The blink plug is a small board with two LEDs and two miniature pushbuttons.
A trick is used to connect everything using only two I/O pins: the buttons are connected to the same pins as the LEDs and they tie that pin to ground when pushed. To avoid short circuits, the I/O pin must be configured either as input (with pull-up) or as 0-level output, but never as 1-level output.
This design has as side-effect that while a button is pressed the corresponding LED will light up regardless of the state of the I/O pin. You may consider this to be either a feature or a bug ;)
There is nothing to configure.
The top red LED w/ button are tied to AIO, the bottom green one w/ button to DIO.
Dimensions: 21.1 x 21.6 mm
CadSoft EAGLE design files: see below.
This plug can be operated at 5V as well as 3.3V.
This board uses the conventions of a JeePlug and can be used with the ports on a JeeNode. It can also be used with other boards and MCU's, if you hook it up properly and adapt the interface code for it.