Re: [avr-gcc-list] measuring uC supply voltage

[Joerg Wunsch]

JAMIE MORKEN <address@hidden> wrote:

> I am trying to figure out the best way to measure the 5V supply
> voltage for an atmega128.  I am using the 5V supply as the ADC
> reference voltage.

Why don't you just reverse the logic?  Keep Vcc as the reference
voltage, and use ADMUX == 0x1e to measure the 1.22 V bandgap
reference.  As your actual reference (Vcc) voltage varies, you'll get
a different ADC readout for the internal bandgap ref.  That way, you
could calculate that one back to the actual Vcc level.

-- 
J"org Wunsch                                           Unix support engineer
address@hidden        http://www.interface-systems.de/~j/