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Current Status: Bug Fixing

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What bugs are we working on:
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IRC channel on freenode: #marlin-firmware

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(baaaah, #marlin was taken)

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Developer Notes
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- There are now 2 branches: The __development__ branch is where new features and code changes will be sorted out. This branch may have untested code in it, so please let us know if you find any bugs. When the __development__ branch has reached a state where it is stable, it will be moved to the __stable__ branch.

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- We are doing a kind of cleanup in the list of Issues and Pull Requests, the aim is to get to a state where we can certify the code as stable. To get the code tested as widely as possible we require several volunteers with a wide variety of hardware configurations willing to test the firmware and help us to certify it as stable. If you want to help out testing go to this issue and let us know:

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- Before you submit any pull request, we ask that you _PLEASE_ test your code before submission, even if the change seems innocuous. When creating the pull request, please include the hardware you used for testing and a short synopsis of your testing procedure. Untested pull requests are less likely to be merged, as even slight changes create the risk of breaking the main branch.

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- If you have a fix don't open an issue telling about it, but test the code and submit a pull request. Use the __development__ branch when you submit.
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Marlin 3D Printer Firmware
[![Coverity Scan Build Status](](
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[![Travis Build Status](](

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Marlin has a GPL license because I believe in open development.
Please do not use this code in products (3D printers, CNC etc) that are closed source or are crippled by a patent.
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Quick Information
This RepRap firmware is a mashup between <a href="">Sprinter</a>, <a href="">grbl</a> and many original parts.

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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...
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*   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
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    For more info see:
*   Full endstop support
*   SD Card support
*   SD Card folders (works in pronterface)
*   SD Card autostart support
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*   LCD support (ideally 20x4)
*   LCD menu system for autonomous SD card printing, controlled by an click-encoder.
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*   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.
*   PID tuning
*   CoreXY kinematics (
*   Delta kinematics
*   SCARA kinematics
*   Dual X-carriage support for multiple extruder systems
*   Configurable serial port to support connection of wireless adaptors.
*   Automatic operation of extruder/cold-end cooling fans based on nozzle temperature
*   RC Servo Support, specify angle or duration for continuous rotation servos.
*   Bed Auto Leveling.
*   Support for a filament diameter sensor, which adjusts extrusion volume
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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:

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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.
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It leads to less over-deposition at corners, especially at flat angles.

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Arc support:
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Slic3r 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.
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Also, less serial communication is needed.

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

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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
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By calling M109 S<mintemp> B<maxtemp> F<factor> you enter the autotemp mode.
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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.

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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.

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LCD Menu:
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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:
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Also, with just a 20x4 or 16x2 display, useful data is shown.

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SD card folders:
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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".

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SD card folders:
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If you place a file auto[0-9].g into the root of the sd card, it will be automatically executed if you boot the printer. The same file will be executed by selecting "Autostart" from the menu.
First *0 will be performed, than *1 and so on. That way, you can heat up or even print automatically without user interaction.

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Endstop trigger reporting:
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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.

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Coding paradigm:
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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.

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

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Implemented G Codes:

*  G0  -> G1
*  G1  - Coordinated Movement X Y Z E
*  G2  - CW ARC
*  G3  - CCW ARC
*  G4  - Dwell S<seconds> or P<milliseconds>
*  G10 - retract filament according to settings of M207
*  G11 - retract recover filament according to settings of M208
*  G28 - Home all Axis
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*  G29 - Detailed Z-Probe, probes the bed at 3 points.  You must de at the home position for this to work correctly.
*  G30 - Single Z Probe, probes bed at current XY location.
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*  G31 - Dock Z Probe sled (if enabled)
*  G32 - Undock Z Probe sled (if enabled)
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*  G90 - Use Absolute Coordinates
*  G91 - Use Relative Coordinates
*  G92 - Set current position to cordinates given

