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APSP_demo.ino
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this sample code tests the Gtronics.NET Arduino Proto Shield Plus buttons, LCD, POT and LEDs functionality:

- The button pressed is shown on the LCD display
in addition:
- pressing "A-SELECT" button turns on the GRN LED
- pressing "B-LEFT" button turns on the RED LED
- POT value is shown on the LCD as an 8bit ADC value
- LCD backlight brightness is related to the POT value
