Microcontroller vs. microprocessor #

Both microcontrollers and microprocessors are small chunks of silicon encased in black plastic with little wires or metal balls sticking out of them. They both act like little brains. The difference is that microcontrollers have memory and other circuitry embedded on the same silicon chip that can do stuff like talk to a USB port or send pulses to motor. Unfortunately, virtually all microprocessors now have at least some memory caches embedded in them, and they get additional peripherals added constantly.

In practice, people use the words interchangeably, but the ones that are small, cheap, and not in a desktop, laptop, tablet, or phone, people tend to call microcontrollers. As mechanical engineers, you’ll probably use microcontrollers to build small electromechanical systems. For example, as a mechanical engineer, you might be asked to work on

• a test chamber that has a temperature sensor in it, with a microcontroller that monitors the temperature and runs a fan if it gets too hot inside
• a pump controller that regulates fuel pressure in a booster rocket
• an gearbox that includes an encoder that displays the velocity of the output shaft on an LCD

Two big categories of microcontroller #

Category 1: no operating system #

The most ubiquitous small microcontroller in the last decade is the Arduino. It has no operating system. When you power up an Arduino out of the box, it has a simple program called a bootloader on it that just does this: it checks the USB port to see if any computer is waiting to send it new code. If there’s no new code, it runs whatever code was last sent to it. That’s it. Everything else you want it to do, you either have to write yourself, or you have to use a library that somebody else wrote.

Here’s what an Arduino Uno looks like.

In previous offerings of this course, we have used an Arduino MKR 1010 Wifi which is like the Uno, but more faster, smaller, and with wifi.

In Fall 2023, you have an Adafruit KB2040 in your project kit, which is also like the Arduino, but made by a different company and with a different central processing chip - called an RP2040.

Category 2: has an operating system #

The Raspberry Pi is even more widespread than the Arduino, but it’s more of a small computer than just a microcontroller. When you power up a Raspberry Pi, it also runs a bootloader, but that bootloader loads an operating system, usually Linux, from a microSD card on the Pi. The operating system does all sorts of stuff for you: gives you a filesystem, sets up network connections, allows the CPU to switch back and forth so lots of different programs can run at the same time. The Pi also comes preloaded with a ton of software.