This first-year group project started with a simple brief: build a keypad-controlled digital lock using a Raspberry Pi. It was a small project, but a very rewarding one, and it introduced me to some great people. Ultimately, our project was chosen by the lecturer to be demonstrated at subsequent university open days.
The main constraint was that we were not allowed to rely on interrupt-driven input for the membrane keypad. Instead, we had to detect key presses by polling the Pi’s pins and working through the keypad matrix ourselves. On top of the basic four-digit passcode entry, we added status LEDs for correct and incorrect codes, a short delay after failed attempts to make brute forcing less practical, and a text-based interface for changing settings after the user had gained access. We also wrote software to attack our own system by generating electrical signals that mimicked key presses.
All in all, we built something tangible and learnt a lot about low-level I/O, simple security logic, physical hardware integration, and a bit of interface design.