Atmel AT90USBKey Headers and Squid Cables

Headers for port access on the Atmel AT90USBKey
Headers for port access on the Atmel AT90USBKey

I’ve got a little fun project where I need to create a USB HID keyboard device. I searched high and low for an STK526 mezzanine board for my STK500 development platform so I could work with the ATmega32U2 chip.  Failing to find one, I purchased an Atmel AT90USBKey.  It seems like a decent, inexpensive little development platform except for one thing.


I’m not sure what they  were smoking in Norway when they were designing this board, but they used a unique  header footprint for the 2×5 port headers.  The pin pitch is a standard 0.050″, but the row spacing is 0.100.  There are no commercially available pin headers or ribbon cable connectors in that configuration available.

You can either attempt to solder wires to the extremely small pads, or you can make or purchase “wings” for your development board.  I chose yet another path.

You can get 2×5 pin headers in 0.050″ pitch but they have the standard 0.050″ row spacing.  Looking at the offerings from Digikey, I saw some surface mount pin headers that looked like they might be adapted to fit, so I purchased some of the headers (P/N S9012E-05-ND) as well as some 12″ ribbon cables with the mating connectors already attached to each end (P/N SAM8219-ND)

To get the pin headers to fit, one row of legs was bent straight.  The still bent row was then inserted into one of the header spots on the board and tacked into place by soldering one of the center pins.  I attached a ribbon cable and connector to the header and used this to help bend the header until the straightened row of pins was touching the other row of plated-through holes on the board.  The header was then soldered into place.

Because of the way they are soldered on, the pin headers are not vertical, but sit at about a 45º angle.  Turns out this is actually a good thing as the ribbon cable connectors are too wide to fit the board’s header layout if all of the connectors align.

Squid cables and headers for an Atmel AT90USBKeyThe last step was to cut the ribbon cables in half, flay the ends, and crimp on standard female 0.025″ square post terminals.

Squid cables and headers for an Atmel AT90USBKey