Marlin firmware optimized for the Anycubic i3 Mega 3D printer
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Anycubic i3 Mega Marlin 1.1.9 by davidramiro

This is my slightly customized version of the Marlin Firmware, gratefully based on derhopp's repo with his remarkable efforts to get the Anycubic i3 Mega TFT screen to work.

Feel free to discuss issues and work with me further optimizing this firmware!

I am running this version on an i3 Mega Ultrabase V3 (for distinction of the different versions, check this Thingiverse thread). Basically, this should work on every Ultrabase version that has two Z-axis endstops.

The new Mega-S is not officially supported. You can try your luck, but I have no means of troubleshooting issues with that machine. E-steps need to be set to 384 (M92 E384.00 + M500), and afterwards calibration is highly recommended as per the instructions on the Wiki.

Note: This is just a firmware, not magic. A big part of print quality still depends on your slicer settings and mechanical condition of your machine.

Make sure to take a look at the Wiki, especially the FAQ.

Known issues:

  • Cura users: Please turn off jerk and acceleration control in your print settings (not visible by default, select advanced visibility to unlock them). Cura's high default jerk and acceleration might cause shifted layers if you use TMC2208.
  • Estimated print times from your slicer might be slightly off.
  • Special characters on any file or folders name on the SD card will cause the file menu to freeze. Simply replace or remove every special character (Chinese, Arabic, Russian, accents, German & Scandinavian umlauts, ...) from the name. Symbols like dashes or underscores are no problem. Important note: On the SD card that comes with the printer there is a folder with Chinese characters in it by default. Please rename or remove it.
  • Cancelling prints via display is buggy sometimes, simply reboot the printer when the menu shows an error. Protip: Switch to OctoPrint.

Why use this?

While the i3 Mega is a great printer for its price and produces fantastic results in stock, there are some issues that are easily addressed:

  • Many people have issues getting the Ultrabase leveled perfectly, using Manual Mesh Bed Leveling the printer generates a mesh of the flatness of the bed and compensates for it on the Z-axis for perfect prints without having to level with the screws.
  • Much more efficient bed heating by using PID control. This uses less power and holds the temperature at a steady level. Highly recommended for printing ABS.
  • Fairly loud fans, while almost every one of them is easily replaced, the stock FW only gives out 9V instead of 12V on the parts cooling fan so some fans like Noctua don't run like they should. This is fixed in this firmware.
  • Even better print quality by adding Linear Advance, S-Curve Acceleration and some tweaks on jerk and acceleration.
  • Thermal runaway protection: Reducing fire risk by detecting a faulty or misaligned thermistor.
  • Very loud stock stepper motor drivers, easily replaced by Watterott or FYSETC TMC2208. To do that, you'd usually have to flip the connectors on the board, this is not necessary using this firmware.
  • No need to slice and upload custom bed leveling tests, simply start one with a simple G26 command.
  • Easily start an auto PID tune or mesh bed leveling via the special menu (insert SD card, select special menu and press the round arrow)
  • Filament change feature enabled: Switch colors/material mid print with M600 (instructions below)

How to flash this?

I provided three different precompiled hex files: One for no modifications on the stepper motor drivers - good for people who didn't touch anything yet, one for boards with TMC2208 installed and where the connectors have been flipped and one with TMC2208 and the connectors in original orientation.

Choose your precompiled hex:

  • Download the precompiled firmware here: Releases
  • Choose the correct hex file:
  • For TMC2208 with connectors in original orientation, use Marlin-AI3M-XXXXXX-TMC2208.hex
  • If you use TMC2208 and already reversed your connectors, use Marlin-AI3M-XXXXXX-TMC2208_reversed.hex
  • If you use a newer version of the TMC2208 that doesn't require the connector to be reversed (TMC2208 "v2.0" written on the PCB, chip on the top side), please also use Marlin-AI3M-XXXXXX-TMC2208_reversed.hex.
  • If you use the original stepper motor drivers, use Marlin-AI3M-XXXXXX-stock_drivers.hex.

Or compile it yourself:

  • Download Arduino IDE
  • Clone or download this repo
  • In the IDE, under Tools -> Board select Genuino Mega 2560 and ATmega2560
  • Open Marlin.ino in the Marlin directory of this repo
  • Customize if needed (e.g. motor directions and type at line 559 to 566 and line 857 to 865 in Configuration.h)
  • Under Sketch, select Export compiled binary
  • Look for the .hex file in the Marlin directory (only use the Marlin.ino.hex, not the Marlin.ino.with_bootloader.hex!)

After obtaining the hex file:

  • Flash the hex with Cura, OctoPrint or similar
  • Use a tool with a terminal (OctoPrint, Pronterface, Repetier Host, ...) to send commands to your printer.
  • Connect to the printer and send the following commands:
  • M502 - load hard coded default values
  • M500 - save them to EEPROM

Calibration and other instructions have been moved to the Wiki.

Manual Mesh Bed Leveling

If you have issues with an uneven bed, this is a great feature.

