I was referring to this thread
https://forum.duet3d.com/topic/15826/behavior-of-m3-command-im-laser-mode-m452
where @dc42 said there was a request to have a laser mode available for focus. Was just wondering if it ever went anywhere.
Oh well, at least I have it working now. That was the major hurdle.

@radiomodell said in NEJE-like Laser as CNC upgrade:

@sh12 PWM Vpp is 3,3V Check the link and scroll down: http://nejetool.com/module_20w.html

Thanks @radiomodell . If you go down a little further in the notes it says this:
Is the power adjustable: PWM can be adjusted, PWM: 50KHz-20KHz / 3.3V-12V
I had even contacted the seller to verify and he assured me that it was from 3.3 to 12.

Anyway I duplicated your setup and YAY, it is working! So thanks again. Now to focus it and figure correct speed.
Do you know if the firmware was ever updated to allow the laser to be on without the G1 command first for focusing purposes? I saw a thread where David was talking about that.

@radiomodell Thanks,
Even though the specs on the laser says the pwm will work on 3.3 to 12v, I will connect it to a heater pin today and change the Q to F.

@jay_s_uk said in Can I check output of pwm channel?:

I believe duex PWM pins need to be inverted.
If you use duex.fan6 and set it to on, does it turn off?

I believe this should help you
https://forum.duet3d.com/topic/17278/neje-like-laser-as-cnc-upgrade

No, that is the problem. It will only stay on. Will not turn off or change power at all.

@jay_s_uk said in Can I check output of pwm channel?:

I believe duex PWM pins need to be inverted.
If you use duex.fan6 and set it to on, does it turn off?

I believe this should help you
https://forum.duet3d.com/topic/17278/neje-like-laser-as-cnc-upgrade

Thanks for that link. Looks exactly like what I have. I responded there as it looks like @radiomodell has it working.

@radiomodell , not to hijack this thread but I am running into the exact same thing. I have the NEJE laser module but cannot get it to be controlled via pwm. It is always at full power. Can you tell me exactly how you have it wired?
I have 12v supply going to 12v, and Gnd pins. Then I have the duex fan6 pwn pin and fan6 gnd pin going to the laser pwm and temperature (or gnd) pins.

Looks like you may be able to walk me through this if you're willing.

No one?
Nobody can give me some advice or guidance?

I am trying to get my laser operational. I have read everything I can find on setting up a laser. Much of it is old but I think I have it set up correctly. However I cannot get the pwm function to work. If I try to use duex.pwm2 to control it (using pwm and gnd pins) I get nothing. If I use duex.fan6 to try to control it, it is on full power and won't adjust.
I don't know if I am getting the correct signal from the pwm.

What I have:
Duet2 wifi
Duex5
RRF 3.1.1
Laser module:
http://wiki.nejetool.com/doku.php?id=laser_module_308020w

Here is my config.g

; Configuration file for Duet WiFi (firmware version 3)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v3.1.3 on Mon Jun 15 2020 11:14:50 GMT-0600 (Mountain Daylight Time)

; General preferences
G90 ; send absolute coordinates...
M83 ; ...but relative extruder moves
M550 P"BLV Cube" ; set printer name
M669 K1 ; select CoreXY mode

; Network
M552 S1 ; enable network
M586 P0 S1 ; enable HTTP
M586 P1 S0 ; disable FTP
M586 P2 S0 ; disable Telnet

; Drives
M569 P0 S0 ; physical drive 0 goes backwords - X
M569 P1 S0 ; physical drive 1 goes backwards - Y
M569 P2 S0 ; physical drive 2 goes backwards - Z right side
M569 P3 S1 ; physical drive 3 goes forwards - Exturder
M569 P4 S0 ; physical drive 4 goes backward - Z left side
M569 P5 R-1 ; disable error warnings on driver 5
M584 X0 Y1 Z2:4 E3 ;two Z Motors connected to driver outputs Z and E1
M671 X-20:310 Y0:0 S2 ;Leadscrew at left (connected to Z) and right connected to E1) of X axis
M350 X16 Y16 Z16 E16 I1 ; configure microstepping with interpolation
M92 X100.61 Y100.61 Z400.42 E2754.00 ; set steps per mm
M566 X500.00 Y500.00 Z100.00 E40.00 ; set maximum instantaneous speed changes (mm/min)
M203 X10000.00 Y10000.00 Z6000.00 E8000.00 ; set maximum speeds (mm/min)
M201 X800.00 Y800.00 Z30.00 E120.00 ; set accelerations (mm/s^2)
M906 X1400.00 Y1400.00 Z800.00 E500.00 I30 ; set motor currents (mA) and motor idle factor in per cent
M84 S30 ; Set idle timeout

; Axis Limits
M208 X-15 Y-15 Z0 S1 ; set axis minima to compensate for skew
M208 X300 Y340 Z300 S0 ; set axis maxima

; Endstops
M574 X1 S1 P"xstop" ; configure active-high endstop for low end on X via pin xstop
M574 Y1 S1 P"ystop" ; configure active-high endstop for low end on Y via pin ystop
M574 Z1 S2 ; configure Z-probe endstop for low end on Z

