Graphic LCD Overview

Graphic LCD Overview

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Graphic LCD Overview

This guide is an overview of the GLCD screen and adapter offered by Cohesion3D.

The display board is useful for seeing the status, jogging the machine, and running jobs without having your computer tethered all the time.

To connect and mount the GLCD, see the installation instructions and mounting dimensions.

Note: We frequently get asked about ordering the adapter separately. Due to a number of displays on the market causing instability and incompatibility issues, we only sell a reputable GLCD screen and our adapter together as a bundle. We are not able to sell, nor support, the adapter separately. We do this to offer the best possible user experience and appreciate your understanding.

GLCD Features

The dial knobs on the GLCD are press fit. The small white pot on the left controls the screen contrast. Turning it counter-clockwise makes the screen text brighter and clockwise makes the text darker.

The rotary encoder knob on the right navigates the menus. Turning the dial counter-clockwise goes down the menu options and clockwise to go up. Pressing the knob will drill into the currently selected option. To change the direction of the rotary knob, see the Configuration section below.

GLCD Menus

Most menus, when selected, are hardcoded to remain open for 10 seconds before the idle timeout reverts back to the main screen. The Laser menu will remain open for 60 seconds.

Main Screen:

WCS = World Coordinate System (aka Work Coordinate System)
MCS = Machine Coordinate System
mm / in = Measurements (set under “Prepare” menu below)

The above values indicate where the machine is registering the head location in the coordinate system and which increment it will be displayed in. The WCS and MCS are the same unless you have applied a different offset (G54 is typically used for CNC builds, like for laser use). You will usually only focus on the left side WCS for the X, Y, Z coordinates.

The % you see on the main screen is a feedrate override, essentially like sending an F command in GCode.

The Laser S value shows what the laser is currently firing at (see the the power parameter, S command in GCode). This can be altered under the Laser > S Value option listed below.

Menu Options

Pressing the encoder knob on the right will drill into additional menu options where you can make adjustments, as needed:

DRO – Returns to the main menu when selected

PLAY – Execute the GCode file on the SD Card

JOG – Axes functions on the GLCD will move the respective axis in the configured directions the selected amount when chosen on the menu:

  • Move 10.0
    • X, Y, Z in mm / inches
  • Move 1.0
    • X, Y, Z in mm / inches
  • Move 0.1
    • X, Y, Z in mm / inches
  • Move 0.01
    • X, Y, Z in mm / inches
  • Move 0.001
    • X, Y, Z in mm / inches
  • MPG Mode (Manual Pulse Generator)
    • 1,4,8,16,32,64
  • Feed Rates
    • X, Y, Z in Percentage %
  • GoTo Park Posn: Go to certain position previously set
  • Set Park Posn: Set certain position to move to


  • Home All Axes: Send all axes to their set home position
  • Touch Off X, Touch Off Y, Touch Off Z: Not active
  • Spindle On / Spindle Off: TBD
  • Motors Off: Disengage stepper motors
  • Coordinate System: A set of GCodes to use to offset the coordinates. Not recommended to change.
  • millimeters / inches: Select one and press enter to change the default World and Machine Coordinate System measurements. This will also apply to the movement amounts in the Jog menu.

CUSTOM – By default, this is blank on the newer stock file releases.


  • Default Acceleration: Set to 2500.00. We recommend starting at 1200 or lower.
  • X / Y / Z Steps/mm: Defaulted to 157.57 for all. See the Configuration Adjustment Guide for dialing this in.
  • Contrast: Not active. Control the contrast by the white pot in the lower left corner of the GLCD board.


  • Status: This is the LCD equivalent to testing the endstops
  • X- / Y- / Z- Probe: Test the MIN settings for limit switches
  • X+ / Y+ / Z+ Probe: Test the MAX settings for limit switches


We recommend using a potentiometer on your control panel to limit the current coming from the laser tube. For more information: PWM Control

  • Power Scale: Percentage
  • S Value: Percentage of laser power
  • Test Fire: Triggers the laser to fire at the selected level for test fires only
    • Off: Fire off
    • Low: Fire at 10%
    • 1/4: Fire at 25%
    • Half: Fire at 50%
    • 3/4: Fire at 75%
    • Full: Fire at 100%
    • Keep On: Leave laser on when menu exits

The set time out is hardcoded for the test fire on the laser screen menu in the Smoothie code. Check their repository for more information.

Run GCode Files from the GLCD

Make sure you are in Absolute Coordinates mode.

