If you want to add a keypad to your Arduino project, the options are pretty limited. There’s that red and blue 4×4 membrane we’ve all seen in password-protected door lock projects,… ...

If a keypad has 12 keys, it is wired as 3 columns by 4 rows. A 16 key pad would have 4 columns by 4 rows. ... We can now start the real experiment with as Arduino Uno by wiring up the keypad to the ...

From there you get the virtual keypad seen above for typing out the phone number or composing a message. [Thanks Victorzie] Posted in Arduino Hacks , Cellphone Hacks Tagged cellphone , GPRS ...