Archive for April, 2010


Xmega chip and adapter pin diagrams


In designing a board, it used to be that you’d first connect up your various peripherals to the microcontroller at the appropriate ports, then figure out how to make the routing happen.  However, with the plethora of peripherals on the Xmega chips, you can arbitrarily move msot of your components wherever you want.  Need a serial port?  You’ve got anywhere from 5 to 8 depending on the chip, and they’re all perfectly interchangeable.  As such, I’ve taken to first deciding roughly where I want the various components on my board, then figuring out which of them connect where on the microcontroller.

However, the datasheets themselves aren’t entirely useful in this regard.  At the front of the manual you have the pinout that shows the shape of the chip and where the various ports are, and all the way at the end of the manual you have a series of tables that describe the alternate functions (i.e. peripherals) assigned to each pin.  Keeping both in your head at the same time while trying to assign pins is less than thrilling.

So, I merged the two into carefully constructed spreadsheets, added buckets of color, and came up with these diagrams, which make life infinitely easier.

I’ll make a set of A3 chip-level spreadsheets soon, but for now these are the version I’ve completed.  The -DIP variants are synchronized to the DIP adapters that are part of the DorkbotPDX group PCB order and will be available for sale in a few weeks at my to-be-set-up webshop.


Xmega adapter boards for breadboarding


I’ve got a number of projects coming up that would be radically simplified by a) using ATXmega parts, and b) breadboarding a prototype.  The problem is that Xmega’s don’t come in anything but surface-mount packages.  The obvious solution is to construct an adapter board.  A straight pin conversion would be a waste of effort, so adding programming headers, clocks, and decoupling capacitors is a necessity.

I posted to the DorkbotPDX list to see if anybody is interested in ordering some of these alongside my own order in the next group PCB buy (April 26th), and got one response almost immediately.  As a result I’m going to tweak the boards up and make sure they’re ready to go, and post them up here for comments.

The first board here is the ATxmega*A4 unit, which is a 40-pin 600-mil DIP.  PDI header on the right, crystal on the left, decoupling and AVCC filter caps scattered around.  Port pins are labeled as are + and -.  PDI pins are accessible on the main header as well as the programming header.  Discretes are all 0603 for ease of assembly, though the chip itself is a QFN (unfortunately).

The second board is a straight extrapolation of the first, designed for the larger A3 chips.  It’s a 60-pin 600-mil DIP with the same basic feature set.

I’ll be tweaking these over the next few days, and hopefully producing a batch of them in the next couple weeks.