Standalone Arduino (ATMega328) on a breadboard

Arduino Uno board is really amazing for prototyping, but you will soon need to build your own Arduino-like "board" based on an ATMega328 microcontroller, especially for projects where available space is limited and you can't fit an Uno with it's shields. The following Fritzing schema shows how to wire an ATMega328 (with Arduino bootloader installed) on a breadboard (click on schema for full-size image) :

Parts list

These are the components you'll need :

• 1 x Atmel ATMega328 with Arduino Optiboot bootloader : US$ 5.20
• 1 x 16 Mhz crystal (or 16 Mhz ceramic resonator) : US$ 0.95
• 2 x 22 pF ceramic capacitors (not needed if you use a ceramic resonator) : $US 0.25 each
• 1 x 100 nF (= 0.1 µF) capacitor : $US 0.25
• 1 x 10 kΩ resistor : $US 0.25
• 1 x pushbutton (Normally Open) : $US 0.35

All these components for no more than $US 7.50. We can still do better and reduce the bill by $US 1.20, flashing a bare ATMega328 ($US 4.30) and by $US 0.50 using a ceramic resonator so the two 22 pF caps are not needed, that is as low as $US 5.80 for an Arduino Uno clone !

Not mandatory but nice to have, an additional ~220 Ω resistor and a LED will be useful for testing purposes. If you do not have one yet, you'll also need a 5V USB to Serial converter (FTDI cable, $US 17.95 or breakout board, $US 14.95), that you can wire a shown on the schema :

• VCC to VCC (+5V)
• GND to GND
• RX to TX (pin 3)
• TX to RX (pin 2)
• DTR to Reset via a 100 nF (0.1 µF) capacitor

ATMega328 Arduino Uno pinout

You will probably be using Arduino's native functions to deal with I/O pins, so here is a table mapping ATMega328 pins and Arduino's :

(Schema from Sparkfun)