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[on:]

I am still trying to figure this out and I know some out there has asked this same question with different words, but can I build a prototype on my uno r3 and then build for real off just the chip and (i assume we need) a crystal?

I found this

http://www.hobbytronics.co.uk/image/data/tutorial/arduino-hardcore/atmega328-arduino-pinout.jpg

and it looks like the start to my question but i want to know things like:
can i still have a reset button?
What are pins 20 21 & 22 (ARef)?
I have never seen a chip with power not on the corners but i am to believe that +5v is on pin 7 and ground is 8?
What is the voltage tolerance?
Should i even ask what SPI (pins 17,18&19)& I²C(27&28) is?

thanks for the support in advance!

[Reply #1 on:]

I did that here:

http://www.gammon.com.au/forum/?id=11637

You don't need a crystal if you don't mind running at 8 MHz.

You can have a reset button if you want. If you want SPI (for ICSP programming) you can break out those pins.

Diagram:

[Reply #2 on:]

That picture is a mapping between the physical pins of an Atmega328p in DIL package and Arduino Uno pins.

Read first, a bit, the Atmega328 datasheet. It will clarify many of your questions.

As regarding power pins, there are dozens of chips with VCC and GND pins in the middle of pin rows.  

[Reply #3 on:]

There are two fairly straightforward paths:

1. Do what you said, that is, take the chip out of the Arduino and put it in your circuit. In this case you will need a crystal and caps, or alternatively a 3-terminal ceramic resonator, because the fuses in the atmega328p you take out of the Arduino are set for an external crystal/resonator. You will need to buy a replacement atmega328p chip with bootloader already installed to get your Arduino working again.

2. Buy a blank atmega328p chip for your design, include the 6-pin ICSP header in your design, turn your Arduino temporarily into an ICSP and use it to program the chip in your design. In this case, you can decide whether to use a crystal/resonator or not. See http://miscsolutions.wordpress.com/2011/08/09/prototyping-small-embedded-projects-with-arduino/ for more about this approach.

[Reply #4 on:]

I did that here:

http://www.gammon.com.au/forum/?id=11637

You don't need a crystal if you don't mind running at 8 MHz.

You can have a reset button if you want. If you want SPI (for ICSP programming) you can break out those pins.

Diagram:

Hi
I would like to ask you about the capacitors near the crystal. Which are their description ?

[Reply #5 on:]

I would like to ask you about the capacitors near the crystal. Which are their description ?

Both are 18pF or 22pF ceramic. Alternatively, use a 3-terminal ceramic resonator instead of a crystal (like the Arduino Uno does), which gives you a slightly less accurate frequency (usually +/- 0.5%) but has the capacitors built-in.

[Reply #6 on:]

I would like to ask you about the capacitors near the crystal. Which are their description ?

Both are 18pF or 22pF ceramic. Alternatively, use a 3-terminal ceramic resonator instead of a crystal (like the Arduino Uno does), which gives you a slightly less accurate frequency (usually +/- 0.5%) but has the capacitors built-in.

Useful Info !
Thank you very much for your immediate response !