Interrupt mystery - need some guru help

[xnihilo]

is it because pic sets all ports to input pins upon powerup?

[BobP]

Hi xnihilo,

skimask has pinpointed the passage in the datasheet that clearly tells you what you need to do before enabling the interrupt and after servicing the interrupt. I appreciate that English is probably not your first language but re-examine the paragraph and what it tells you is required before enabling the interrupt?

Regards,
Bob

[xnihilo]

Please, no more riddles.

I beleive the portA has to be read prior to enabling interrupts.


Are these steps order right?

- enable weak pullups with OPTION_REG = %01111111 (even if I DON'T know what should be the settings for bits 0 to 6, which seem not useful for me)
- enable WPU for desired ports, for me it should be: 010111 (no WPU for RA3 which is used as an input port) (no WPU for RA5 which is used with default 0V and is activated when 5V gets to this pin)
- TRISA = %101111 because all porta pins has to be input except for pin RA4 which is used for R/S bit for an LCD pannel
- TRISC = %000000 (all output)
- PORTA.5 = 0 (I set specificaly RA5 to 0 because I want it to be LOW at the start, all other porta pins will be brought high automatically by WPU)
- PORTC = %000000 (I set all portC pins low)
- I initialize all my variables
- I put some stuff here like display on LCD
- IOCA = %101111 because I enable PORTA change interrupt for all porta pins except for the pin used for LCD R/S bit
- INTCON = %10001000 (I enable interrupts: GIE and portachange)
- ON INTERRUPT GOTO myroutine

Is that correct?

[skimask]

Please, no more riddles.

There's only one riddle...why haven't you read the section I specified earlier?
It's right there in the datasheet...Section 4.2.3, 2nd paragraph.

[xnihilo]

There's only one riddle...why haven't you read the section I specified earlier?
It's right there in the datasheet...Section 4.2.3, 2nd paragraph.

I did.
Never mind, I will ask in another forum.

I think the problem comes from the fact that my RA3 is linked to nothing. I will connect it to 5V via a 10K resistor.

[skimask]

Never mind, I will ask in another forum.
I think the problem comes from the fact that my RA3 is linked to nothing. I will connect it to 5V via a 10K resistor.

Hey, I'm just trying to help you learn how to read a datasheet...or at least read between the lines in a datasheet. Some of the information is a bit subtle.
And yes, it's a distinct possibility that a floating input could be triggering something it shouldn't.

[mbruno]

Re-Read the replys the Clue to solve your mystery is "I.O.C."...
hopes this helps just a little