Get More I/O Now! Going Beyond Your MCU's Pin Count

Small microcontroller design projects often require additional I/O. In this article, Joseph presents several methods of expanding digital and analog I/O for these applications.

- Joseph Corleto

He delves into some of the most common options, such as adding a shift register, a multiplexer, or an I/O expander, along with a few less conventional approaches. You could have as much I/O as your heart desires yet some approaches come with cost, size and development time tradeoffs.

It seems like microcontroller memory just gets bigger and bigger, and often, it doesn't make a significant dent in program space. When I mention this to the players in the firmware game that have been doing this for a while, they are quick to say how lucky we 'youngins' are to have limitless memory so that even the most inefficient code can get the job done right.

And they are correct! I seldom need to optimize my code for limited program space. For speed, yes, I do sometimes need to be sensitive to certain places in my program, but not for the entire program space. Instead, I can focus on abstracting my program such that it has multiple layers of files that nearly anyone can read without a hassle.

Even when I'm developing small microcontroller projects, I typically use only a small part of the memory, while still maintaining the price point the product is supposed to hit.

But for the amount of I/O, this is a completely different story.

In fact, I often find myself needing more digital and even analog inputs and outputs. Sure, I could just upsize and get a bigger microcontroller, but this is rarely the solution, because the microcontroller seems to be locked down.