1

GCode Command letter was not found.

2

GCode Command value invalid or missing.

3

Grbl '$' not recognized or supported.

4

Negative value for an expected positive value.

5

Homing fail. Homing not enabled in settings.

6

Min step pulse must be greater than 3usec.

7

EEPROM read failed. Default values used.

8

Grbl '$' command Only valid when Idle.

9

GCode commands invalid in alarm or jog state.

10

Soft limits require homing to be enabled.

11

Max characters per line exceeded. Ignored.

12

Grbl '$' setting exceeds the maximum step rate.

13

Safety door opened and door state initiated.

14

Build info or start-up line > EEPROM line length

15

Jog target exceeds machine travel, ignored.

16

Jog Cmd missing '=' or has prohibited GCode.

17

Laser mode requires PWM output.

20

Unsupported or invalid GCode command.

21

> 1 GCode command in a modal group in block.

22

Feed rate has not yet been set or is undefined.

23

GCode command requires an integer value.

24

> 1 GCode command using axis words found.

25

Repeated GCode word found in block.

26

No axis words found in command block.

27

Line number value is invalid.

28

GCode Cmd missing a required value word.

29

G59.x WCS are not supported.

30

G53 only valid with G0 and G1 motion modes.

31

Unneeded Axis words found in block.

32

G2/G3 arcs need >= 1 in-plane axis word.

33

Motion command target is invalid.

34

Arc radius value is invalid.

35

G2/G3 arcs need >= 1 in-plane offset word.

36

Unused value words found in block.

37

G43.1 offset not assigned to tool length axis.

38

Tool number greater than max value.

1

Hard limit triggered. Position Lost.

2

Soft limit alarm, position kept. Unlock is Safe.

3

Reset while in motion. Position lost.

4

Probe fail. Probe not in expected initial state.

5

Probe fail. Probe did not contact the work.

6

Homing fail. The active homing cycle was reset.

7

Homing fail. Door opened during homing cycle.

8

Homing fail. Pull off failed to clear limit switch.

9

Homing fail. Could not find limit switch.

$$

Display Grbl Settings.

$x=val

Change Grbl Setting x to val.

$#

View GCode Parameters.

$G

View GCode parser state.

$C

Toggle Check Gcode Mode

$H

Run Homing Cycle

$J=gcode

Run Jogging Motion.

$X

Kill Alarm Lock state.

$I

View Build Info

$N

View saved start up code

$Nx=line

Save Start-up GCode line (x=0 or 1) There are executed on a reset.

$RST=$

Restores the Grbl settings to defaults.

$RST=#

Erases G54-G59 WCS offsets and G28/30 positions stored in EEPROM.

$RST=*

Clear and Load all data from EEPROM.

$SLP

Enable Sleep mode.

Ctrl-x

Soft Reset

?

Status report query.

~

Cycle Start/Resume from Feed Hold, Door or Program pause.

!

Feed Hold – Stop all motion.

$0

Step pulse, microseconds

$1

Step idle delay, milliseconds

$2

Step port invert, XYZmask^*

$3

Direction port invert, XYZmask^*

The direction each axis moves.

$4

Step enable invert, (0=Disable, 1=Invert)

$5

Limit pins invert, (0=N-Open. 1=N-Close)

$6

Probe pin invert, (0=N-Open. 1=N-Close)

$10

Status report, ‘?’ status.  0=WCS position, 1=Machine position, 2= plan/buffer and WCS position, 3=plan/buffer and Machine position.

$11

Junction deviation, mm

$12

Arc tolerance, mm

$13

Report in inches, (0=mm. 1=Inches)^**

$20

Soft limits, (0=Disable. 1=Enable, Homing must be enabled)

$21

Hard limits, (0=Disable. 1=Enable)

$22

Homing cycle, (0=Disable. 1=Enable)

$23

Homing direction invert, XYZmask^* Sets which corner it homes to.

$24

Homing feed, mm/min

$25

Homing seek, mm/min

$26

Homing debounce, milliseconds

$27

Homing pull-off, mm

$30

Max spindle speed, RPM

$31

Min spindle speed, RPM

$32

Laser mode, (0=Off, 1=On)

$100

Number of X steps to move 1mm

$101

Number of Y steps to move 1mm

$102

Number of Z steps to move 1mm

$110

X Max rate, mm/min

$111

Y Max rate, mm/min

$112

Z Max rate, mm/min

$120

X Acceleration, mm/sec^2

$121

Y Acceleration, mm/sec^2

$122

Z Acceleration, mm/sec^2

$130

X Max travel, mm Only for Homing and Soft Limits.