M Codes
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*  M0   - Unconditional stop - Wait for user to press a button on the LCD (Only if ULTRA_LCD is enabled)
*  M1   - Same as M0
*  M17  - Enable/Power all stepper motors
*  M18  - Disable all stepper motors; same as M84
*  M20  - List SD card
*  M21  - Init SD card
*  M22  - Release SD card
*  M23  - Select SD file (M23 filename.g)
*  M24  - Start/resume SD print
*  M25  - Pause SD print
*  M26  - Set SD position in bytes (M26 S12345)
*  M27  - Report SD print status
*  M28  - Start SD write (M28 filename.g)
*  M29  - Stop SD write
*  M30  - Delete file from SD (M30 filename.g)
*  M31  - Output time since last M109 or SD card start to serial
*  M32  - Select file and start SD print (Can be used when printing from SD card)
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*  M42  - Change pin status via gcode Use M42 Px Sy to set pin x to value y, when omitting Px the onboard led will be used.
*  M80  - Turn on Power Supply
*  M81  - Turn off Power Supply
*  M82  - Set E codes absolute (default)
*  M83  - Set E codes relative while in Absolute Coordinates (G90) mode
*  M84  - Disable steppers until next move, or use S<seconds> to specify an inactivity timeout, after which the steppers will be disabled.  S0 to disable the timeout.
*  M85  - Set inactivity shutdown timer with parameter S<seconds>. To disable set zero (default)
*  M92  - Set axis_steps_per_unit - same syntax as G92
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*  M104 - Set extruder target temp
*  M105 - Read current temp
*  M106 - Fan on
*  M107 - Fan off
*  M109 - Sxxx Wait for extruder current temp to reach target temp. Waits only when heating
*         Rxxx Wait for extruder current temp to reach target temp. Waits when heating and cooling
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*  M112 - Emergency stop
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*  M114 - Output current position to serial port
*  M115 - Capabilities string
*  M117 - display message
*  M119 - Output Endstop status to serial port
*  M126 - Solenoid Air Valve Open (BariCUDA support by jmil)
*  M127 - Solenoid Air Valve Closed (BariCUDA vent to atmospheric pressure by jmil)
*  M128 - EtoP Open (BariCUDA EtoP = electricity to air pressure transducer by jmil)
*  M129 - EtoP Closed (BariCUDA EtoP = electricity to air pressure transducer by jmil)
*  M140 - Set bed target temp
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*  M190 - Sxxx Wait for bed current temp to reach target temp. Waits only when heating
*         Rxxx Wait for bed current temp to reach target temp. Waits when heating and cooling
*  M200 D<millimeters>- set filament diameter and set E axis units to cubic millimeters (use S0 to set back to millimeters).
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*  M201 - Set max acceleration in units/s^2 for print moves (M201 X1000 Y1000)
*  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
*  M205 -  advanced settings:  minimum travel speed S=while printing T=travel only,  B=minimum segment time X= maximum xy jerk, Z=maximum Z jerk, E=maximum E jerk
*  M206 - set additional homeing offset
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*  M207 - set retract length S[positive mm] F[feedrate mm/min] Z[additional zlift/hop], stays in mm regardless of M200 setting
*  M208 - set recover=unretract length S[positive mm surplus to the M207 S*] F[feedrate mm/min]
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*  M209 - S<1=true/0=false> enable automatic retract detect if the slicer did not support G10/11: every normal extrude-only move will be classified as retract depending on the direction.
*  M218 - set hotend offset (in mm): T<extruder_number> X<offset_on_X> Y<offset_on_Y>
*  M220 S<factor in percent>- set speed factor override percentage
*  M221 S<factor in percent>- set extrude factor override percentage
*  M240 - Trigger a camera to take a photograph
*  M280 - Position an RC Servo P<index> S<angle/microseconds>, ommit S to report back current angle
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*  M300 - Play beepsound S<frequency Hz> P<duration ms>
*  M301 - Set PID parameters P I and D
*  M302 - Allow cold extrudes
*  M303 - PID relay autotune S<temperature> sets the target temperature. (default target temperature = 150C)
*  M304 - Set bed PID parameters P I and D
*  M400 - Finish all moves
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*  M401 - Lower z-probe if present
*  M402 - Raise z-probe if present
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*  M404 - N<dia in mm> Enter the nominal filament width (3mm, 1.75mm ) or will display nominal filament width without parameters
*  M405 - Turn on Filament Sensor extrusion control.  Optional D<delay in cm> to set delay in centimeters between sensor and extruder
*  M406 - Turn off Filament Sensor extrusion control
*  M407 - Displays measured filament diameter
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*  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.
*  M503 - print the current settings (from memory not from eeprom)
*  M540 - Use S[0|1] to enable or disable the stop SD card print on endstop hit (requires ABORT_ON_ENDSTOP_HIT_FEATURE_ENABLED)
*  M600 - Pause for filament change X[pos] Y[pos] Z[relative lift] E[initial retract] L[later retract distance for removal]
*  M907 - Set digital trimpot motor current using axis codes.
*  M908 - Control digital trimpot directly.
*  M350 - Set microstepping mode.
*  M351 - Toggle MS1 MS2 pins directly.
*  M928 - Start SD logging (M928 filename.g) - ended by M29
*  M999 - Restart after being stopped by error
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Configuring and compilation:

