G-Codes are a widely used machine control language. They are human readable and editable. This page describes the RepRapFirmware supported G-codes. RepRapFirmware follows the philosophy of "G-code everywhere", in essence the users or external program's interaction with the firmware should be through G-codes. There are G-codes for all supported control and configuration inputs along with status and debugging information.

RepRapFirmware G-codes were originally based on the information from the RepRap wiki G-code page. There are some G-Codes listed on that page that are not implemented in RepRapFirmware. More details can be found on the G-Codes not implemented page.

A typical piece of G-code sent to a machine running RepRapFirmware might look like this (The meaning of these codes (and more) is explained below on this page.)

G10 P0 S195 R175
T0
G1 X100 Y100 Z0.3 F3000
G1 X100.4 Y99.3 E0.23 F600
...many 1000 more lines...

A design philosophy of RepRapFirmware is "G-code everywhere" what this means is explained in this sub section

The G-code can originate from a number of sources:

• Sent to over USB (for example from http://www.pronterface.com/)
• Sent by the Duet Web Control Web (DWC) Interface
• Sent by an external controller such as the PanelDue.

In all cases the G-Code could

• be entered by user one line at time, for example during configuration or testing
• be sent by the User Interface (Pronterface, Web Interface or PanelDue) in response to the user pressing buttons
• originate from macros that are triggered on startup, on certain events (such as error conditions), or called by the user or UI.
• be from a g-code file which are normally stored on the on-board or external SD card.

A key difference from other 3d printer firmwares is not employing a separate command set (other than G-codes) to configure the printer. To that end RepRapFirmware has a large collection of configuration g-codes that allow the behaviour of the machine to be controlled. For some examples of when these G-Codes are employed have a look at these wiki pages:

• Configuring RepRapFirmware for a Cartesian printer
• Configuring RepRapFirmware for a Delta printer
• Configuring RepRapFirmware for a CoreXY printer
• Configuring RepRapFirmware for an IDEX printer
• Configuring RepRapFirmware for a SCARA printer
• Configuring RepRapFirmware for a Polar printer
• Configuring RepRapFirmware for a Hangprinter printer
• Tuning the heater temperature control
• Setting up automatic probing of the print bed
• Using servos and controlling unused IO pins

The advantage of "G-code everywhere" is the same commands can be send from any of the G-Code sources, and originate from the user, a UI, macro or file and it will generate the same response from the firmware. This greatly improves the ease and power of firmware configuration and operation.

This section explains the elements that make up a G-Code command.

The general rule on command order in config.g is: don't try to change the parameters of anything that you haven't already created and doesn't exist by default.

For example:

• Don't refer to any axis letter or extruder number that you haven't created using M584 (except that XYZ already exist by default)
• Don't refer to any temperature sensor in M950 or M106 before you create it using M308
• Don't refer to a heater in M307, M140, M141, M143 or m563 before you create it using M950
• Don't refer to a fan in M106 before you create it using M950
• Don't refer to a tool in G10/M568 before you create it using M563

G-Code comments begin at a semicolon, and end at the end of the line:

T0 ; This is a comment
G92 E0
;So is this
G28

Alternatively, comments can be enclosed in brackets, but they must start and end on the same line:

G28 (here come the axes to be homed) X Y

Comments and white space will be ignored by RepRapFirmware when executing the G-Code

A RepRap G-Code is a list of fields that are separated by white spaces or line breaks. A field can be interpreted as a command, parameter, or for any other special purpose. It consists of one letter directly followed by a number, or can be only a stand-alone letter (Flag). The letter gives information about the meaning of the field (see the list below in this section). Numbers can be integers (128) or fractional numbers (12.42), depending on context. For example, an X coordinate can take integers (X175) or fractionals (X17.62), but selecting extruder number 2.76 would make no sense. In this description, the numbers in the fields are represented by nnn as a placeholder.

In RepRapFirmware 3.01 and later, instead of a number you may use an expression enclosed in braces, for example {2+2}. See GCode Meta Commands for details of the supported expression types.

In RepRapFirmware, some parameters can be followed by more than one number, with colon used to separate them. Typically this is used to specify extruder parameters, with one value provided per extruder. If only one value is provided where a value is needed for each extruder, then that value is applied to all extruders.

