AVR-Chat

You can also set the BOD to different voltages.  Are you able to run the part at a high enough voltage to allow enough time to run some cleanup stuff in the interrupt before the voltage goes all the way down?  Maybe just increasing the size of some of your capacitors would give you the extra few milliseconds to do something worthwhile.  That wouldn't help your existing hardware but it would let you add the feature without a board spin.

----- Original Message -----
From: "bayramdavies" <Yahoo37849@ecrostech.com>
To: AVR-Chat@yahoogroups.com
Sent: Friday, January 25, 2013 10:23:42 AM
Subject: [AVR-Chat] Re: Brown-Out detection

--- In AVR-Chat@yahoogroups.com, "Chuck Hackett"  wrote:

> How does one detect that VCC is dropping
> so that one can do cleanup activities ...

Ideally, you would detect loss of power *before* VCC starts to fall, for example the failure of the AC input at the main power supply.

Anyway, you've said that you have to use existing hardware.  But, you've told us nothing about that hardware.  What is the nominal supply voltage?  What is the lowest brownout voltage that you can set?  How fast does the supply fall when power is removed?  How is the A-to-D wired up.

If there is enough time between the supply starting to fall and reaching the brownout level, you may be able to configure the A-to-D to measure the 1.1 volt band-gap using AVCC as a reference.  If this rises sharply, then AVCC has started to fall.

On a different subject, I don't suppose you could use a bunch of ATmega1284P-AU (TQFP-44)?  I have 25 I bought for a project which then disappeared and I would let them go for $100 the lot.

Graham.




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