External Interrupt on the ATtiny2313

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I was going to make simple robot that bumps into walls and then turns. I thought I could use a if statement but then I realized that I would need an interrupt. My problem is that I need the motor spinning until my snap action switches are trigged then turn accordingly in that direction but I don't know how to use external interrupts. Can someone tell me how to use external interrupts?

Thank in advance
Magnus,

Life Is Like A Bucket Of Chicken.

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Google search http://www.google.com/search?q=a...

First two hits are useful.

--Mike

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Be careful when using a mechanical switch to trigger an interrupt. Switch bounce is the key word here (if you're not familiar with the phenomenon, a search for "switch bounce" or "switch debounce", either here on Freaks or with Google should provide tons of hits). Basicly, when the robot bumps into the wall and the switch is activated, you won't have a clean transition from 1 to 0 (or the other way round), but rather a series of spikes; each of them able to trigger a new interrupt. Same thing happens when the robot reverses and the switch goes back - expect a series of spikes and multiple interrupts.

One way to deal with this situation is to temporarily disable the switch interrupt until "things have settled", ie. until the robot has backed a few millimeters and the switch is back in the normal position. At this point, clear the interrupt flag before re-enabling the interrupt. Otherwise, an interrupt request will probably be pending, and new interrupt will fire immediately when enabled.

There are lots of useful threads about interrupts, ig. this one: https://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&t=55347

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I would love to have those problems, but I haven't even got the interrupt to trigger. The code does compile and the while loop work but thats it. Heres my code my using the attiny2313 MCU and the USBtinyISP programer.

#include 
#include 
#include 


int main (void) 
{
	int i;
	
	DDRB = 0b00001111;
	DDRD = 0b00000000;
	
	PCMSK |= (1<<PIND2);
	
	MCUCR = (1<<ISC01) | (1<<ISC00);
	
	GIMSK  |= (1<<INT0);
	
	for (i = 0;i < 100;i++)
	{
		PORTB = 0b00001111;
		_delay_ms(1000);
		PORTB = 0b00000000;
		_delay_ms(1000);
	}
}

ISR(INT0_vect)
{ 
	int i;
	
    for (i = 0;i < 5;i++)
	{
		PORTB = 0b00000110;
		_delay_ms(1000);
		PORTB = 0b00000000;
		_delay_ms(1000);
	}
	
}

Life Is Like A Bucket Of Chicken.

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For an interrupt to fire, global interrupts must be enabled. You have defined the interrupt source, but have failed to enable interrupts globally. Try to include:

sei();

before entering the main loop. This command basicly sets the I bit in the status register.

When programming "the real thing" try to keep the ISR as short as possible; avoid long delays and such - when in the ISR nothing else gets done. Also, normally the main loop never terminates... But try to include the sei() first and see if the interrupt fires.

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Keep in mind also that the _delay_ms(1000) only works on the latest (20071221) release of WinAVR. Previous releases only permitted a much shorter delay. But, as mentioned, you want to exit your ISR as soon as possible.

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Finely It Work!!!, I've was scerwing around with the interrupts for a month trying to get it to work. Thanks everybody. :D :D :D

Life Is Like A Bucket Of Chicken.