Letter	Meaning
Gnnn	Standard G-Code command, such as move to a point
Mnnn	RepRap-defined command, such as turn on a cooling fan
Tnnn	Select tool nnn. In RepRap, a tool is typically associated with a nozzle, which may be fed by one or more extruders.
Snnn	Command parameter, such as time in seconds; temperatures; voltage to send to a motor
Pnnn	Command parameter, such as time in milliseconds; proportional (Kp) in PID Tuning
Xnnn	A X coordinate, usually to move to. This can be an Integer or Fractional number.
Ynnn	A Y coordinate, usually to move to. This can be an Integer or Fractional number.
Znnn	A Z coordinate, usually to move to. This can be an Integer or Fractional number.
U,V,W	Additional axis coordinates
Innn	Parameter - X-offset in arc move (Not yet implemented in RepRapFirmware); integral (Ki) in PID Tuning; signal inversion
Jnnn	Parameter - Y-offset in arc move (Not yet implemented in RepRapFirmware)
Dnnn	Parameter - used for diameter; derivative (Kd) in PID Tuning; drive number
Hnnn	Parameter - used for heater number in PID Tuning
Fnnn	Feedrate in mm per minute. (Speed of print head movement)
Rnnn	Parameter - used for temperatures
Qnnn	Parameter - not currently used
Ennn	Length of filament to move through the extruder. This is exactly like X, Y and Z, but for the length of filament to consume. Where a tool has more than one extruder drive then Ennn:nnn:nnn etc is supported to allow for the individual morement of each to be controlled directly
Nnnn	Line number. Used to request repeat transmission in the case of communications errors. Optional
*nnn	Checksum. Used to check for communications errors. Optional

The original NIST GCode standard requires gcode interpreters to be case-insensitive, except for characters in comments. However, not all 3D printer firmwares conform to this and some recognise uppercase command letters and parameters only.

RepRapFirmware version 1.19 and later is case-insensitive, except for characters within quoted strings. RepRapFirmware version 1.18 and earlier accept only uppercase letters for command and parameter letters.

In RepRapFirmware, quoted strings are permitted anywhere a string parameter is expected. This allows file names, WiFi passwords etc. to contain spaces, semicolons and other characters that would otherwise not be permitted. Double-quote characters are used to delimit the string, and any double-quote character within the string must be repeated.

Unfortunately, many gcode sender programs convert all characters to uppercase and don't provide any means to disable this feature. Therefore, within a quoted-string, the single-quote character is used as a flag to force the following character to lowercase. If you want to include a single quote character in the string, use two single quote characters to represent one single quote character.

Example: to add SSID MYROUTER with password ABCxyz;" 123 to the WiFi network list, use command:

M587 S"MYROUTER" P"ABCxyz;"" 123"

or if you can't send lowercase characters:

M587 S"MYROUTER" P"ABC'X'Y'Z;"" 123"

This is an optional feature that is seldom used as g-code files are normally printed form the on-board SD card.

Example: N123

If present, the line number should be the first field in a line. For G-code stored in files on SD cards the line number is usually omitted.

If checking is supported, the firmware expects line numbers to increase by 1 each line, and if that doesn't happen it is flagged as an error. But you can reset the count using M110 (see below).

Example: *71

If present, the checksum should be the last field in a line, but before a comment. For G-code stored in files on SD cards the checksum is usually omitted.

If checking is supported, the RepRap firmware checks the checksum against a locally-computed value and, if they differ, requests a repeat transmission of the line of the given number.

Example: N123 [...G Code in here...] *71

The firmware checks the line number and the checksum.

You can leave both of these out - RepRap will still work, but it won't do checking. You have to have both or neither though. If only one appears, it produces an error. See this thread for an example of usage, in this case sending g-code to the PanelDue port without disabling cheksums: https://forum.duet3d.com/topic/15134/how...

The checksum "cs" for a G-Code string "cmd" (including its line number) is computed by exor-ing the bytes in the string up to and not including the * character as follows:

int cs = 0;
for(i = 0; cmd[i] != '*' && cmd[i] != NULL; i++)
 cs = cs ^ cmd[i];
cs &= 0xff; // Defensive programming...

and the value is appended as a decimal integer to the command after the * character.

In RepRapFirmware 3.01 and later, if the line begins with a recognised keyword (optionally preceded by N and a line number, and/or space or tab characters) then that whole line of GCode is interpreted as a meta-command. Recognised keywords are:

abort elif else if set var while

See GCode Meta Commands for details of these commands.

A line that does not start with one of these keywords must start with command letter G, M or T or be empty apart from white space and comments. Exception: when in CNC or Laser mode, if a line does not start with a G, M or T command but nevertheless has other fields, and the previous line that included a command was a G0, G1, G2 or G3 command, then the previous command will be repeated with values from the new fields. This is to support GCode generated for CNC machines.

RepRapFirmware allows multiple G- and M-commands to be included in a single line. Each occurrence of G or M on the line that is preceded by a space or tab character and is not inside a quoted string or a meta command starts a new command. In RRF 3.2 and later, the space or tab character is not required.

Important: a command that invokes a macro file must be the last command in that line of GCode, because any following commands on the same line will not be executed.

RepRapFirmware stores some commands in a ring buffer internally for execution. This means that there is no (appreciable) delay while a command is acknowledged and the next transmitted. In turn, this means that sequences of line segments can be plotted without a dwell between one and the next. As soon as one of these buffered commands is received it is acknowledged and stored locally. If the local buffer is full, then the acknowledgement is delayed until space for storage in the buffer is available. PC host programs rely on this for flow control when the controller electronics does not support device level flow control.

