On Interrupt question

[sougata]

Hi,

It seems at a quick glance that you are using the interrupt on change feature on portb. This means you trigger an interrupt on every change on portb<4:7> . In plain english on every edge , a press or release of the button. So the program is jumping into the routine. Without rewiring your circuit you can disable the interrupt altogether in the interrupt routine and then clear flags and set the interrupt in the main loop.

BTW its 22:05 here and time to go home so signing off now.

Regards

Sougata

[peu]

The interrupt is triggered as soon the pic starts, without even pressing a single time any button.


I set the OPTION_REG as follows

bit7 = 1 PORTB pull-ups are disabled
bit6 = 1 Interrupt on rising edge of RB0/INT pin
bit5 = 0 Internal instruction cycle clock (CLKOUT)
bit4 = 1 Increment on high-to-low transition on RA4/T0CKI pin
bit3 = 0 Prescaler is assigned to the Timer0 module
bit2 = 0 Prescaler Rate Select bits
bit1 = 0
bit0 = 1 TMR0 Rate 1:4 WDT Rate 1:2

I can rewire the schematic at will, so if you have a solution this way, please let me know.


Thanks!

[sougata]

Hi,

Try using the portb.0 interrupt pin. Clear the interrupt flags (other than Global int.7) just before the resume and your circuit should work. Try using some sort of debounce circuitry as well. Good Luck. BTW your PIC has a hardware PWM. After the experiment put it to good use.

Regards

Sougata

[peu]

Hi again Sougata,

I need 3 PWM thats why I use the soft version. And regarding the interrupts I need 2 buttons, thats why I choosed the port change instead of the single PortB.0 method.

Any idea on how to do that?

Thanks again!

[Archilochus]

Hi Pablo,
As sougata mentioned, you'll have problems with switch bounce and button press duration causing repeated interrupt flag resets.

Since your code is not 'seeing' an interrupt until after the PWM statements are finished, why not just test the state of the interrupt flag in the pauses in between your PWM loops?

As far as interrupting on power up without a button press, you might try a bit a a pause at the start of the program, then clear the interrupt flags.

Arch

EDIT - ooh... that won't work 'cause it won't sort out the different buttons - darn!

[sougata]

Hi,

On a closer look at your prog I found that you have timer0 to use external clock via RA4. Possibily you did this because there is no timer0 enable disable bit. You wanted your timer not to work. But you have kept the input floating. Spurious counting is going on. Also you have turned on the timer0 interrupt bit in your intcon settings. So a timer0 overflow would trigger the interrupt.

So my suggestions :

1. Disable the T0IE bit

Regards

Sougata

[peu]

Thanks Sougata, I changed that bit and now it works as expected.

A single bit keep me puzzled half week, you gotta love pics...

Here is the working example, so others can learn too:

@ device pic16F628A, intrc_osc_noclkout, wdt_on, mclr_off, protect_off
DEFINE OSC 4

trisb   =%11111111
trisa   =%00000000
cmcon   =%00000111  'Comparators Off
vrcon   =%00000000
intcon  =%10001000'interrupts enable // was  %10101000  
'OPTION_REG =%11010001 

but1    var PORTB.4
but2    var PORTB.5
ledwork var PORTA.0
led1    var PORTA.1
led2    var PORTA.2
led3    var PORTA.3
rs      var PORTb.2


conta   var byte

porta=0
portb=0

on interrupt goto interrupcion

SerOut rs,2,[" ",10,13]
SerOut rs,2,["Begin",10,13]


LOOP:

SerOut rs,2,["Loop",10,13]

for conta=0 to 255 step 16  'working led rise routine
    pwm ledwork, conta, 10  
next conta
high ledwork

for conta =0 to 10
    pause 10
next conta

low led1   'set button status leds off
low led2
low led3


goto loop

end
disable 
interrupcion:
SerOut rs,2,["Interrupt",10,13]
    intcon.0=0
    intcon.1=0
    intcon.2=0
        if but1=1 then
             but1=0
            high led1
            SerOut rs,2,["Set",10,13]

        endif
        if but2=1 then
             but2=0
           high led2
           SerOut rs,2,["Mode",10,13]
        endif
high led3       

    resume
enable

I commented out the OPTION_REG because the program worked ok with and without it. Of course the serouts can be removed, I use them to know where the program is.

Thanks to all for the help provided


Pablo