Re: [avr-gcc-list] Simple but wrong code

[Mark Litwack]

I would try connecting a pulse generator to the keypad input and send
it a single pulse.  At least this will help narrow it down to either a
SW or HW issue.

And unless you can always distinguish expected ISR blinking from
BADISR blinking, I would not have the BADISR blink.  It could be
getting called unexpectedly.

I thought Todd's suggestion would have nailed it for sure...  And
David is right you don't need the reti(); it is only used when writing
a naked ISR.  Who knows what evil is lurking in the stack on a
premature return.

-mark



On Tue, 14 Jan 2014 18:37:54 +0100
dfx <address@hidden> wrote:
> 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
> > Appleton, WI  54912-1079
> > 920-735-4230 Office
> > 920-735-4488 Fax
> > address@hidden
> > www.millerwelds.com
> > Please consider the environment before printing this email.
> >
> > -----Original Message-----
> > From: address@hidden [mailto:address@hidden On Behalf Of dfx
> > Sent: Tuesday, January 14, 2014 10:54 AM
> > To: address@hidden
> > 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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