Configure Raspberry Pi OS securely with a custom account, SSH keys, locale, I²C or SPI interfaces, correct power, updates, and safe shutdown.
A practical walkthrough of the keypad-reading code via the Keypad.h library: makeKeymap, row/column pin arrays, and the getKey function.
A general explanation of the Micro SD card reader module: the SPI protocol, voltage conversion, and wiring it to Arduino via the standard SD library.
An explanation of ASK modulation in 433MHz RF modules, and wiring them to Arduino via the RadioHead ASK library.