SparkFun Forums 

Where electronics enthusiasts find answers.

Discussions on the software and hardware for Atmel's STK standard.
By aknickolai
So I've always put small 100nF caps on AVCC and AREF when I need to do analog to digital conversions on my atmel chips. Everything worked, but I just got an LCD working and I'm getting a ~15% error between what my meter and the A2D are claiming the voltage is. If I remove the cap on either AVCC or AREF (ie hardware the connection) the error goes away.

So, should I only be putting a cap on AREF and not AVCC? I've messed a ton with the code and trouble shooting, I'm sure it is a wiring issue related to the caps as removing them eliminates the error. Of course, it also eliminates any filtering as well, I'd like to keep that.
User avatar
By Ross Robotics
Yes, it is standard to put a 100nF cap in series with AREF.
You do not have the required permissions to view the files attached to this post.
By aknickolai
AREF makes since for sure. I guess I don't need one on AVCC, since eliminating that cap gets rid of my A2d error and I would keep the filtering on AREF. Thanks!
User avatar
By Ross Robotics
Correct, no need for a series cap on AVCC, just put it to your + supply. Just make sure you have some decoupling caps.
By AVRexpert
HEllo thanks for your question !
In order to use internal ADC you must give the reference voltage to the microcontroller . Connect your AVCC to reference voltage(5 volt generally ) and AREF pin to Ground . So that internal ADC of microcontroller take suitable reference . I have made a nice tutorial for you related to how to use ADC of microcontroller in Atmega32 microcontroller please visit this reference link [url][/url]
Thank you :clap: :dance: :clap: :dance:
By jremington
and AREF pin to Ground
Ignore this extremely bad advice, as the ADC will cease to function and the internal circuitry may be destroyed.

The ADC can be affected by noise in the power supply. If using Vcc as the reference, it is common to decouple Vcc and Vcc with a 10 uH inductor as well as capacitors.

See "noise cancelling techniques", section 24.6 and Figure 24.9 of the ATmega328 data sheet
long long title how many chars? lets see 123 ok more? yes 60

We have created lots of YouTube videos just so you can achieve [...]

Another post test yes yes yes or no, maybe ni? :-/

The best flat phpBB theme around. Period. Fine craftmanship and [...]

Do you need a super MOD? Well here it is. chew on this

All you need is right here. Content tag, SEO, listing, Pizza and spaghetti [...]

Lasagna on me this time ok? I got plenty of cash

this should be fantastic. but what about links,images, bbcodes etc etc? [...]