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mdown
Joined: 03 Feb 2006
Posts: 62
Location: Dallas, Texas
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Posted: 11 October 2007, 15:22 PM Post subject: External wake from CPUSleep() |
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The ATMEGA644 Docs hint at the possibilty to wake the cpu from powersave via I2C. Have any of you done this? What I2C device did you use? I am trying to find an I2C RTC device were we could set an alarm for say 30 min or longer and after that period of time it wakes the CPU.
-Mike |
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dkinzer
Site Admin
Joined: 03 Sep 2005
Posts: 2593
Location: Portland, OR
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Posted: 11 October 2007, 15:45 PM Post subject: Re: External wake from CPUSleep() |
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| mdown wrote: | | The ATMEGA644 Docs hint at the possibilty to wake the cpu from powersave via I2C. |
It is true that an I2C interrupt can wake up an AVR from a power save mode. For this to work, the I2C interface needs to be configured as a slave (which it isn't in the ZX) and the I2C interrupt needs to be enabled (which it isn't in the ZX).
The only wake up sources that are available on the ZX are: external reset, watchdog reset, brown-out reset, external interrupt (INT0-2 or pin change), Timer2 compare or overflow, and (in some sleep modes) ADC conversion complete.
Last edited by dkinzer on 12 October 2007, 1:25 AM; edited 1 time in total |
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stevech
Joined: 23 Feb 2006
Posts: 688
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Posted: 11 October 2007, 19:32 PM Post subject: |
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| some of the RTC chips have an alarm pin- goes true when the alarm goes on. And some have a low frequency square-wave output. Either could be connected to the AVR chip's external interrupt (INT0..2) pin, I'd think. |
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