Test circuit to test the shared data pins using Keyboard and LCD libraries
Circuit parameters:
Security entry system with no false positives...
Generic 4x4 keypad to enter the password...
Generic LCD (4478 compatible) to display key press and other messages...
Piezo sounder and led to provide feedback...
Parts:
Arduino Uno (rev 3)...
Keypad: Generic 4x4 matrix keypad...
LCD: DEM20485SYH (20 character by 4 lines)...
Discrete components: 330R resistor, Led, 10k pot for LCD contrast...
Conclusion:
Circuit works perfectly, occasional spurious characters on LCD during lcd.clear() but nothing to worry about...
Notes:
Used the keyboard interrupt to facilitate better timing of events...
The lcd.clear() timing is quite long and erroneous characters can occur, however this is also true of circuits that do not share data pins... it's all down to timing and that's another day...
Any tips on how to prevent erroneous characters on LCD appreciated...
Mike
Link to test circuit: http://www.phpbbireland.com/kiss2/viewtopic.php?f=79&t=265