Anycubic i3 Mega Marlin Firmware with TFT support

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) with FYSETC TMC2208 V1.2 installed. Basically, this should work on every Ultrabase version that has no bed leveling sensor and two Z-axis endstops.

Why use this?

While the i3 Mega is a great printer for it's 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 planeness 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 enabling 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)

Known issues:

• 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.

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:

• Choose the correct hex file:
• For TMC2208 with connectors in original orientation, use Marlin-AI3M-XXXXXX-TMC2208.hex
• For TMC2208 with flipped connectors, use Marlin-AI3M-XXXXXX-TMC2208_flipped.hex
• If you use the original stepper motor drivers, use Marlin-AI3M-XXXXXX-stock_drivers.hex.
• If you use a newer version of the TMC2208 that doesn't require the connector to be flipped (e.g. BIQU TMC2208, KINGPRINT TMC2208), please use Marlin-AI3M-XXXXXX-TMC2208_flipped.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 and under Sketch, select Export compiled binary
• Look for the .hex file in your temporary directory, e.g. .../AppData/Local/Temp/arduino_build_xxx/ (only the Marlin.ino.hex, not the Marlin.ino.with_bootloader.hex!)

After obtaining the hex file:

• Flash the hex with Cura, OctoPrint or similar
• Connect to the printer and send the following commands:
• M502 - load hard coded default values
• M500 - save them to EEPROM

After flashing:

This firmware is perfectly calibrated for my own machine with TMC2208 (1.015V on the axis, 1.152V on the extruder). If you also have these stepper motor drivers and you run them on similar voltages, this firmware should do great prints right after flashing. Nevertheless, a PID tune and especially calibrating the extruder is highly recommended. Simply follow the instructions below.

Calibrating extruder steps

• Preheat the hotend with M104 S200
• Use a caliper or measuring tape and mark 120mm (measured downwards from the extruder intake) with a pencil on the filament
• Send G91, G1 E100 F300 and G90 in that order
• Your extruder will feed 100mm of filament now
• Measure where your pencil marking is now. If it's exactly 20mm to the extruder, it's perfectly calibrated
• If it's less or more than 20mm, add or subtract that value from 100mm, e.g.:
• If you measure 25mm, your result would be 95mm. If you measure 15mm, your result would be 105mm
• Calculate your new value: ( 100mm / actually extruded filament ) * 92.6
• For example, if your markings are at 15mm, you'd calculate: (100/105) * 92.6 = 88.19
• Put in the new value like this: M92 X80.00 Y80.00 Z400.00 Exxx.xx, replacing x with your value
• Save with M500

PID tuning

• Turn on parts cooling fan, I recommend running it at 70% because of the 12V mod (M106 S191)
• Send M303 E0 S230 C8 U1 to start extruder PID auto tuning
• Wait for it to finish
• Send M303 E-1 S80 C8 U1 to start heatbed PID auto tuning
• Wait for it to finish
• Save with M500, turn off fan with M106 S0

Reminder: PID tuning sometimes fails. If you get fluctuating temperatures or the heater even fails to reach your desired temperature, you can always go back to the stock settings by sending M502 and M500.

Bonus: Manual Mesh Bed Leveling

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

• Level your preheated bed as well as you can
• Send G29 S1, your nozzle will go 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 or a tool like OctoPrint to lower or raise your nozzle until you feel a light resistance
• If 0.1mm steps are not enough, you can send specific commands down to 0.02mm via those three commands:
• To raise: G91, G1 Z+0.02, G90
• To lower: G91, G1 Z-0.02, G90
• When done, send G29 S2 and repeat the process for the next level point. Continue with G29 S2every time.
• After finishing the 25 points, the printer will beep and calculate. After seeing ok on the console, send these two commands to your printer:

M420 S1
M500

• 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:

M501
M420 S1

• Enjoy never having to worry about an uneven bed again!

Testing your bed leveling

• No need to download or create a bed leveling test, simply send those commands to your printer:

G28
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
• Optional: Hang it up on a wall to display it as a trophy of how great your leveling skills are.

Detailed changes:

• Thermal runaway protection enabled
• Stepper orientation flipped (you don't have to flip the connectors on the board anymore)
• Linear advance enabled (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
• Manual mesh bed leveling enabled (check this link to learn more about it)
• Heatbed PID mode enabled
• Minor tweaks on default jerk and acceleration
• 12V capability on FAN0 (parts cooling fan) enabled
• No startup beep

Menu mods by derhopp:

• 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.

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 Home Page - The latest Marlin documentation.
• Marlin Releases - All Marlin releases with release notes.
• RepRap.org Wiki Page - An overview of Marlin and its role in RepRap.
• Marlin Firmware Forum - Get help with configuration and troubleshooting.
• Marlin Firmware Facebook group - Help from the community. (Maintained by @thinkyhead.)
• @MarlinFirmware on Twitter - Follow for news, release alerts, and tips. (Maintained by @thinkyhead.)

Credits

Marlin's administrators are:

• Scott Lahteine [@thinkyhead]
• Roxanne Neufeld [@Roxy-3D]
• Bob Kuhn [@Bob-the-Kuhn]
• Erik van der Zalm [@ErikZalm]

Notable contributors include:

• Alexey Shvetsov [@alexxy]
• Andreas Hardtung [@AnHardt]
• Ben Lye [@benlye]
• Bernhard Kubicek [@bkubicek]
• Bob Cousins [@bobc]
• Petr Zahradnik [@clexpert]
• Jochen Groppe [@CONSULitAS]
• David Braam [@daid]
• Eduardo José Tagle [@ejtagle]
• Ernesto Martinez [@emartinez167]
• Edward Patel [@epatel]
• F. Malpartida [@fmalpartida]
• João Brazio [@jbrazio]
• Kai [@Kaibob2]
• Luc Van Daele [@LVD-AC]
• Alberto Cotronei [@MagoKimbra]
• Marcio Teixeira [@marcio-ao]
• Chris Palmer [@nophead]
• Chris Pepper [@p3p]
• Steeve Spaggi [@studiodyne]
• Thomas Moore [@tcm0116]
• Teemu Mäntykallio [@teemuatlut]
• Nico Tonnhofer [@Wurstnase]
• [@android444]
• [@bgort]
• [@GMagician]
• [@Grogyan]
• [@maverikou]
• [@oysteinkrog]
• [@paclema]
• [@paulusjacobus]
• [@psavva]
• [@Tannoo]
• [@TheSFReader]
• ...and many others

License

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.