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Release status: working

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a firmware for arduino compatible setups
CAD Models
External Link

The leading developers of Marlin are currently EvdZ and bkubicek, though many others contribute with their patches. This is a firmware for reprap single-processor electronics setups. It also works on the Ultimaker PCB. It supports printing from SD card+Folders, and look-ahead trajectory planning. This work is licensed under the GNU GPL v3 or (at the user's discretion) any later version. It is based on Sprinter firmware, which was licensed under GPL v2 or later.

Current Version: beta 1 of v1.0.0:

See Marlin on Github.

Works on Ultimaker and Sanguinololu, maybe? working on Generation_6_Electronics, and maybe other setups.

Quick Information

This RepRap firmware is a mashup between Sprinter, grbl and many original parts.

Derived from Sprinter and Grbl by Erik van der Zalm. Sprinters lead developers are Kliment and caru. Grbls lead developer is Simen Svale Skogsrud. Sonney Jeon (Chamnit) improved some parts of grbl A fork by bkubicek for the Ultimaker was merged, and further development was aided by him. Some features have been added by: Lampmaker, Bradley Feldman, and others...


  • Interrupt based movement with real linear acceleration
  • High steprate
  • Look ahead (Keep the speed high when possible. High cornering speed)
  • Interrupt based temperature protection
  • preliminary support for Matthew Roberts advance algorithm For more info see:
  • Full endstop support
  • SD Card support
  • SD Card folders (works in pronterface)
  • LCD support (ideally 20x4)
  • LCD menu system for autonomous SD card printing, controlled by an click-encoder.
  • EEPROM storage of e.g. max-velocity, max-acceleration, and similar variables
  • many small but handy things originating from bkubicek's fork.
  • Arc support
  • Temperature oversampling
  • Dynamic Temperature setpointing aka "AutoTemp"
  • Support for QTMarlin, a very beta GUI for PID-tuning and velocity-acceleration testing.
  • Endstop trigger reporting to the host software.
  • Updated sdcardlib
  • Heater power reporting. Useful for PID monitoring.

The default baudrate is 250000. This baudrate has less jitter and hence errors than the usual 115200 baud, but is less supported by drivers and host-environments.

Differences and additions to the already good Sprinter firmware


Marlin has look-ahead. While sprinter has to break and re-accelerate at each corner, lookahead will only decelerate and accelerate to a velocity, so that the change in vectorial velocity magnitude is less than the xy_jerk_velocity. This is only possible, if some future moves are already processed, hence the name. It leads to less over-deposition at corners, especially at flat angles.

Arc support:

Splic3r can find curves that, although broken into segments, were ment to describe an arc. Marlin is able to print those arcs. The advantage is the firmware can choose the resolution, and can perform the arc with nearly constant velocity, resulting in a nice finish. Also, less serial communication is needed.

Temperature Oversampling:

To reduce noise and make the PID-differential term more useful, 16 ADC conversion results are averaged.


If your gcode contains a wide spread of extruder velocities, or you realtime change the building speed, the temperature should be changed accordingly. Usually, higher speed requires higher temperature. This can now be performed by the AutoTemp function By calling M109 S T F you enter the autotemp mode.

You can leave it by calling M109 without any F. If active, the maximal extruder stepper rate of all buffered moves will be calculated, and named "maxerate" [steps/sec]. The wanted temperature then will be set to t=tempmin+factor*maxerate, while being limited between tempmin and tempmax. If the target temperature is set manually or by gcode to a value less then tempmin, it will be kept without change. Ideally, your gcode can be completely free of temperature controls, apart from a M109 S T F in the start.gcode, and a M109 S0 in the end.gcode.


If you know your PID values, the acceleration and max-velocities of your unique machine, you can set them, and finally store them in the EEPROM. After each reboot, it will magically load them from EEPROM, independent what your Configuration.h says.

LCD Menu:

If your hardware supports it, you can build yourself a LCD-CardReader+Click+encoder combination. It will enable you to realtime tune temperatures, accelerations, velocities, flow rates, select and print files from the SD card, preheat, disable the steppers, and do other fancy stuff. One working hardware is documented here: Also, with just a 20x4 or 16x2 display, useful data is shown.

