Organize M Codes by Category

- In GCodes.md

Documentation/GCodes.md

 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
+G10 - Retract filament according to settings of M207
+G11 - Retract recover filament according to settings of M208
 G28 - Home all Axis
-G29 - Detailed Z-Probe, probes the bed at 3 points.  You must be at the home position for this to work correctly.
+G29 - Detailed Z-Probe, probes the bed at 3 or more points. The printer must be homed with G28 before G29.
 G30 - Single Z Probe, probes bed at current XY location.
 G31 - Dock Z Probe sled (if enabled)
 G32 - Undock Z Probe sled (if enabled)
 G91 - Use Relative Coordinates
 G92 - Set current position to cordinates given
 ```
-## M Codes
+## Movement M Codes
 ```
-M0   - Unconditional stop - Wait for user to press a button on the LCD (Only if ULTRA_LCD is enabled)
+M0   - Wait for user, with optional prompt message (to press the LCD button, requires ULTRA_LCD)
+       M0 Click When Ready ; show "Click When Ready" until the button is pressed.
 M1   - Same as M0
-M17  - Enable/Power all stepper motors
-M18  - Disable all stepper motors; same as M84
+M400 - Finish all moves
+M999 - Restart after being stopped by error
+```
+### SD Card M Codes
+```
 M20  - List SD card
 M21  - Init SD card
 M22  - Release SD card
        syntax "M32 /path/filename#", or "M32 S<startpos bytes> !filename#"
        Call gcode file : "M32 P !filename#" and return to caller file after finishing (similar to #include).
        The '#' is necessary when calling from within sd files, as it stops buffer prereading
-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.
-M48  - Measure Z_Probe repeatability. M48 [n # of points] [X position] [Y position] [V_erboseness #] [E_ngage Probe] [L # of legs of travel]
+M540 - Enable/Disable "Stop SD Print on Endstop Hit" (req. ABORT_ON_ENDSTOP_HIT_FEATURE_ENABLED)
+       M540 S<0|1>
+M928 - Start SD logging (M928 filename.g) - ended by M29
+```
+### Hardware Control
+```
+M42  - Change pin status via gcode: P<pin> S<value>. If P is omitted the onboard LED pin will be used.
+       M42 P9 S1 ; set PIN 9 to 1. 
 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
+M112 - Emergency stop. Requires hardware reset!!
+M226 - Wait for a pin to be in some state: P<pin number> S<pin state>
+```
+### Temperature M Codes
+```
 M104 - Set extruder target temp
 M105 - Read current temp
 M106 - Fan on
 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
        IF AUTOTEMP is enabled, S<mintemp> B<maxtemp> F<factor>. Exit autotemp by any M109 without F
-M112 - Emergency stop
+M140 - Set bed target temp
+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
+M301 - Set PID parameters P I and D
+M302 - Allow cold extrudes, or set the minimum extrude S<temperature>.
+M303 - PID relay autotune S<temperature> sets the target temperature. (default target temperature = 150C)
+M304 - Set bed PID parameters P I and D
+```
+### Message M Codes
+```
 M114 - Output current position to serial port
 M115 - Capabilities string
-M117 - display message
+M117 - Display message text on the LCD
 M119 - Output Endstop status to serial port
+```
+### Endstops M Codes
+```
 M120 - Enable endstop detection
 M121 - Disable endstop detection
+```
+### Special Features M Codes
+```
 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
-M150 - Set BlinkM Color Output R: Red<0-255> U(!): Green<0-255> B: Blue<0-255> over i2c, G for green does not work.
-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 - set filament diameter and set E axis units to cubic millimeters (use S0 to set back to millimeters).: D<millimeters>- 
+M150 - Set BlinkM Color: R<red> U<green> B<blue> via I2C. Range: 0-255
+M240 - Trigger a camera to take a photograph. (Add to your per-layer GCode.)
+M250 - Set LCD contrast: C<0-63>
+M280 - Set servo position absolute. P<servo index> S<angle or microseconds>
+M300 - Play beep sound S<frequency Hz> P<duration ms>
+M380 - Activate solenoid on active extruder
+M381 - Disable all solenoids
+M600 - Pause for filament change X<xpos> Y<ypos> Z<lift> E<initial retract> L<later retract for removal>
+```
+### Units and Measures M Codes
+```
