This script is designed to control a PDSP (or HDSP) type display using Python
when connected to a Raspberry Pi.
Things to do:
* more flexible input via args (currently, using statically defined variable)
* gracefully handle SIG-INT (ctrl-c) and clear display upon exit
* for PBC - rearrange header pins to group unused pins so that a 1x6 header can be used
This code is based on Arduino code from http://www.nycresistor.com/2010/05/30/working-with-the-hdsp-2111/