The keypad uses an onboard ATMega328P to scan the matrix for button presses, decode them, and send them via UART or I²C to an Arduino. [ELECTRONOOBS] has the PCB files available via Patreon for ...

In this case, you’ll be losing all of your nickels to an Arduino Pro ... across the matrix. There’s even a piezo buzzer for victory squawks. We only wish the button under the handle were ...