The Uno also has a limited number of pins, making it difficult to work with when the project requires plenty of input and output components. However, these two areas are where the Arduino Mega shines.

But what if the Arduino Uno was released in 1980 ... No USB-UART (which also means no USB programming), a different pin layout (Arduino shields likely won’t fit) and more I/Os than the ATmegas ...

[Rafael] just made a little library that allows you to interface these modules to the Atmega328p-based Arduino UNO in order to gain ... Arduino platform. The 30-pin SIMM shown above is capable ...