  • Insert an SD card, enter the print menu.
  • Enter the special menu by selecting it and pressing the round arrow:

Special Menu

  • In this menu, the round arrow is used to execute the command you selected.
  • Preheat the bed to 60°C with this entry: (if you usually print with a hotter bed, use the Anycubic menu)

Preheat bed

  • Level your preheated bed as well as you can with the four screws.
  • Start the mesh leveling:

Start MMBL

  • Your nozzle will now move to the first calibration position.
  • Don't adjust the bed itself with screws, only use software from here on!
  • Use a paper - I recommend using thermopaper like a receipt or baking paper
  • Use the onscreen controls to lower or raise your nozzle until you feel a light resistance: (If you want to send the same command multiple times, select the item again, even though it is still marked red.)

Z axis controls

  • Once finished , move to the next point:

Next mesh point

  • Repeat the last two steps until all 25 points are done.
  • Your printer will beep, wait 20 seconds and then save:

Save to EEPROM

  • Reboot your printer.

After leveling:

  • Reboot the printer.
  • To ensure your mesh gets used on every print from now on, go into your slicer settings and look for the start GCode
  • Look for the Z-homing (either just G28 or G28 Z0) command and insert these two right underneath it:
M420 S1
  • Enjoy never having to worry about an uneven bed again!

Manual commands for use with OctoPrint etc.:

  • G29 S1 - Start MMBL
  • G29 S2 - Next Mesh point
  • Raising Z: G91, G1 Z0.02, G90 (one after another, not in one line)
  • Lowering Z: G91, G1 Z-0.02, G90
  • After seeing ok in the console, send M500 to save.

Testing your bed leveling

  • No need to download or create a bed leveling test, simply send those commands to your printer:
G26 C H200 P25 R25
  • To adjust your filament's needed temperature, change the number of the H parameter
  • If your leveling is good, you will have a complete pattern of your mesh on your bed that you can peel off in one piece
  • Don't worry if the test looks a bit messy, the important thing is just that the line width is the same all over the mesh
  • Optional: Hang it up on a wall to display it as a trophy of how great your leveling skills are.

M600 Filament Change

M600 Demo

A USB host (OctoPrint, Pronterface, ...) is required to use this.


  • Send M603 L0 U0 to use manual loading & unloading.
  • Send M603 L530 U555 to use automatic loading & unloading
  • Save with M500

Filament change process (manual loading):

  • Place M600 in your GCode at the desired layer or send it manually
  • The nozzle will park and your printer will beep
  • Remove the filament from the bowden tube
  • Insert the new filament right up to the nozzle, just until a bit of plastic oozes out
  • Remove the excess filament from the nozzle with tweezers
  • Send M108 via your USB host.
  • Note for OctoPrint users: After sending M108, enable the advanced options at the bottom of the terminal and press Fake Acknowledgement

Filament change process (automatic loading):

  • Place M600 in your GCode at the desired layer or send it manually
  • The nozzle will park
  • The printer will remove the filament right up to the extruder and beep when finished
  • Insert the new filament just up to the end of the bowden fitting, as shown here:

Load Filament

  • Send M108 via your USB host.
  • Note for OctoPrint users: After sending M108, enable the advanced options at the bottom of the terminal and press Fake Acknowledgement
  • The printer will now pull in the new filament, watch out since it might ooze quite a bit from the nozzle
  • Remove the excess filament from the nozzle with tweezers


Back up & restore your settings

Some updates require the storage to be cleared (M502), if mentioned in the update log. In those cases, before updating, send M503 and make a backup of all the lines starting with:


After flashing the new version, issue a M502 and M500. After that, enter every line you saved before and finish by saving with M500.

Detailed changes:

  • Thermal runaway protection enabled and tweaked
  • Manual mesh bed leveling enabled (check this link to learn more about it)
  • Heatbed PID mode enabled
  • TMC2208 configured in standalone mode
  • Stepper orientation flipped (you don't have to flip the connectors on the board anymore)
  • Linear advance unlocked (Off by default. Research, calibrate and then enable with M900 Kx)
  • S-Curve Acceleration enabled
  • G26 Mesh Validation enabled
  • Some redundant code removed to save memory
  • Minor tweaks on default jerk and acceleration
  • Printcounter enabled (M78)
  • M600 filament change feature enabled

Changes by derhopp:

  • 12V capability on FAN0 (parts cooling fan) enabled
  • Buzzer disabled (e.g. startup beep)
  • Subdirectory support: Press the round arrow after selecting a directory
  • Special menu in the SD file menu: Press the round arrow after selecting Special menu

About Marlin

Marlin is an optimized firmware for RepRap 3D printers based on the Arduino platform. First created in 2011 for RepRap and Ultimaker printers, today Marlin drives a majority of the world's most popular 3D printers. Marlin delivers outstanding print quality with unprecedented control over the process.

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Contributing to Marlin

If you have coding or writing skills you're encouraged to contribute to Marlin. You may also contribute suggestions, feature requests, and bug reports through the Marlin Issue Queue.

Before contributing, please read our Contributing Guidelines and Code of Conduct.

Marlin Resources


Marlin's administrators are:

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Marlin is published under the GPLv3 license because we believe in open development. The GPL comes with both rights and obligations. Whether you use Marlin firmware as the driver for your open or closed-source product, you must keep Marlin open, and you must provide your compatible Marlin source code to end users upon request. The most straightforward way to comply with the Marlin license is to make a fork of Marlin on Github, perform your modifications, and direct users to your modified fork.