I'll try...
But I think that if the signal must be persistent, there must be the problem ...
My BOB is this (due to my laptop, I can not use the parallel port for a traditional one):
https://www.aliexpress.com/item/Factory-outlets-100KHz-CNC-mach3-USB-4-Axis-Stepper-Motor-Driver-Breakout-Board-USBCNC-Smooth-Stepper/32334451366.html?spm=2114.13010608.0.0.cJRtzNMi laser:
https://www.aliexpress.com/item/Focusable-450nm-2W-Laser-Engraver-445nm-2000mW-Blue-Laser-Diode-Module-with-TTL-for-CNC-Engrave/32745647304.html?spm=2114.13010608.0.0.bcOG86The laser takes 12V from an ATX power supply.
To excite the TTL input of the laser, I am connecting a relay between + 5V and DIR- on my BOB (DIR- of Z & A axis, I have tried both).
This relay connects 5V from the same ATX power supply and sends them to the TTL input.
But beyond this connection, now I understand that the DIR signal must be persistent as you say (If I do not want to use some kind of monostable or flip-flop).
I have not measured the DIR-voltage changes, but I assume it will be almost imperceptible in my digital tester.
What I'm wondering is: is it possible that this USB BOB works differently than a traditional BOB via parallel port?
Would it affect Mach3 at all if the DIR signal is not persistent?
From what I could see when setting high values on the Z axis when the laser is turned on, it stays on during the travel of this axis. That's why there is only a flash when I want to activate it quickly.
What do you think?