Re: Simple but wrong code

Todd thank you very much for your contribution.

I added this line to the bottom of the ISR:

PCIFR | = (1 << PCIF3);

and I have also added a 10 uF capacitor to remove any possibility of 
bouncing (... and seeing the signals to the oscilloscope are very clean 
and exactly as expected).

The behavior remained absolutely identical. :-(

I can not use a polling technique for reasons of timing, and even a 
software debouncing (negate the advantages of the ISR).

To me it remains unclear why exactly does two flashes on press and on 
release the other two flashes (Why not sometime a single 1 or 3?) for a 
total of 4 flashes instead of just one.

Thanks again

Domenico

Il 14/01/2014 18:02, Todd Batzler ha scritto:
> You're in that isr a long time.  The isr bit that got set that resulted in the vector to your isr probably gets cleared upon entry to the isr, but could get set again due to switch bounce.  Try clearing the ISR pending flag for that ISR before returning.
>
> Todd G. Batzler
> Sr Staff Engineer
> Technology Development
>
> Miller Electric Mfg. Co.  An ITW Company
> 1635 West Spencer St.
> P.O. Box 1079
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>
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On Behalf Of dfx
> Sent: Tuesday, January 14, 2014 10:54 AM
> To: [email protected]
> Subject: [avr-gcc-list] Simple but wrong code
>
> Please consider this code:
>
> #define KEY_PORT PORTD
> #define KEY_DDR DDRD
> #define KEY_FUNC_SEL PIND4 // --> first key (Port D pin 4) ....
> #define LED_PORT PORTB // Test led, to see action on keypress ....
>
> #define FUNC_SEL_KEY 0x10 // First function --> first key (Port D pin 4) ....
>
> int main() {
>     init();
>
>     while (1) {
>       // waits indefinitely for keypress
>     }
>     return (EXIT_SUCCESS); // Never reached }
>
> void init() {
>     cli();
>     LED_DDR |= (1 << DDB0); // Led out Port B pin 0
>
>     KEY_PORT |= (1 << PORTD4) ; // pull-up resistor
>     PCICR |= (1 << PCIE3); // Enable interrupts on PORTD (PCINT31:24)
>
>     PCMSK0 = 0X00; // Disable unnecessary
>     PCMSK1 = 0X00;
>     PCMSK2 = 0X00;
>     PCMSK3 |= (1 << PCINT28); // Enable  key
>     sei();
> }
>
> ISR(PCINT3_vect) { // FUNCTION KEY
>     uint8_t i;
>
>     i = PORTD;
>     if ((i & FUNC_SEL_KEY) > 0) { // Test a key
>       LED_PORT |= (1 << PORTB0);
>       _delay_ms(100);
>       LED_PORT &= ~(1 << PORTB0);
>       _delay_ms(300);
>     }
>     reti();
> }
>
>
> ISR(BADISR_vect) {
>     LED_PORT |= (1 << PORTB0);
>     _delay_ms(200);
>     LED_PORT &= ~(1 << PORTB0);
>     _delay_ms(200);
>     LED_PORT |= (1 << PORTB0);
>     _delay_ms(200);
>     LED_PORT &= ~(1 << PORTB0);
>     _delay_ms(200);
>     LED_PORT |= (1 << PORTB0);
>     _delay_ms(200);
>     LED_PORT &= ~(1 << PORTB0);
>     _delay_ms(200);
>     reti();
> }
>
> the button has a capacitor 1uF for debouncing (together with the pull-up from 10 kohm)
>
> The result is the following:
>
> when I press the button,  are generated two flashes (instead of one),
>    and when I release the button  are generated two more flashes.
>
> Similarly, If I comment out the routine (ISR PCINT3_vect),
>    the error routine (ISR BADISR_vect) generates double of the expected flashes.
>
> Can anyone help me to understand the problem?
>
> Thank you very much.
>
>
> --
> Domenico
>
>
>
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