Lot's of new things, interesting event

I have installed a Blackbox on my Shark and it does what it should when sending it gcode via bCNC. I placed a Jtech laser on the system and installed Lightburn and have been playing with it to understand how it functions. I have found an interesting issue. If I start a ‘burn’ of a loaded picture the laser fires and does it’s thing. If I press ‘Stop’ while the burn is in progress the laser turns off, x/y stops, but z will drop, sometimes a little (couple mm) sometimes more. If I press pause then stop, this drop in the z does not happen. What’s going on? It would be nice to see all of the ‘commands’ being sent to the controller from light wave vs the ‘filtered’ information in the console.

‘Stop’ is an abort (emergency stop). Pause, then stop is treated as less extreme, but LightBurn does not send a Z command in either case.

If you enable debug logging, all data going in or out gets dumped to Documents/LightBurnLog.txt. It’s not human readable, but it’s decipherable if you forward it.

The stop basically doing an ‘emergency stop/abort’ and Z doing a ‘slide down’ kind of makes sense. Whatever is being told to grbl to do is causing a drop of signal to the steppers which is then causing the z to slide down. A reason I’m not saying a move down, if I click get position after the drop of z, it hasn’t changed. Also, after the ‘slide’ you can hear the stepper ‘engage’ just as the slide stops. On my Shark, when the steppers aren’t energized the z slides to the bed with the weight of the spindle.

I did enable the debug log, and since it had nothing I could decode I tossed it.f

With that being said, what is the stop sending/doing to grbl to do the abort? It is interesting that pause/stop doesn’t have the same effect on grbl as just stop does.

May I suggest the stop button be changed to abort? Since that is more of what is happening?

Stop sends Ctrl-X to GRBL, which is an immediate stop. Pause sends a ! to GRBL, and then if you stop later, it also sends a Ctrl-X but I suspect GRBL interprets it differently if it’s actively running.

It sounds like what’s happening is that GRBL is internally resetting something and letting go of the motor enable pins on your board momentarily.

Makes full sense, thank you. From the grbl manual, for anyone one else reading…

0x18 (ctrl-x) : Soft-Reset

  • Immediately halts and safely resets Grbl without a power-cycle.
  • Accepts and executes this command at any time.
  • If reset while in motion, Grbl will throw an alarm to indicate position may be lost from the motion halt.
  • If reset while not in motion, position is retained and re-homing is not required.
  • An input pin is available to connect a button or switch.

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