This is a working release, which was tested with an Arduino Pro Mini and Raspberry Pi. The Pro Mini is soldered onto breadboard and will be available at the space soon.
Note
This code does not currently actuate a door lock, although it will be simple to add this feature. At present, the only way to know that it's all working is by observation of the serial console output from either the RPi or the Arduino itself. Once the method of actuating the lock is known, this can be added into the loop function where the success beep is sounded .