SD card folders:

If you have an SD card reader attached to your controller, also folders work now. Listing the files in pronterface will show "/path/subpath/file.g". You can write to file in a subfolder by specifying a similar text using small letters in the path. Also, backup copies of various operating systems are hidden, as well as files not ending with ".g".

Endstop trigger reporting:

If an endstop is hit while moving towards the endstop, the location at which the firmware thinks that the endstop was triggered is outputed on the serial port. This is useful, because the user gets a warning message. However, also tools like QTMarlin can use this for finding acceptable combinations of velocity+acceleration.

Coding paradigm:

Not relevant from a user side, but Marlin was split into thematic junks, and has tried to partially enforced private variables. This is intended to make it clearer, what interacts which what, and leads to a higher level of modularization. We think that this is a useful prestep for porting this firmware to e.g. an ARM platform in the future. A lot of RAM (with enabled LCD ~2200 bytes) was saved by storing char []="some message" in Program memory. In the serial communication, a #define based level of abstraction was enforced, so that it is clear that some transfer is information (usually beginning with "echo:"), an error "error:", or just normal protocol, necessary for backwards compatibility.

Interrupt based temperature measurements:

An interrupt is used to manage ADC conversions, and enforce checking for critical temperatures. This leads to less blocking in the heater management routine.

Non-standard M-Codes, different to an old version of sprinter:


  • G2 - CW ARC
  • G3 - CCW ARC


  • M17 - Enable/Power all stepper motors. Compatibility to ReplicatorG.
  • M18 - Disable all stepper motors; same as M84.Compatibility to ReplicatorG.
  • M30 - Print time since last M109 or SD card start to serial
  • M42 - Change pin status via gcode
  • M80 - Turn on Power Supply
  • M81 - Turn off Power Supply
  • M114 - Output current position to serial port
  • M119 - Output Endstop status to serial port

Movement variables:

  • M202 - Set max acceleration in units/s^2 for travel moves (M202 X1000 Y1000) Unused in Marlin!!
  • M203 - Set maximum feedrate that your machine can sustain (M203 X200 Y200 Z300 E10000) in mm/sec
  • M204 - Set default acceleration: S normal moves T filament only moves (M204 S3000 T7000) im mm/sec^2 also sets minimum segment time in ms (B20000) to prevent buffer underruns and M20 minimum feedrate
  • M220 - set build speed mulitplying S:factor in percent ; aka "realtime tuneing in the gcode". So you can slow down if you have islands in one height-range, and speed up otherwise.
  • M301 - Set PID parameters P I and D
  • M400 - Finish all buffered moves.


  • M200 - Set filament diameter for advance
  • M205 - advanced settings: minimum travel speed S=while printing T=travel only, B=minimum segment time X= maximum xy jerk, Z=maximum Z jerk


  • M500 - stores paramters in EEPROM
  • M501 - reads parameters from EEPROM (if you need reset them after you changed them temporarily).
  • M502 - reverts to the default "factory settings". You still need to store them in EEPROM afterwards if you want to.

Configuring and compilation:

Install the arduino software IDE/toolset v22

For gen6 and sanguinololu the Sanguino directory in the Marlin dir needs to be copied to the arduino environment. copy Marlin\sanguino \hardware\Sanguino

Install Ultimaker's RepG 25 build For SD handling and as better substitute (apart from stl manipulation) download the very nice Kliment's printrun/pronterface

Copy the Ultimaker Marlin firmware (Use the download button)

Start the arduino IDE. Select Tools -> Board -> Arduino Mega 2560 or your microcontroller Select the correct serial port in Tools ->Serial Port Open Marlin.pde

Click the Verify/Compile button

Click the Upload button If all goes well the firmware is uploading

Start Ultimaker's Custom RepG 25 Make sure Show Experimental Profiles is enabled in Preferences Select Sprinter as the Driver

Press the Connect button.

Bug reports

KNOWN ISSUES: RepG will display: Unknown: marlin x.y.z

For bug reporting please use the Issue tracker on github