AVR-Chat

On Sun, Apr 24, 2005 at 03:22:00AM -0000, arhodes19044 wrote:

> Yes it is the Mavcric-IIb!  I am glad the cap is already there.  I
> foud that I got decent readings once I fixed my code and set the ACR
> to use the AVCC instead of the "default" AREF.
> 
> One other question:  in one of the little write-ups here on ADC, it
> said that "AVCC should be connected to VCC whenever PORTA is used a
> output.  This is because PORTA is always sourced by AVCC."  I think
> this write-up was specifically dealing with the 8535, so I do not know
> how that info applies to the 128.

In this case of the ATmega128, that would be PORTF instead of PORTA,
since PORTF is the A/D port on the Mega128.

> I do not have AREF connected to anything and PORTA is working fine as
> output and input for my keypad scanning code. 
> 
> Is this true, and do I need to do anything special about it?

Yes, it's true (for PORTF), but you don't need to do anything - your
MAVRIC-IIB connects AVCC to VCC though a 10 uH inductor as specified
in the datasheet.  You are good to go!

-Brian
-- 
Brian Dean
BDMICRO - ATmega128 Based MAVRIC Controllers
http://www.bdmicro.com/