Only the G0 to G3 movement commands are buffered by RepRapFirmware. All other G, M or T commands are not buffered. When M555 P6 is used to select nanoDLP compatibility mode, no commands are buffered.

When an unbuffered command is received it is stored, but it is not acknowledged to the host until the buffer is exhausted and then the command has been executed.

System macro gcode files are expected in "0:/sys/". See M505 for how to switch between multiple configurations

User macro gcode files are expected in "0:/macros/"

Job gcode files are expected in "0:/gcodes/" or a sub directory of that.

"0:/ is root of the on board SD card in stand alone mode, or equivalent folder in SBC mode (/opt/dsf/sd/)

Long file names (e.g. longer than 8.3 format) are supported, file names with spaces are supported.

Full paths, including all directories and subdirectories are limited to 120 characters.

e.g.:

0:/gcodes/0123456789/012.gcode

counts as 30 characters

As a general rule, any G or M command can be sent at any time. This means all settings can be changed 'on the fly', i.e. while printing. This does not take into account logical considerations, or individual pre-requisites for individual commands. For example, sending new values for M566 'jerk', M201 'acceleration', or M203 'max speed' while printing is a great way to tune these values. However, while it is theoretically possible to change M563 'define a tool' while printing, it's probably not a good idea.

G0: Rapid move

G1: Controlled *(linear) move

G2: Clockwise arc move

G3: Counter-clockwise arc move

G4: Pause the machine for a period of time, in milliseconds or seconds

G10: (P parameter with R or S parameter) Sets active and standby tool temperatures

G10: (XYZUVWABC and L parameters) Sets tool offset or coordinate system origin (absolute or relative current position) for specific tool

G10: (no parameters) Retracts filament then performs any zlift/hop according to settings of M207

G11: Unretracts/recovers filament after undoing any zlift/hop according to settings of M207

G17: Sets XY as the active plane for interpreting the tool path of an arc (G2 or G3)

G18: Sets XZ as the active plane for interpreting the tool path of an arc (G2 or G3)

G19: Sets YZ as the active plane for interpreting the tool path of an arc (G2 or G3)

G20: Units from this command onwards are in inches

G21: Units from this command onwards are in millimeters

G28: Move all axes, or the specified ones, to establish a known position for them, for example by moving an axis motor until an endstop switch is triggered

G29: Uses a Z probe to measure the bed height at 4 or more points to determine its tilt and overall flatness, then enables mesh compensation so that the nozzle will remain parallel to the bed

G30: Uses a Z probe to measure bed height at a single point

G31: Sets Z probe parameters or reports status

G32: Runs macro file bed.g. This macro can be used to probe the bed and then perform auto calibration of a delta printer, perform bed levelling by moving the Z leadscrews independently, or display the manual corrections needed to the bed levelling screws.

G38.2: Probe toward workpiece, stop on contact, signal error if failure

G38.3: Probe toward workpiece, stop on contact

G38.4: Probe away from workpiece, stop on loss of contact, signal error if failure

G38.5: Probe away from workpiece, stop on loss of contact

G53: Causes all coordinates in movement commands on the remainder of the current line of GCode to be interpreted as machine coordinates, ignoring any coordinate offset of the workplace coordinate system currently in use, and also ignoring any tool offsets

G54: selects coordinate system 1

G55: selects coordinate system 2

G56: selects coordinate system 3

G57: selects coordinate system 4

G58: selects coordinate system 5

G59: selects coordinate system 6

G59.1: selects coordinate system 7

G59.2: selects coordinate system 8

G59.3: selects coordinate system 9

G60: Saves current position to slots 0, 1 or 2

G68: Rotates the coordinate system in the current plane as selected by G17, G18 or G19.

G69: Cancels any coordinate rotation that was set up by G68.

G90: All coordinates from this command onwards are absolute, relative to the origin of the machine

G91: All coordinates from this command onwards are relative to the last position.

G92: Sets position of axes by manually specifying values for the axis positions

M0: After finishing any moves left in buffer, runs either cancel.g or stop.g, then sets motors to idle and turns heaters off (unless specified not to)

M1: After finishing any moves left in buffer, runs either cancel.g or sleep.g, then turns off all motors and heaters

M3: In CNC mode turns on spindle clockwise, in Laser mode turns on laser power

M4: Turns on spindle counterclockwise

M5: In CNC mode turns off spindle, in Laser mode turns off laser power

M17: Enables all stepper motors when used without parameters, or use axes parameters to enable selectively

M18: Disables all stepper motors when used without parameters, or use axes parameters to enable selectively

M20: Lists files on the SD card. Use parameters to list files in subdirectories or on secondary SD card

M21: The specified SD card is initialized. If an SD card is loaded when the machine is switched on, this will happen by default. SD card must be initialized for the other SD functions to work.

