This guide will show you how to install a bootloader and update the Marlin firmware on your Ender 3 or Ender 3 Pro.

Why update your Ender 3's firmware?

Most Ender 3s ship with a customized, outdated Marlin firmware version that lacks thermal runaway protection and other safety features.

If you use OctoPrint, you may even have seen the following error message: "Warning! Your printer's firmware is known to lack mandatory safety features (e.g. thermal runaway protection). This is a fire risk." Many 3D printer fires happen as a result of thermal runaway.

Mentioned here OctoPrint: Control Your 3D Printer Remotely with Raspberry Pi and OctoPi Untether your printer!

What is thermal runaway?

In a nutshell, your printer contains both a temperature sensor, or "thermocouple", and a heating element. When you start a print, your heating element reads data from the thermocouple and continues to heat until reaching the predefined print temperature. Thermal runaway is a condition that exists when the thermocouple becomes dislodged or damaged and your printer continues heating, forever, until something like this happens (read: 🔥🔥🔥):

What is thermal runaway protection?

Thermal runaway protection is a feature of most modern firmware that shuts down the heating element if the thermocouple isn't responding properly. To get technical, it generally polls for a temperature change every N seconds and expects an increase. No increase? Shut it down.

Guide overview

Before updating the Creality Ender 3 firmware, we'll load a custom bootloader onto the Ender 3 using a cheap Arduino Uno or Arduino Uno clone. You can pick an Uno up for about $15 on Amazon.

What's a bootloader?

A bootloader is a program that loads an operating system when a computer (in this case, the printer) is turned on. Because the Ender 3 doesn't come with a bootloader, we'll need to install one. This will allow the printer to boot using a newer version of the Marlin firmware. After installing the bootloader, we'll be able to easily update the firmware in the future, too.

This guide will work for Mac, Windows, and Linux!

Let's get started!