The Bare Bones...

Description:
A 50mm x 50mm printed circuit board designed to be a bare-bones Arduino board based around the Atmel ATMega 328P-PU.  On the left side are all components required to power and regulate the chip.  On the right side is a small prototyping area with Ground and Vcc rails.  Pins for accommodating a TFT display are along the top.

Details:
Perhaps it's a rite of passage, but everyone who fiddles with Arduinos eventually makes a bare-bones board (BBB), something that makes use of the input/output pins and capacity of the ATMega328 chip without the additional overhead that comes on an Arduino Uno board.  For multiple tinkering sessions with a breadboard, the Uno can't be beat... but after that's done you don't want to give up your Uno in the final application.  Plus, going this route lets you optimize power requirements a bit better.

So this is my BBB... I'll call it first-generation because I laid it out before getting my awesome new soldering station and learning how to lay down surface-mounted components.  It measures about 5cm square.  As before, I designed it using Fritzing and had it fabricated through SeeedStudio, so they cost about $2 each after shipping.

Features (going clockwise around the board):

• Upper-left corner: +/- for direct battery connection if you want to hardwire a AA battery holder to this
• Upper side middle: eleven holes to directly align with a 1.44" color TFT display (Adafruit #2088), but really all I've done is break out the usual SPI pins to make them accessible.  From left to right, the pins are: Blank, P4, P8, P9, P10, P11, P12, P13, Ground, Blank, Vcc.
• A 6x14 prototype board area, with ground and Vcc rails on each side
• Bottom center: three pins for a DS18B20 digital temp sensor and 4.7k resistor.  The signal from the temp sensor goes to P7 on the chip.
• Left-side lower: 5 pins for a micro-USB breakout board (Adafruit #1833)
• Left-side middle: space for an Infrared receiver diode in case you ever wanted this for a remote-control application
• The open holes on the remaining pins are, well, open -- you just run jumpers over to the proto area.