M22: The specified SD card is released, so further (accidental) attempts to read from it are guaranteed to fail. Helpful, but not mandatory before removing the card physically.

M23: The specified file is selected ready for printing.

M24: The machine prints from the file selected with the M23 command. If the print was previously paused with M25, printing is resumed from that point.

M25: The machine pauses printing at the current position within the file.

M26: Set the file offset in bytes from the start of the SD card file selected by M23.

M27: Reports the number of bytes processed in the format bytes processed / bytes total in file

M28: The specified file is created (or overwritten if it exists) on the SD card and all subsequent commands sent to the machine are written to that file.

M29: File opened by M28 command is closed, and all subsequent commands sent to the machine are executed as normal.

M30: The specified file is deleted.

M32: The specified file is selected from the SD card and starts printing. Does the same as M23 and M24.

M36: Returns information for the specified SD card file in JSON format.

M36.1: Returns the data for a thumbnail image in a GCode file in JSON format.

M37: Enters/leaves simulation mode, or runs the specified file in simulation mode allows the electronics to compute an accurate printing time, taking into account the maximum speeds, accelerations etc. that are configured.

M38: Used to compute a hash of a file on the SD card and returns a hexadecimal string which is the SHA1 of the file.

M39: Returns information about the SD card in the specified slot in the requested format.

M42: Switches a general purpose I/O pin.

M73: Generated by some slicers to inform the firmware about the state of the print so that it can provide a better estimate of the remaining print time.

M80: Turns on the ATX power supply from standby mode to fully operational mode using the power supply control pin on the External 5V header.

M81: Turns off the ATX power supply. Counterpart to M80.

M82: Makes the extruder interpret extrusion as absolute positions.

M83: Makes the extruder interpret extrusion values as relative positions.

M84: Stop the stepper motor idle hold on all axes and extruder.

M92: Allows programming of steps per mm for motor drives.

M98: Runs the macro in the specified file.

M99: Returns from an M98 call. This is not required to return from the end of a macro and the macro naturally returns at the end of file.

M101: Same behaviour as G11 (unretract). Supported for compatibility with Simplify3D.

M102: Command ignored as it is unnecessary in RRF. Supported for compatibility with Simplify3D.

M103: Same behaviour as G10 without parameters (retract). Supported for compatibility with Simplify3D.

M104: Sets the active and standby temperature of the current or specified tool to the temperature specified, and returns control to the host immediately (i.e. before that temperature has been reached by the extruder).

M105: Reports the current and target temperatures of all active heaters.

M106: Sets fan parameters and turns them on and off.

M107: Deprecated in RepRapFirmware. Use M106 S0 instead.

M108: Breaks out of an M109 or M190 wait-for-temperature loop, continuing the print job.

M109: Sets extruder temperature and waits until within 2.5°C of target.

M110: Sets the current line number in the running Gcode file.

M111: Enables or disables debugging features, for the module number specified by the P parameter.

M112: Any moves in progress are immediately terminated, then RepRap shuts down. All motors and heaters are turned off. It can be started again by pressing the reset button or power cycling the board.

M114: Reports the X, Y, Z and E (and U, V, W, A, B, C if configured) coordinates to the host. The coordinates reported are those at the end of the last completed move.

M115: Request the Firmware Version and Capabilities of the current microcontroller.

M116: waits for all temperatures, or a specified tool or heater's temperature, and other slowly-changing variables to arrive at their set values.

M117: Causes the given message to be shown in the status line on an attached LCD or if no LCD is attached, this message will be reported on the web interface.

M118: Used to send messages to a specific target: USB, PanelDue/UART, HTTP or Telnet

M119: Returns the current state of the configured endstops.

M120: Push the state of the machine onto a stack. Called automatically when a macro file is run.

M121: Recover the last state pushed onto the stack.

M122: Reports firmware diagnostic information.

M135: Deprecated. Sets the PID to measure temperatures and calculate the power to send to the heaters

M140: Configures heaters as bed heaters and sets active and standby temperatures, turns heaters on and returns control to the host immediately.

M141: Configures heaters as chamber heaters and sets active and standby temperatures, turns heaters on and returns control to the host immediately.

M143: Configures heater maximum temperatures. When the temperature of the heater exceeds this value a heater error will be triggered.

M144: Switch the bed to its standby temperature.

M150: Sets RGB colours and brightness for Dotstar and NeoPixel LEDs.

M190: Sets the temperature of the bed and waits for the temperature to be reached.

M191: Set the temperature of the build chamber and waits for the temperature to be reached.

M200: Enables or disables volumetric extrusion per extruder, and sets the filament diameter.

M201: Sets the acceleration that axes can do in mm/second^2 for print moves.

M201.1: Set the acceleration that axes should use for special types of move that should be done using reduced acceleration, eg probing and stall homing.

