Friday, July 22, 2011

designing home-grown ATTiny84 development board part 2

Tonight I finally got by big shipment in from Digikey.  Good thing, because I don't know if I could've waited another weekend! After already designing everything on a piece of paper I had a pretty good idea on how I was going to lay it all out.

Here's a run down of what is all going on here.

How it works
I have power coming in through a barrel jack. It can be 5-18V.  Right now I'm using a 12V from an old router. The power (Vcc), then, is wired through a power switch and then into the 5V regulator's input.  From here it's going to the chip, an LED and the ISCP 6 pin header.  Into the XTAL1 and XTAL2 pins on the microcontroller I have a 20MHz oscillator. There's pull up resistor going to the ~reset pin on the microcontroller which is also tied to a button which when pressed brings the ~reset to ground (this I'd like to call a reset button).  An LED is wired in to indicate power on.  For when power isn't coming in through a DC inverter from the wall, I bought this for other types of power (batteries and such).

Design
My design idea was to keep this board as compact as possible. Why? Not really sure.  It's the first thing I've ever done with perf board, and it was a pretty ok experience.  The way I designed it, from what I can tell, wasn't very beginner-oriented.  There was a lot of soldering that was very close, and all of this makes many things like holding a component in the board upside down more difficult than they need to be.

Changes
Well there is one thing that probably isn't good.  As you'll be able to see, the ISCP 6 pin header is too close to the female headers for the microcontroller pins.  My plan is to shave the corner off of the female programmer plug until it fits.  I really hope this works; I'm not sure it's the best plan.  If this doesn't work I'll probably wrap 6 wires around the pins and solder in a new header. That's not too much work, but it's unfortunate it had to work out like that - it was so close!!

The bad
The programmer I ordered from adafruit didn't come in the mail today so I can't even program it after all that work! Well it's understandable because adafruit is out of NY, Digikey is in MN and I'm in WI.

Pictures










More will come when I get them uploaded!!

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