The keypad I want to replace is 16 keys in the form of 4 rows and 4 columns. Making LCD with touch screen is easy, divide the touch area into grid of 16 but how can I tell Arduino how to signal the key press on 4 rows and 4 columns wire? For example if I touch a 6, how can I make Arduino connect row 2, column 3 together? At present the only way I can think of is something like N.O. analog switch like CMOS 4066.
Also can someone point me to quick guide on Arduino with color touchscreen LCD + SD card for loading background image.
Lastly, since LCD and SD card on Arduino Mega line seems to be all 3.3v Would the 4066 handle it gracefully since the keypad is on 5v system? 4066 itself can operate from 3v to 15v but I don’t know if having 3v input to switch control would be enough or if I’d need to cheat with a pullup to 5v. Or can I have the 4066 on 3.3v supply and let the in/out handle the 5v?