M203: Sets the maximum feedrates that axes can do in mm/min.

M204: Sets the maximum acceleration for printing and/or travel moves as a whole.

M205: Sets the maximum allowable speed change (sometimes called 'jerk speed') of each motor when changing direction, in mm/sec.

M206: Deprecated. The specified values will be subtracted from the coordinates given in G0, G1 and related commands.

M207: Sets the retract length used by the G10 and G11 firmware retraction and reprime commands.

M208: The specified values set the software limits for axis travel in the specified direction. The axis limits are also the positions assumed when an endstop is triggered.

M220: Sets the speed factor override percentage.

M221: Sets extrude factor override percentage for the specified extruder.

M226: Initiates a pause in the same way as if the pause button is pressed, except that execution of all prior GCode commands in the same input stream is completed first.

M260: Send and/or receive data over the i2c bus.

M261: Deprecated. Requests data over the i2c bus.

M280: Set absolute servo position.

M290: Applies the specified additional offset to the Z coordinate for all future moves, and to apply the offset to moves that have already been queued if this can be done.

M291: Provides a more flexible alternative to M117, in particular messages that time out, messages that suspend execution until the user acknowledges them, and messages that allow the user to adjust axis positions before acknowledging them.

M292: Sent by the user interface when the user acknowledges a message that was displayed because of a blocking M291 command.

M300: Play beep sound via connected LCD, or if no LCD, via web interface.

M301: Sets Proportional (P), Integral (I) and Derivative (D) values for hot end.

M302: Disables temperature restrictions on extrusion and retraction, or sets these temperatures.

M303: This command computes the process model parameters (see M307), which are in turn used to calculate the PID constants.

M304: Sets Proportional, Integral and Derivative values for bed.

M305: Sets or reports the parameters for each temperature sensor. If using RRF 3, use M308 instead.

M307: Sets or reports the parameters for the heating process model, for each heater.

M308: Sets or reports the parameters for each connected sensor. If using RRF 2, use M305 instead.

M309: Sets or reports the feedforward PWM setting for a specified tool. Supported in RepRapFirmware v3.4 and later

M350: Sets or reports the microstepping mode for each defined axis.

M374: Saves the mesh grid parameters and height map into the specified file, or the default file heightmap.csv if no filename was specified.

M375: Loads the default grid (without parameters), or grid specified by filename. Equivalent to G29 S1.

M376: When using bed mesh compensation, specifies the height over which bed compensation tapers. Full bed compensation is applied at Z=0, tapering down to no bed compensation by the specified height.

M400: Finishes all current moves and and thus clears the buffer. Same as G4 P0.

M401: Runs macro file sys/deployprobe#.g (where # is the specified probe number) if it exists, otherwise sys/deployprobe.g if it exists.

M402: Runs macro file sys/retractprobe#.g (where # is the specified probe number) if it exists, otherwise sys/retractprobe.g if it exists.

M404: Sets filament width and nozzle diameter. Used for slicers that report filament volume, from which RRF calculates length for job status reporting.

M408: Reports system parameters in a JSON-style response. Different levels of reporting are available.

M409: Reports parameters from the Object Model of RepRapFirmware, which includes firmware configuration, Duet hardware information, and the state of the machine that RRF is controlling.

M450: Report mode the machine is running; FFF (ie 3D printer), Laser or CNC.

M451: Switches to Fused Filament Fabrication mode for filament printing.

M452: Switches to laser mode and configures laser parameters.

M453: Switches to CNC mode.

M470: Creates a new directory on the SD-Card, using the specified (or default) path.

M471: Rename or move a file or directory.

M486: Used to identify objects on the print bed and selectively cancel them if necessary.

M500: Saves current parameters to the sys/config-override.g on the SD card.

M501: Set the active parameters to those stored in sys/config-override.g on the SD card.

M502: Sets all machine parameters to the values defined in config.g, ignoring the config-override.g file so that any changes that were saved by M500 are not applied.

M503: Reports the current print settings stored in sys/config.g.

M505: Following this command, files that would normally be fetched from /sys/ (for example, homing files and system macro files in RepRapFirmware) are fetched from the specified folder instead. This command can be used to allow multiple configurations to be maintained easily.

M540: Sets the MAC address of the machine, creating a unique identifier for the Duet on the network.

M550: Sets the name of the machine. Also used for mDNS local network discovery.

M551: Sets the password for network access to the machine.

M552: Sets the IP address of the machine and enables/disables network access.

M553: Sets the network mask of the machine.

M554: Sets the Gateway IP address of the machine.

M555: Sets the firmware to a mode where its input and (especially) output behaves similar to other established firmware.

M556: This tells firmware the tangents of the angles between the axes of the machine. Obtained by printing then measuring a test part.

M557: Defines the grid used by G29 to create a bed height mesh.

M558: Defines the Z probe type and parameters of operation.

