Let's Make Robots!

How hard would it be to build an Arduino?

I recently assembled the Really Bare Bones Board, pictured below.  It's an Arduino clone in a smaller and more affordable package.

RBBBrevB_front_800.jpg

The board is $12, which is a great deal.  But I want to lower my costs as much as possible.  During a 3-hour car trip today my mind was racing with ideas for potential robots, and I began realizing that for the projects I want to do I'm going to need multiple embedded microcontrollers.  What's more, each microcontroller board will need different appendages ... some with their own voltage regulation, others with motor controllers, some won't need analog input, and some will need LED's while others won't.  I like the idea of having each board with its own specific functions and abilities, rather than wasting money on an all-around package with some things I don't need and lacking something I might need.

Anyway ... the point is that it might make more sense for me to buy ATMega168's with the Arduino bootlegger and make my own microcontrollers.  Problem is ... I'm not entirely sure how to do that ... so maybe you guys can help me out? 

Ok so here's what I know I need: The ATMega168 needs a steady supply of 5 volts.  That's easy enough to pull off with a voltage regulator and a couple of capacitors. Next up is the resonator ... which I have a fairly good understanding of.  I know what pins to connect to, anyway, which I guess is all that matters.  Next up is a test LED, which of course is super easy.  And lastly the reset button, which I'm sure I can figure out.

Other than that, though, I don't know what the microcontroller needs to do its thing.  Looking at the RBBB, I don't know what all that stuff does.  What are the two capacitors for, for example?  There are two 47uF capacitors and I don't know what they do.  Does it allow for analog input via a resistor-capacitor circuit?  What about that diode there?  Is that for blowback voltage?  How about those resistors?  And lastly ... I'm very embarrassed to say I don't even know what the blue thingies are.  I'm assuming they're capacitors, but I could be wrong.

Thanks for helping out a beginner!  Sorry for the big blocks of text ... there's just so much I still don't know!!

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I ran across this ...

http://blog.makezine.com/archive/2007/07/barebones_arduino_on_a_br.html

So ... this Arduino has no capacitors.  If it can function without them, then what the heck are they for? 

Also, this is the RBBB schematic.  It kinda ... sorta ... helped me.  Well really it just confused me further.

http://moderndevice.com/Images/RBBB_revB_800px.gif 

The Arduino has small (22pf) capacitors near the crystal, which are required to guarantee that the oscillator starts up.  But if you're using a ceramic resonator, as shown in the photo, that device includes the capacitors so that you don't need to add them.  But, a ceramic resonator is not as accurate a frequency source as a crystal, which may or may not matter according to your application.  Resonators are also a little bit cheaper than crystals.

There are also some capacitors for decoupling (not quite the same thing as smoothing), connected from Vcc to Ground close to the chip.  The circuit shown in the photo omits these capacitors, which is a bad idea.  The circuit will appear to work, at least at first, but may be subject to random crashes.  The thing is, when a microcontroller crashes, how do you know whether your program had a bug or your hardware had a glitch?  It's best to include the decoupling capacitors and make a reliable controller for your robot.