XTAL capacitors on standalone ATMEGA328

Hi all,

I just have a question about a small project I'm working on, which involves taking a programmed ATMEGA328 chip out of my Uno, and using it as a standalone unit. It basically runs an LED dot matrix display, but it seems that it resets part way through the program and starts over again. Now I've read that the capacity of capacitors at the crystal is required to be 22pf, but I'm currently using 33pf since that's what I've got on hand and none of my local shops carry 22pf caps. Is it possible that this could cause the behaviour I'm seeing? If so, how and why?

Just a fanatical newbie on the quest for knowledge

Thanks in advance,

Matt

Oh, and on a side note I'm just downloading Fritzing and will work on a breadboard layout and post it if necessary.

No that will not cause a reset.

What will cause one is lack of decoupling capacitors on the chip's power pins. Some crappy stand alone circuits do not have any at all.

I have 10uF caps on the 7805 regulator I'm using. I'll follow up with a layout as soon as I'm finished it (just working on it right now).

c0utz:
I have 10uF caps on the 7805 regulator I'm using. I'll follow up with a layout as soon as I'm finished it (just working on it right now).

Not good enough.
You need a 0.1uF ceramic cap on the two powe pins and one on the Aref pin. You also need caps either side of the regulator.

There's a layout of what I had.

So not only no ceramic decoupling caps but also no current limiting resistors on the LEDs - double bad.

There are resistors on the LEDs, It's a small PCB with with a few caps/resistors and a max7219. I just didn't show them because I was trying to keep the layout simple as this is the first time I'm using Fritzing. Sorry for the confusion. As for the caps I'm missing, you're saying I should have them on pins 20, 21, and 22?

There is little point in posting something with errors in it. You only distract from your real problem.
Pin 7 I believe is a power input, so a cap from there to ground which is pin 8. Then a cap between the analogue power input and ground and the Aref and ground ( can't remember the exact pin numbers but arround what you said )