that you will get an interrupt on both the Press and Release of the button. You will eventually need to change the interrupt handler to determine which Edge occurred.

RA5 is also a main oscillator pin. I assume you are using the internal oscillator .. just checking.

You should turn off the Analog functions when using Digital signals.

ANSEL = 0

And disable the comparators.

CMCON0 = 7

[RHS_electronics]

dummy = PORTA

What do you mean by this?



Also we are trying to make the button, when pressesd, toggle between two subroutines, Exe: one press is the first one, then when you press it again it will go to the next program.

ps: yes we are using the internal oscillator

[Darrel Taylor]

dummy=PORTA

What do you mean by this?

You'll need to have a BYTE variable

dummy  VAR BYTE

At this point the variable isn't used for anything.
But by simply reading PORTA, it resets the Latches used to detect the change on the Port.

Without clearing the "Mismatch" condition, there's no way to reset the interrupt flag.
So as soon as you RESUME from the interrupt handler, it would jump right back into the interrupt again.
<br>

[RHS_electronics]

Trisa = 32
Trisc = 0


a Var porta:c var portc
x var word:t1 var word
dummy var byte

x=0
t1=200

ANSEL = 0
ioca=%00100000
CMCON0 = 7
start:

on interrupt goto buttonpressed
INTCON = %10001000 
one:
   
    gosub left
     

    goto one

buttonpressed:
    gosub All_on
    dummy=porta  ; clear mismatch condition
    INTCON.0 = 0   ; reset interrupt flag

   
resume                     




''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
'SUBROUTINES
left:
a=4:c=36
pause t1
a=0: c=0
pause t1
return

all_on:
a=7:c=63
pause t1
return

This is the code we have now and it still isn't working, the only thing it is doing is stopping the program where it is, What is wrong?