Below are the steps to run a GCode file from the GLCD screen:

  1. With the LaserBoard powered down, remove the SD card and insert it into your computer or card reader.
  2. Open or create the file design in LightBurn.
  3. On the Laser panel on the right, click the “Save GCode” button and it will open a window.
  4. Find your SD Card in your listing and save the .gcode file to the card.
  5. Safely eject the card from the computer and insert it back into the LaserBoard.
  6. With the GLCD properly connected to the controller, power on the machine.
  7. Home the machine.
  8. With the GCLD screen on, press the encoder knob on the right.
  9. Select / press the knob to navigate to Play > sd/
  10. Choose YourFileName.gc and press the knob to execute immediately.


The SD card containing the firmware and config.txt file is inserted into the controller, not the GLCD SD card slot. Power down to remove the card and make sure it is inserted back into the board before powering back up. Use a text editor, such as Sublime Text and not NotePad ++.


  • Make sure the panel.enabled is set to true if it is disabled.
  • If you want to change the rotary dial rotation, swap the panel.encoder_a_pin and panel.encoder_b_pin values.
  • The default for the panel.buzz_pin is 1.31, but can be replaced with -1 to disable beeping when selecting menu options. Make a note of the default value in the comment on the right, in case you want to enable it again later.
  • Our panel.encoder_resolution should be defaulted to 4 (not the Smoothieware default of 2).
  • Lower the panel feedrate values if you are experiencing jumping while moving the head or bed using the GLCD.

## Panel
panel.enable                                 true             # set to true to enable the panel code

# Example for reprap discount GLCD
# on glcd EXP1 is to left and EXP2 is to right, pin 1 is bottom left, pin 2 is top left etc.
# +5v is EXP1 pin 10, Gnd is EXP1 pin 9
# Encoders have two pins : A and B. Set to nc if you use no encoder. ^ defines menu move direction

panel.lcd                                     reprap_discount_glcd     #
panel.spi_channel                             0                 # spi channel to use  ; GLCD EXP1 Pins 3,5 (MOSI, SCLK)
panel.spi_cs_pin                              0.16              # spi chip select     ; GLCD EXP1 Pin 4
panel.encoder_a_pin                           3.25!^            # Encoder pin up      ; GLCD EXP2 Pin 3
panel.encoder_b_pin                           3.26!^            # Encoder pin down    ; GLCD EXP2 Pin 5
panel.click_button_pin                        1.30!^            # Click button        ; GLCD EXP1 Pin 2
panel.buzz_pin                                1.31              # Pin for buzzer      ; GLCD EXP1 Pin 1
panel.back_button_pin                         2.11!^            # back button         ; GLCD EXP2 Pin 8

panel.encoder_resolution		      4

# pins used with other panels
#panel.up_button_pin                         0.1!              # Pin for the up button, if used
#panel.down_button_pin                       0.0!              # Pin for the down button, if used
#panel.click_button_pin                      0.18!             # Pin for the click ("enter") button, if used

panel.menu_offset                            0                 # On some panels, this value must be set to 1. 
                                                               # This is a number of lines to offset the menu lines by on screen.

panel.alpha_jog_feedrate                     6000              # x jogging feedrate in mm/min
panel.beta_jog_feedrate                      6000              # y jogging feedrate in mm/min
panel.gamma_jog_feedrate                     200               # z jogging feedrate in mm/min


Encoder Knob Not Responding

If the screen is coming on, but the encoder knob on the right is not responding to rotation or presses, make sure you have both the EXP1 and EXP2 cables connected to the adapter in the correct order and that the adapter is connected to the board in the proper orientation. Trace the ribbon cables to confirm. See the GLCD Installation Instructions for more information and images.

Backlit Screen Only

For a backlit screen with no content check the following:

  • The contrast is set too high or low. Turn the pot on the left to adjust the brightness of the LCD screen.
  • The cables or SD card being inserted after powering on. Reboot after inserting the cables or card.
  • The EXP1 and EXP2 connectors being inserted backwards or not making proper contact. Review our GLCD Installation Instructions to confirm the proper orientation.

Sometimes, hitting the Reset button on the right side of the LaserBoard will allow the GLCD to boot properly.

Scrambled Screen

This scrambled screen is typically an indication of electrical interference, specifically inside the cabinet where the board and wiring is.

It is worth making sure that the machine is properly grounded.

The LPSU is a particularly large source of electrical noise / interference, so you’ll want to make sure that the 2 ribbon cables going to the GLCD are tucked away as much as possible from that and any other wires, especially the high voltage wire from the LPSU.

Some people have had good results with protecting the ribbon cables with an EMI / EMF shielded foil (or aluminum foil).

Blank Screen (No Light)

A blank screen is typically an indication of the cables being inserted backwards.

  • Trace the ribbon cables from the adapter ports to make sure EXP1 and EXP2 are going to their respective headers on the back of the display board.
  • With the power off, try swapping the connectors, matching the keyed slot orientation on the board.
  • When powering back up, the GLCD screen should turn on as soon as the LaserBoard is powered.
  • If you still are not getting power, try swapping the connectors, just to make sure.