Magic Blue Demons and Testing a SMD ATmega in a breadboard

I apologize if this is getting too technical too quickly; but it’s what I’ve got for you (and, if you’ve managed to find this post it means you probably need it). I promise it’s a quickie.

Recently I acquired one of these awesome things:

It allows you to temporarily use a tiny square 44-pin surface mount microchip (qfp ATmega32U4 in my case) in use it in a breadboard to make sure you have everything like the multiple Vcc’s properly decoupled, etc. Also, I mean, just look at that:


Isn’t it just cool!? (It also makes a pretty satisfying *click* 😀)

But, I digress. Full of excitement, I wired up a simple regulated power and ISP circuit – nothing can go wrong! – plug in the 12V source and *POOF*

The magic blue demons got out. 😦

AS IT TURNS OUT, my assumption that “pin 1” marked on board would correspond with “pin 1” on the chip was absolutely ludicrous.
After googling around for a while, I couldn’t come up with a datasheet that showed the proper pin-mapping; so, I broke out the old multimeter continuity probe and made one!

1020160051As it turns out, in the aligned orientation, “pin 1” on the chip corresponds to the much more sensical “pin 7” and “pin 1” on the package (the pin on the top left corner) corresponds to a pin on the middle of an edge on the chip (“pin 39”) -exactly where no manufacturers begin their numbering scheme. Brilliant, I say!

Hopefully this was helpful to you if you, like me, were looking around for a drawing of how the pin map for this test-socket actually worked. If not, maybe you’ve learned something to lookout for in the future. And if nothing else, maybe I’ve helped you proscrastinate successfully 😀