+M82  - Set E codes absolute (default)
+M83  - Set E codes relative while in Absolute Coordinates (G90) mode
+M92  - Set axis_steps_per_unit - same syntax as G92
+M200 - Set filament diameter and set E axis units to mm^3 (use S0 to set back to mm).: D<mm>
 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: P for Printing moves, R for Retract only (no X, Y, Z) moves and T for Travel (non printing) moves (ex. M204 P800 T3000 R9000) in mm/sec^2
-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
+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 homing offset
-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/sec]
-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 - Set speed factor override percentage: S<factor in percent>
 M221 - Set extrude factor override percentage: S<factor in percent>
-M226 - Wait until the specified pin reaches the state required: P<pin number> S<pin state>
-M240 - Trigger a camera to take a photograph
-M250 - Set LCD contrast C<contrast value> (value 0..63)
-M280 - Set servo position absolute. P: servo index, S: angle or microseconds
-M300 - Play beep sound S<frequency Hz> P<duration ms>
-M301 - Set PID parameters P I and D
-M302 - Allow cold extrudes, or set the minimum extrude S<temperature>.
-M303 - PID relay autotune S<temperature> sets the target temperature. (default target temperature = 150C)
-M304 - Set bed PID parameters P I and D
-M380 - Activate solenoid on active extruder
-M381 - Disable all solenoids
-M400 - Finish all moves
-M401 - Lower z-probe if present
-M402 - Raise z-probe if present
-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
+```
+### Firmware Retraction M Codes
+```
+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/s]
+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
+```
+### Z Probe M Codes
+```
+M48  - Measure Z_Probe repeatability: P<points> X<xpos> Y<ypos> V<verbosity> E=engage L<legs of travel>
+       As with G29, the E flag causes the probe to stow after each probe.
+M401 - Lower Z-probe (if present)
+M402 - Raise Z-probe (if present)
+```
+### Filament Diameter M Codes
+```
+M404 - Set (or display) Nominal Filament Diameter in mm: [N<diameter>] (e.g., 3mm or 1.75mm)
+M405 - Turn on Filament Sensor extrusion control: [D<distance>] to set distance (in cm) from sensor to extruder
 M406 - Turn off Filament Sensor extrusion control
-M407 - Display measured filament diameter
+M407 - Display measured Filament Diameter
+```
+### EEPROM Settings M Codes
+```
 M500 - Store parameters in EEPROM
 M501 - Read parameters from EEPROM (if you need reset them after you changed them temporarily).
 M502 - Revert 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). Use S0 to leave off headings.
-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]
-M665 - Set delta configurations
-M666 - Set delta endstop adjustment
+```
+### Delta M Codes
+```
+M665 - Set Delta configurations: L<diagonal rod> R<delta radius> S<segments/s>
+M666 - Set Delta endstop adjustment: X<x-adjustment> Y<y-adjustment> Z<z-adjustment>
 M605 - Set dual x-carriage movement mode: S<mode> [ X<duplication x-offset> R<duplication temp offset> ]
+```
+### Stepper Driver M Codes
+```
+M17  - Enable/Power all stepper motors
+M18  - Disable all stepper motors. (same as M84)
 M907 - Set digital trimpot motor current using axis codes.
 M908 - Control digital trimpot directly.
 M350 - Set microstepping mode.
 M351 - Toggle MS1 MS2 pins directly.
 ```
-## SCARA-specific M-Codes - May change to suit future G-code standards
+### SCARA M-Codes
+__May change to suit future G-code standards__
 ```
 M360 - SCARA calibration: Move to cal-position ThetaA (0 deg calibration)
 M361 - SCARA calibration: Move to cal-position ThetaB (90 deg calibration - steps per degree)
 M363 - SCARA calibration: Move to cal-position PsiB (90 deg calibration - steps per degree)
 M364 - SCARA calibration: Move to cal-position PSIC (90 deg to Theta calibration position)
 M365 - SCARA calibration: Scaling factor, X, Y, Z axis
-M928 - Start SD logging (M928 filename.g) - ended by M29
-M999 - Restart after being stopped by error
 ```
 
-# Comments
+## Comments
 
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