Reading the pin charts...

So this is a stupid question but how the hell do you correspond the pins in the charts. IE physically where is pins 10 (vcc) and 11(gnd) in the table below.

http://arduino.cc/en/Hacking/PinMapping2560

If you are looking at the chip from the top, just like in that diagram, you count pins counter-clockwise, just like in that diagram.

Of course for other package types the pins are in other places. Read the datasheet to figure out where.

This picture might be better quality. Top left hand corner is the index mark, pins number from 1 down the left side and continue counterclockwise till back to the index mark for pin 100.

http://www.siphec.com/microcontroller/ATmega1280-16AU%20ATmega2560-16AU.gif

What about tracing the chip pins to a header?

mginster: What about tracing the chip pins to a header?

Well one would then turn to a full schematic of a board, like the arduino mega/2560:

http://arduino.cc/en/uploads/Main/arduino-mega2560_R3-schematic.pdf

Or if your just conserned about the I/O pins to header pins, a simple 'cheat sheet' sometimes is all one needs: https://spreadsheets.google.com/pub?key=rtHw_R6eVL140KS9_G8GPkA&gid=0

Lefty

mginster: What about tracing the chip pins to a header?

For that you look at the red labels,