M559: Upload file, with parameters for file size and CRC-32 check. Was used in RRF 3.1 and earlier to upload files to /sys.

M560: Upload file, as M559, with terminating string. Was used in RRF 3.1 and earlier to upload files to /www.

M561: Cancels any bed-plane fitting as the result of probing (or anything else) and returns the machine to moving in the user's coordinate system.

M562: If the heater has switched off and locked because it has detected a fault, this will reset the fault condition and allow you to use the heater again.

M563: Defines a tool with the specified parameters.

M564: Allows or forbids movement of axes that have not been homed and/or limits movement to within axis boundaries.

M566: Sets the maximum allowable speed change (sometimes called 'jerk speed') of each motor when changing direction.

M567: Sets the mix ratio for a tool. When a move command contains a single E value but the current tool uses multiple extruders, each extruder will extrude the amount specified in the E parameter times the mix value for that tool.

M568: Set tool parameters to values specified. Active and standby temperatures, spindle RPM and heater state.

M569: Sets stepper driver parameters to values specified. Parameters include motor direction, enable, minimum step pulse width, interval, direction setup and hold time, and other stepper driver features.

M569.1: Set the configuration parameters of a closed loop driver. Supported for drivers attached to Duet 3 Expansion 1HCL board.

M569.2: Reads the specified register and returns the value of that register, or if a value is specified, that value is written to the specified register.

M569.3: Report a current motors encoder position to the host in units of arc degrees (1/360'ths of turns), relative to set reference position.

M569.4: Tell one or more motor drivers to apply a specified torque regardless of position.

M569.5: Collect performance data from a drive whilst in closed loop mode.

M569.6: Perform a runtime tuning manoeuvre with a closed loop drive.

M569.7: Specifies the output port that controls a brake.

M570: Sets time and temperature parameters for the detection of heater anomalies.

M571: Turns on the defined output pin whenever extrusion is being done, and turns it off when the extrusion is finished.

M572: Sets the pressure advance coefficient for the specified extruder.

M573: Gives a running average (usually taken over about five seconds) of the PWM to the specified heater.

M574: Defines the pin name, position and type of endstop or sensor that the machine has for an axis.

M575: Sets the communications parameters of the serial comms channel specified.

M576: Sets the communications parameters of the SPI channel.

M577:Wait for a specified endstop switch or input to be triggered.

M578: Fires specified inkjet head using the specified bit pattern. Not enabled in firmware by default.

M579: Scales the specified axes by the given amount, to get prints exactly the right size.

M580: Enables/disables Roland mode, which changes output to Roland Machine Language (RML).

M581: Defines parameters for external triggers.

M582: Checks state of specified trigger.

M584: Assigns stepper driver numbers to axes, and defines axes as linear or rotational.

M585: Allows the current tool's offset to be updated by driving it into a given endstop, on machines with at least one tool probe.

M586: Enables/disables network protocols (HTTP, HTTPS, FTP, Telnet, SSH) and configures parameters.

M587: Adds WiFi network SSID and password to the remembered networks list. Optionally sets IP address, gateway, netmask, DNS server and country code.

M588: Removes the specified network SSID from the remembered networks list.

M589: Configures the Duet to allow WiFi devices to connect directly, as an access point. Settings for SSID, password, IP address and optionally the WiFi channel.

M591: Configures filament sensing for the specified extruder. The sensor may be a simple filament presence detector, a device that measures movement of filament, or both.

M592: Nonlinear extrusion is a feature that compensates for the increased back pressure from the hot end as extrusion speed increases.

M593: Configures the parameters for input shaping, which is used to reduce ringing (also called ghosting).

M594: Height following mode allows the Z position of the tool to be controlled by a PID controller using feedback from a sensor. See also M951.

M595: Allows the movement queue parameters to be adjusted so that the queue can be lengthened if necessary, or kept short if a long movement queue is not needed and there are other demands on RAM.

M600: Behaves like M226 except that if macro file filament-change.g exists in /sys on the SD card, it is run in preference to pause.g.

M650: Sent by nanoDLP to execute a peel move after exposing a layer.

M651: Sent by nanoDLP to execute a peel move after exposing a layer.

M665: Set the delta calibration variables, including diagonal rod length, delta radius, printing radius, homed nozzle height and tower postion correction.

M666: Sets delta endstops and bed tilt adjustments.

M667: Deprecated. Selects CoreXY or CoreXZ mode. Use M669.

M669: Sets kinematic type (cartesian, CoreXY, CoreXZ, Delta, SCARA, Hangprinter, polar etc) and any extra kinematic parameters.

M670: Sets the port switching time advance for the specified pins.

M671: Sets the positions of 2 to 4 leadscrews or bed levelling screws used to raise/lower the bed or gantry. This allows the firmware to perform bed levelling by probing the bed and either automatically moving the leadscrews, or reporting the adjustment to be made. See the G32 command.