; Z-Probe
M950 S0 C"duex.pwm1" ; create servo pin 0 for BLTouch
M558 P9 C"zprobe.in" H3 F120 T4800 ; set Z probe type to bltouch and the dive height + speeds
G31 P25 X30 Y-10 Z.85 ; set Z probe trigger value, offset and trigger height
M557 X25:300 Y30:285 P4:4 ; define mesh grid
M376 H10

; Heaters
M308 S0 P"bedtemp" Y"thermistor" T100000 B4138 R4700 ; configure sensor 0 as thermistor on pin bedtemp
M950 H0 C"bedheat" T0 ; create bed heater output on bedheat and map it to sensor 0
M307 H0 A64.4 C593.3 D14.4 S1.00 V23.9 B0 ; results from PID
M140 H0 ; map heated bed to heater 0
M143 H0 S120 ; set temperature limit for heater 0 to 120C
M308 S1 P"e0temp" Y"thermistor" T100000 B4725 C7.06e-8 ; configure sensor 1 as thermistor on pin e0temp
M950 H1 C"e0heat" T1 ; create nozzle heater output on e0heat and map it to sensor 1
M307 H1 A572.7 C283.7 D6.9 S1.00 V23.5 B0 ; results from PID
M143 H1 S300 ; Set temperature limit for heater 1 to 300C

; Fans
M950 F0 C"fan0" Q500 ; create fan 0 on pin fan0 and set its frequency
M106 P0 S0 H-1 ; set fan 0 value. Thermostatic control is turned off
M950 F1 C"fan1" Q500 ; create fan 1 on pin fan1 and set its frequency
M106 P1 S1 H1 T45 ; set fan 1 value. Thermostatic control is turned on
M950 F3 C"duex.fan3" Q1000 ; create Fan 3 is connected to duex fan3 pin, PWM at 1000Hz
M106 P3 S0 H-1 ; set fan 1 value. Thermostatic control is turned off

; Fan control for MCU
M308 S3 Y"mcu-temp" A"MCU" ; configure sensor 3 as thermistor on MCU
M950 F4 C"duex.fan4" Q1000 ; create fan 4 on pin duex fan4, PWM at 1000Hz
M106 P4 H3 T30 ; set fan 4 value.
M950 F5 C"duex.fan5" Q1000 ; create fan 5 on pin duex.fan5, PWM at 1000Hz
M106 P5 H3 T40 ; set fan 5 value

; Tools
M563 P0 S"E3D_V6" D0 H1 F0 ; define tool 0
G10 P0 X0 Y0 Z0 ; set tool 0 axis offsets
G10 P0 R0 S0 ; set initial tool 0 active and standby temperatures to 0C

; Calibrated MCU temp
M912 P0 S-11

; XY scale adjustment
M579 Y1.003 ; adjust the X, Y, and Z axis scales. if it should be 100mm but it is 100.3 set Y0.997 (= 100/100.3)

; Custom settings are not defined
;M501 ; Load saved parameters from non-volatile memory

I use a macro to switch to laser mode:

; Switch to Laser control

;M452 C"duex.pwm2" R255 Q20000 ; laser uses pwm2 pin, PWM frequency 20000Hz
M452 C"duex.fan6" R255 Q20000 ; laser uses fan6 pin, PWM frequency 20000Hz

That is where I try either the fan or the pwm.

And here is a sample of an etching file:

( PicEngrave Pro 6 - 3D Laser Gcode )
( Date/Time: 10-04-2019 at 09:32:52 )
( Image File: PicLaser Grey Scale )
( Image size in mm: 33.88w x 19.91h )
( Pixel Resolution: 0.11 mm )
( Max. Cut Depth: 255 mm )
( Min. Cut Depth: 0 mm )
( 3rd Axis Safe Position: 0 mm )
( Start Position: image center )
( Horizontal Axis Offset: 150 mm )
( Vertical Axis Offset: 150 mm )
( Engraving Angle: Left 45 degrees )
( Metric Mode )
( X Axis Align = 0 )
( Y Axis Align = 0 )
( Laser Commands on Same Line )
G21
G1 X150.0 Y150.0
G1 F3000
G1 X133.06 Y140.045
M5
M3 S0.0
G1 X133.06 Y140.045
G1 X133.06 Y140.045 M3 S247
G1 X133.17 Y140.045 M3 S250
G1 X133.06 Y140.155 M3 S252
G1 X133.06 Y140.265 M3 S246
G1 X133.17 Y140.155 M3 S0
G1 X133.28 Y140.045 M3 S247
G1 X133.39 Y140.045 M3 S245
G1 X133.28 Y140.155 M3 S3
G1 X133.17 Y140.265 M3 S0
G1 X133.06 Y140.375 M3 S251
G1 X133.06 Y140.485 M3 S248
G1 X133.17 Y140.375 M3 S3
G1 X133.28 Y140.265 M3 S0
G1 X133.39 Y140.155 M3 S3
G1 X133.5 Y140.045 M3 S255
G1 X133.61 Y140.045 M3 S249
G1 X133.5 Y140.155 M3 S0
G1 X133.39 Y140.265 M3 S0
G1 X133.28 Y140.375 M3 S1
G1 X133.17 Y140.485 M3 S0