Hi Boxin,

Measure (monitor) the direction signal TTL voltage from your BoB - it could be that it does not have persistent TTL levels for the direction signal output.

Tweakie.

Thanks for your help Tweakie.
I'll do it as soon as I get home.
I think we know what's going to happen. Unlike a parallel BOB, the DIR signal will not be persistent and apparently this does not affect Mach3.
What I am going to do? 

Just take it one step at a time, we will think of something 

Tweakie.

In fact, the outputs of the axes do not maintain the level 

Well, I finally used a flip-flop (555) triggered by DIR of the A and Z axes (One to turn on the laser and the other to turn it off).
I do not know if there is an easier way (tell me), but for now these axes are available and I will use them that way.

I agree, a flip-flop may be the best solution.

Tweakie.

I asked everyone and you were the only one who confirmed that the output should be persistent.
I could not think of a solution without knowing that before.
Thank you very much Tweakie!