M672: Sends configuration data to programmable Z probes such as the Duet3D Smart Effector, for example to set the sensitivity.

M673: Aligns a plane that is mounted on a rotary axis. To make use of this code it is required to take two probe points via G30 P first.

M674: Determines the Z center point of a stash that is mounted on a rotary axis. This code is yet to be implemented.

M675: Finds the center of a cavity that can be measured using the configured axis endstop.

M701: Loads the specified material in the current active tool.

M702: Unloads the previously loaded filament from the current tool.

M703: After assigning a filament to a tool, this command may be used to run /filaments/<filament name>/config.g to set parameters like temperatures, extrusion factor, retract distance.

M750: Used as an OEM extension to enable scanner functionality in the firmware.

M751: Used to turn on communication between the 3D printing and a 3D scanner board, when attached to the USB port.

M752: Initiates a new 3D scan and uploads it to the board's SD card

M753: Instruct the attached 3D scanner to cancel the current operation.

M754: Calibrates the attached 3D scanner.

M755: Sends the ALIGN ON/OFF command the attached 3D scanner.

M756: Sends the SHUTDOWN command the attached 3D scanner.

M851: Implemented for backwards compatibility with other firmware. It sets the Z probe trigger in the same way as G31 Z-nn (note the sign reversal).

M905: Updates the machine's local date and time or reports them if no parameters are specified.

M906: Sets the peak currents to send to the stepper motors for each axis.

M911: When the supply voltage falls below the auto save threshold while a print from SD card is in progress, all heaters will be turned off, printing will be stopped immediately (probably in the middle of a move), the position saved, and the specified command string executed.

M912: Adjusts the temperature reading offset of the MCU's on-chip temperature sensor.

M913: Sets motor currents to a specified percentage of their normal values.

M914: This command is supported in the Alligator build of RepRapFirmware only.

M915: Sets the stall detection parameters and optionally the low-load current reduction parameters for TMC2660, TMC2130 or similar driver chips.

M916: If the last print was not completed and resume information has been saved (either because the print was paused or because of a power failure), then the heater temperatures, tool selection, head position, mix ratio, mesh bed compensation height map etc. are restored from the saved values and printing is resumed.

M917: Sets the percentage of the current set by M906 that is to be used when the motor is stationary but not idle, or moving very slowly.

M918: Configures RepRapFirmware for a directly-connected LCD such as a 12864 or compatible display.

M929: When event logging is enabled, important events such as power up, start/finish printing and (if possible) power down will be logged to the SD card.

M950: Used to create heaters, fans, spindles and GPIO ports, and to configure parameters.

M951: Height following mode allows the Z position of the tool to be controlled by a PID controller using feedback from a sensor. See also M594.

M952: Expansion boards without address selection switches use a default address. This command can change the address, and the default data rate.

M953: Allows the bandwidth of the CAN bus to be optimised, by increasing the data rate during transmission of CAN-FD data packets by means of the BRS (bit rate switch) feature.

M954: Used to reconfigure the board it is executed on as a CAN-connected expansion board.

M955: Configures an accelerometer with specified parameters such as pins, orientation, sample rate, resolution, SPI clock frequency.

M956: Causes the specified number of accelerometer samples to be collected and saved to a .csv file on the internal SD card.

M957: Raises an event internally, based on the given parameters, as if the event had actually occurred, and executes any related handler macro for that event.

M997: Triggers a firmware update if the necessary files are present on the SD card. Can update firmware on Duet mainboards, Duet 3 CAN-connected expansion boards, WiFi modules and PanelDue.

M998: Request a resend of the specified line of Gcode.

M999: Restarts the firmware using a software reset. Can also reboot attached SBC.

Parameters

• nnn: Tool number to select. A negative number deselects all tools.
• R1: Select the tool that was active when the print was last paused (firmware 1.20 and later)
• Pnnn: Bitmap of all the macros to be run (dc42 build 1.19 or later and ch fork 1.17b or later)
• Tool number

Example

• T0 ; select tool 0
• T1 P0 ; select tool 1 but don't run any tool change macro files
• T-1 P0 ; deselect all tools but don't run any tool change macro files
• T R1 ; select the tool that was active last time the print was paused
• T ; report the current tool number

If Tn is used to select tool n but that tool is already active, the command does nothing. Otherwise, the sequence followed is:

1. If another tool is already selected and all axes have been homed, run macro tfree#.g where # is the number of that tool. As of release 3.3, the tool change files will be actioned even if not homed, so that you can use conditional GCode to choose which commands to run.
2. If another tool is already selected, deselect it and set its heaters to their standby temperatures (as defined by the R parameter in the most recent G10/M568 command for that tool)
3. If all axes have been homed, run macro tpre#.g where # is the number of the new tool
4. Set the new tool to its operating temperatures specified by the S parameter in the most recent G10/M568 command for that tool
5. If all axes have been homed, run macro tpost#.g where # is the number of the new tool. Typically this file would contain at least a M116 command to wait for its temperatures to stabilise.
6. Apply any X, Y, Z offset for the new tool specified by G10/M568
7. Use the new tool.