Install the latest non-beta arduino software IDE/toolset
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Download the Marlin firmware
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   For the latest development, or 
   For the latest stable release
   In both cases use the "Download Zip" button on the right.

For some spec. boards a spec. dir in the ArduinoAddons directory in the Marlin dir needs to be copied to the arduino environment. <arduino home>\hardware\
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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 or .ino
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Click the Verify/Compile button

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

That's ok.  Enjoy Silky Smooth Printing.

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Instructions for configuring Bed Auto Leveling
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There are two options for this feature. You may choose to use a servo mounted on the X carriage or you may use a sled that mounts on the X axis and can be docked when not in use.
See the section for each option below for specifics about installation and configuration. Also included are instructions that apply to both options.

Instructions for Both Options

Uncomment the "ENABLE_AUTO_BED_LEVELING" define (commented by default)
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The following options define the probing positions. These are good starting values.
I recommend to keep a better clearance from borders in the first run and then make the probes as close as possible to borders:


A few more options:

* \#define XY_TRAVEL_SPEED 6000

X and Y axis travel speed between probes, in mm/min.
Bear in mind that really fast moves may render step skipping. 6000 mm/min (100mm/s) is a good value.


The Z axis is lifted when traveling to the first probe point by Z_RAISE_BEFORE_PROBING value
and then lifted when traveling from first to second and second to third point by Z_RAISE_BETWEEN_PROBINGS.
All values are in mm as usual.

Servo Option Notes
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You will probably need a swivel Z-MIN endstop in the extruder. A rc servo do a great job.
Check the system working here: (Enable English subtitles)
Teasing ;-) video:

In order to get the servo working, you need to enable:

* \#define NUM_SERVOS 1 // Servo index starts with 0 for M280 command

* \#define SERVO_ENDSTOPS {-1, -1, 0} // Servo index for X, Y, Z. Disable with -1

* \#define SERVO_ENDSTOP_ANGLES {0,0, 0,0, 165,60} // X,Y,Z Axis Extend and Retract angles

The first define tells firmware how many servos you have.
The second tells what axis this servo will be attached to. In the example above, we have a servo in Z axis.
The third one tells the angle in 2 situations: Probing (165º) and resting (60º). Check this with command M280 P0 S{angle} (example: M280 P0 S60 moves the servo to 60º)
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Next you need to define the Z endstop (probe) offset from hotend.
My preferred method:

