interrupt and sleep mode : how to make it work on attiny84 ?

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1

Hi,

I'm working on a project which will run on a attiny84. I'm testing it with an Arduino Uno.
I want to tell the chip to go to sleep mode (SLEEP_MODE_PWR_DOWN), then to wake up on an external interrupt (INT0).
It works like a charm on arduino uno... but not at all on attiny84. The chip just does not go to sleep and the interrupt is not caught.

do i need to add some libraries to make it work on attiny ?
do i use the right syntax for attachInterrupt ? (i tried attachInterrupt(INT0,wakeUpNow, LOW); : it just freeze the chip.)

Here is the code :

#include <avr/sleep.h>

void sleepNow()
{
  set_sleep_mode(SLEEP_MODE_PWR_DOWN);
  sleep_enable();
  attachInterrupt(0,wakeUpNow, LOW); // interrupt : INT0 (pin 0)
  sleep_mode();  // go to sleep...
  sleep_disable();  // wake up !
  detachInterrupt(0);
}

thanks for your help !
Fab

2 
  attachInterrupt(0,wakeUpNow, LOW); // interrupt : INT0 (pin 0)

What pin on the chip is that? I can't find the list of Arduino -> hardware pin mappings for the 84.

3

it should be pin 0 ?
[url=ATtiny84 Pin Layout for the arduino-tiny core | arduino-tiny… | Flickr]ATtiny84 Pin Layout for the arduino-tiny core | arduino-tiny… | Flickr
http://www.atmel.com/Images/doc8006.pdf

4

The Atmega84 has 14 pins, numbered 1 to 14. There is no pin 0. See the datasheet you linked.

Pin 1 is VCC and pin 14 is Gnd.

I'm trying to establish which, of those 14 pins, you are connecting the thing that is interrupting it to.

5

Hi guys

Arduino IDE D0 references ATtiny84 physical leg 2 which is also XTAL1 if you're using a crystal, and PB0.

The datasheet states this uC family has "Internal and External Interrupt Sources: Pin Change Interrupt on 12 Pins" which is promising, but potentially you've connected to the wrong leg?

Cheers ! Geoff

6

I make it physical pin 5, which is why I am asking which pin he actually is using.

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7

[quote author=Nick Gammon link=topic=134698.msg1013219#msg1013219 date=1354139195]
I make it physical pin 5, which is why I am asking which pin he actually is using.
[/quote]Of course - the first param is the interrupt number not the pin number. Apologies.

8

Damned ! i was confused with "PCINT0" so i wired the switch on physical pin 13. I did not tried pin 5.
Too bad, physical pin 5 is also one of the 4 pwm output of the at84 and i need all of them !
The datasheet states "external interrupt on 12 pin" (from pin 2 to pin 13 / pcint0 to pcint11), but i have no clue on how to make it work in an arduino sketch. Is there someting like attachInterrupt() for external interrupts ?

thanks all for your advices !
Fab

9

I'm not sure exactly about the Attiny84, but pin change interrupts are easy enough:

There is a pin change interrupt library, not sure if it supports that processor.

10

Gammon Forum : Electronics : Microprocessors : Interrupts

there is a lot of very valuable information there !

Thank you Nick !

11

i agree. and thanks for your paper on microprocessors: power saving techniques.