Selecting a non-existent tool (49, say) just does Steps 1-2 above¹. That is to say it leaves the previous tool in its standby state. You can, of course, use the G10/M568 command beforehand to set that standby temperature to anything you like.

After a reset tools will not start heating until they are selected. You can either put them all at their standby temperature by selecting them in turn, or leave them off so they only come on if/when you first use them. The M0, M1 and M112 commands turn them all off. You can, of course, turn them all off with the M1 command, then turn some back on again. Don't forget also to turn on the heated bed (if any) if you use that trick.

Tool numbering starts at 0 by default however M563 allows the user to specify tool numbers, so with them you can have tools 17, 29 and 48 if you want. Negative numbers are not allowed. The highest Tool number that can be defined from RRF3 onwards is 49

Starting from RRF 3.3beta2 both selecting as well as deselecting with a configured spindle will stop the spindle assigned to these tools. This is in accordance to NIST GCode standard that says "after a tool change is complete the spindle is stopped".

Notes

¹ Selecting a non-existent tool also removes any X/Y/Z offset applied for the old tool.

² Under special circumstances, the execution of those macro files may not be desired. RepRapFirmware 1.19 or later supports an optional P parameter to specify which macros shall be run. If it is absent then all of the macros above will be run, else you can pass a bitmap of all the macros to be executed. The bitmap of this value consists of tfree=1, tpre=2 and tpost=4.

³ You may wish to include a move to a parking position 'within the tfreeN.g gcode macro in order to allow the new extruder to reach temperature while not in contact with the print.

⁴ Tool offsets are applied whenever there is a current tool. So they are applied in tfree.g (for the outgoing tool) and in tpost.g (for the incoming tool), but not in tpre.g (because no tool is current at that point).

Codes for print head movements follow the http://www.nist.gov/manuscript-publicati..., so RepRapFirmware should be usable for CNC milling and similar applications but be aware of the G-Codes not implemented. See also on https://en.wikipedia.org/wiki/G-code.

For more information and background, along with the master list of all RepRap G-Codes check the http://reprap.org/wiki/G-code.

For the technically minded, G-Code line endings are Unix Line Endings (\n), but will accept Windows Line Endings (\r\n), so you should not need to worry about converting between the two, but it is best practice to use Unix Line Endings where possible.

All communication is in printable ASCII characters. Messages sent back

to the host computer are terminated by a newline and look like this:

xx [line number to resend] [T:93.2 B:22.9] [C: X:9.2 Y:125.4 Z:3.7 E:1902.5] [Some debugging or other information may be here]

xx can be one of:

ok

rs

!!

ok means that no error has been detected.

rs means resend, and is followed by the line number to resend.

!! means that a hardware fault has been detected. The RepRap machine will

shut down immediately after it has sent this message.

The T: and B: values are the temperature of the currently-selected extruder

and the bed respectively, and are only sent in response to M105. If such temperatures don't exist (for example for an extruder that works at room temperature and doesn't have a sensor) then a value below absolute zero (-273^oC) is returned.

C: means that coordinates follow. Those are the X: Y: etc values. These are only

sent in response to M114 and M117.

The RepRap machine may also send lines that look like this:

// This is some debugging or other information on a line on its own. It may be sent at any time.

Such lines will always be preceded by //.

On the latest version of Pronterface and Octoprint (1.2.0+) a special comment of the form:

// action:command

is allowed to be sent from the firmware, the command can currently be pause, resume or disconnect which will execute those commands on the host.

As this is also a comment other hosts will just ignore these commands.

The most common response is simply:

ok

When the machine boots up it sends the string

start

once to the host before sending anything else. This should not be replaced or augmented

by version numbers and the like. M115 (see above) requests those.

All this means that every line sent by RepRap to the host computer except the start line has a two-character prefix (one of ok, rs, !! or //). The machine should never send a line without such a prefix.

Exceptions:

RepRapFirmware responds to some commands with a reply string in JSON format, terminated by a newline. This allows later firmware revisions to include additional information without confusing clients (e.g. PanelDue) that do not expect it, and to make responses self-describing so that the client will not be confused if responses are delayed or lost. The commands affected are:

• M20 S2
• M36
• M408

Slicers will optionally add G-Code scripts to the beginning and end of their output file to perform specified actions before and/or after a print such as z-probing the build-area, heating/cooling the bed and hotend, performing ooze free "nozzle wipe" startup routine, switching system power on/off, and even "ejecting" parts. For general information and examples (not specific to RepRapFirmware) there is more info on the https://reprap.org/wiki/Start_GCode_rout... and https://reprap.org/wiki/End_GCode_routin... pages.