* a) Make a small mark in the bed with a marker/felt-tip pen.
* b) Place the hotend tip as *exactly* as possible on the mark, touching the bed. Raise the hotend 0.1mm (a regular paper thickness) and zero all axis (G92 X0 Y0 Z0);
* d) Raise the hotend 10mm (or more) for probe clearance, lower the Z probe (Z-Endstop) with M401 and place it just on that mark by moving X, Y and Z;
* e) Lower the Z in 0.1mm steps, with the probe always touching the mark (it may be necessary to adjust X and Y as well) until you hear the "click" meaning the mechanical endstop was trigged. You can confirm with M119;
* f) Now you have the probe in the same place as your hotend tip was before. Perform a M114 and write down the values, for example: X:24.3 Y:-31.4 Z:5.1;
* g) You can raise the z probe with M402 command;
* h) Fill the defines bellow multiplying the values by "-1" (just change the signal)


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Sled Option Notes
The sled option uses an electromagnet to attach and detach to/from the X carriage. See for more details on how to print and install this feature. It uses the same connections as the servo option.
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To use the sled option, you must define two additional things in Configuration.h:
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* \#define Z_PROBE_SLED
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Uncomment the Z_PROBE_SLED to define to enable the sled (commented out by default).
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Uncomment the SLED_DOCKING_OFFSET to set the extra distance the X axis must travel to dock the sled. This value can be found by moving the X axis to its maximum position then measure the distance to the right X end and subtract the width of the sled (23mm if you printed the sled from Thingiverse).
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Next you need to define the Z endstop (probe) offset from hotend.
My preferred method:
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* a) Home the X and Y axes.
* b) Move the X axis to about the center of the print bed. Make a mark on the print bed.
* c) Move the Y axis to the maximum position. Make another mark.
* d) Home the X axis and use a straight edge to make a line between the two points.
* e) Repeat (b)-(d) reversing the X and Y. When you are done you will have two lines on the print bed. We will use these to measure the offset for the Z probe endstop.
* f) Move the nozzle so that it is positioned on the center point of the two lines. You can use fine movement of 0.1mm to get it as close as possible. Note the position of X and Y.
* g) Zero the Z axis with the G92 Z0 command.
* h) Raise the Z axis about 20mmm.
* i) Use the G32 command to retrieve the sled.
* j) Now more the X and Y axis to the position recorded in (f).
* k) Lower the Z axis in 0.1mm steps until you hear the "click" meaning the mechanical endstop was trigged. You can confirm with the M119 command. Note the position of the Z axis.
* l) Make a mark on the print bed where the endstop lever has touched the print bed. Raise the Z-axis about 30mm to give yourself some room.
* m) Now measure the distance from the center point to the endstop impact site along the X and Y axis using the lines drawn previously.
* n) Fill in the values below. If the endstop mark is in front of the line running left-to-right, use positive values. If it is behind, use negative values. For the Z axis use the value from (k) and subtract 0.1mm.

For example, suppose you measured the endstop position and it was 20mm to the right of the line running front-to-back, 10mm toward the front of the line running left-to-right, and the value from (k) was 2.85. The values for the defines would be:

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That's it.. enjoy never having to calibrate your Z endstop neither leveling your bed by hand anymore ;-)
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Filament Sensor
Supports the use of a real time filament diameter sensor that measures the diameter of the filament going into the extruder and then adjusts the extrusion rate to compensate for filament that does not match what is defined in the g-code.  The diameter can also be displayed on the LCD screen. This potentially eliminates the need to measure filament diameter when changing spools of filament. Gcode becomes independent of the filament diameter. Can also compensate for changing diameter.

For examples of these sensors, see:,, Any sensor which produces a voltage equivalent to the diameter in mm (i.e. 1v = 1mm) can be used. This provides a very simple interface and may encourage more innovation in this area.

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4 new Mcodes are defined to set relevant parameters: M404, M405, M406, M407 - see above.

 Implements a delay buffer to handle the transit delay between where the filament is measured and when it gets to the extruder.