Update README.md

README.md

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-# s2.1
-First interrupt example
+### Button edge Events
+The repository [s2.1]{https://github.com/kf5011/s2.1} uses a falling and rising edge interrupt on each of the two buttons on the base board.
+
+1. Run the program and examine it's behaviour.  (You'll need the serial-monitor to see the output from the print statements)
+2. Pay close attention to when the actions occur, when the button is pressed or released.
+
+1. Identify the input pins related to the buttons and the 5-way joystick on the shield.
+2. Each pin can have an interrupt for the rising-edge and falling-edge signal, a total of 14 possible interrupts.
+3. Investigate the actions of the interrupts for the base-board switches and the 5-way switch.  What differences can you see?