$131

Y Max travel, mm Only for Homing and Soft Limits.

$132

Z Max travel, mm Only for Homing and Soft Limits.

F

Set Feed rate in Units/min (See G20/G21).

G0

A Rapid positioning move at the Rapid Feed Rate. In Laser mode Laser will be turned off.

G1

A Cutting move in a straight line. At the Current F rate.

G2

Cut a Clockwise arc.

G3

Cut an Anti-Clockwise arc.

G4

Pause command execution for the time in Pnnn. P specifies the time in seconds. Other systems use milliseconds as the pause time, if used unchanged this can result in VERY long pauses.

G10L2

Sets the offset for a saved origin using absolute machine coordinates.

G10L20

As G10 L2 but the XYZ parameters are offsets from the current position.

G17

Draw Arcs in the XY plane, default.

G18

Draw Arcs in the ZX plane.

G19

Draw Arcs in the YZ plane.

G20

All distances and positions are in Inches

G21

All distances and positions are in mm

G28

Go to safe position. NOTE: If you have not run a homing cycle and have set the safe position this is very ‘unsafe’ to use.

G28.1

Set Safe position using absolute machine coordinates.

G30

Go to the saved G30 position.

G30.1

Set Predefined position using absolute machine coordinates, a rapid G0 move to that position will be performed before the coordinates are saved.

G38.2

Probe towards the stock, error on a failure.

G38.3

As G38.2, no error on failure

G38.4

As G38.2 but move away, stop on a loss of contact.

G38.5

As G38.4, no error on failure.

G40

Cutter Compensation off. Grbl does not support cutter compensation.

G43.1

Dynamic Tool length offset, offsets Z end of tool position for subsequent moves.

G49

Cancel Tool length Offset.

G53

Use machine coordinates in this command.

G54

Activate the relevant saved origin.

G55-59

As G54, activates a different saved position

G61

Exact Path mode. Grbl does not support any other modes.

G80

Canned Cycle Cancel. Grbl does not support any of the canned cycle modes which this cancels so it does nothing.

G90

All distances and positions are Absolute values from the current origin.

G91

All distances and positions are Relative values from the current position.

G91.1

Sets Arc incremental position mode

G92

Sets the current coordinate point, used to set an origin point of zero, commonly known as the home position.

G92.1

Reset any G92 offsets in effect to zero and zero any saved values

G93

Inverse time motion mode.

G94

Units/min mode at the current F rate.

M0

Pause.

M1

As M0 but only pauses if an optional stop switch is on.

M2

Program End, turn off spindle/laser and stops the machine.

M3

Start spindle clockwise. In Laser mode sets Constant power.

M4

As M3, In Laser Mode sets Dynamic power.

M5

Stop the Spindle

M8

Coolant on as a flood. (Same as M7)

M9

Coolant off.

M30

Same as M2.

S

Set Spindle speed in RPM or Laser Power.

X Y Z

Distances or positions on the X Y Z axes.

I J K

Distances or positions for G2 and G3 Arcs. Correspond to the Z Y X axis respectively. These are always incremental coordinates regardless of G90/G91

L

Loop Cycle Count, supported but not used.

N

Line Number, supported but not used.

R

Arc radius for G2 and G3.

P

Multi-purpose parameter depends on command it is used in.

T

Tool selection, not used.

Alarm

Homing enabled but homing cycle not run or error has been detected such as limit switch activated. Home or unlock to resume.

Idle

Waiting for any command.

Jog

Performing jog motion, no new commands until complete, except Jog commands.

Homing

Performing a homing cycle, won’t accept new commands until complete.

Check

Check mode is enabled; all commands accepted but will only be parsed, not executed.

Cycle

Running GCode commands, all commands accepted, will go to Idle when commands are complete.

Hold

Pause is in operation, resume to continue.

Safety Door

The safety door switch has been activated, similar to a Hold but will resume on closing the door. You probably don’t have a safety door on your machine!

Sleep

Sleep command has been received and executed, sometimes used at the end of a job. Reset or power cycle to continue.