How to call functions when a key changes it's state

Dependencies:   Hotboards_keypad mbed

Revision:
0:a2b95a8cb722
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Hotboards_keypad.lib	Tue Mar 08 20:46:03 2016 +0000
@@ -0,0 +1,1 @@
+http://developer.mbed.org/users/Hotboards/code/Hotboards_keypad/#e870110f753b