What changes to 2.8 LinuxCNC .hal file would need to be made to utilize M67/M68

What changes to 2.8 LinuxCNC .hal file would need to be made to utilize M67/M68 for J-Tech laser control. I currently have the laser functioning on spindle PWM on pin 16 and utilize M3 S50 for laser on at 50% & M5 to shut it off.. I use a router so do not use any of the spindle commands for spindle use, just laser. The M3 S## works fine for vector burning in VCarve Pro, but I would like to get to doing more raster work, and it seems like the only way to accomplish this would be switching to the M67/M68 command set.

tommylight wrote:

Here is what i have:

loadrt pwmgen output_type=0

addf pwmgen.make-pulses base-thread
addf pwmgen.update servo-thread

setp pwmgen.0.enable TRUE

net analogout motion.analog-out-00 => pwmgen.0.value
net laserpwm pwmgen.0.pwm => parport.0.pin-02-out

And here is a bit of gcode for that:

G0 X110.6756 Y100.0000
F3000.0000
G1 M67 E0 Q5.1358
 X110.2585 M67 E0 Q5.3874
 X110.1751 M67 E0 Q7.5314
 X109.9249 M67 E0 Q7.2956
 X109.6747 M67 E0 Q1.4156
 X109.1743 M67 E0 Q0.8609
 X108.8407 M67 E0 Q0.7998
 X108.3403 M67 E0 Q1.0228
 X107.8399 M67 E0 Q0.7998
 X107.5897 M67 E0 Q0.9227
 X107.4229 M67 E0 Q1.2791
 X107.2560 M67 E0 Q0.9527
 X106.9224 M67 E0 Q0.8144
 X105.6714 M67 E0 Q1.4027
 X105.4212 M67 E0 Q1.2072

Also, this makes very nice gcode from pictures:
www.scorchworks.com/Dmap2gcode/dmap2gcode.html

Is there any optimization from putting the M6x commands on the same line as the motion command? I'm asking because my CAM software can generate GCode with the Sxxxx command on the motion line or I can change to the LinuxCNC post processor and generate M106 Sxxx commands on new lines after each motion command. I am processing this GCode files to create M67/M68 commands so was wondering if there's any performance issues to consider between the two because raster engraving can create huge file sizes when the standard DPI is 254 for 0.1mm movements. A test file with a 70mm x 45mm image is over 5MB of GCode.

That comment/documentation through me off when I first read it and I kept looking for how to make standard Spindle.0.speed.out work. I was thinking that the laser needed to fire with the move because the Sxxxx was on the same line as the movement.

Then I looked at it again and realized it could be the move happens and then the fire of the laser, rinse and repeat.
That's when it dawned on me this M106 or M67/M68 could be at the end of the line or on the next line as they will happen after the move and before the next move.

I guess the whole image could be off by one pixel if the intent of the GCode was to fire and then move on the same line but the standard is to put the Sxxx command after the movement.

But I'm currently interested in processing/parsing since I have choices and until someone says either way I will just take the easier route and use the CAM setup to generate M106 commands on new lines.