Axis Setup Step Pin Active Low

[Tobe91]

Hello,
I got a question regarding the Step Pin configuration in Axis Setup.
I have a AXBB-E and using the common 2Nm Lichuan Closed Loop with LCDA357H drivers.

I wired the Step+/- pins on the driver the following way:
Step+ on 24V
Step- is on O9 AXBB-E

Now my question:
Do I have to set the "Active low" for the Step and Dir signal in UCCNC or doesn't this matter?
Or what does the Active Low setting mean?

Cheers, Tobias

[dezsoe]

This driver needs 5V. Why don't you use the non-insulated outputs? (0V and O9..O17) Do not turn on Active low on step pins. (The active low setting reverses the high and low states.)

[Tobe91]

Sorry I meant 5V and not 24V.
Like I wrote, I'm using O9 which is a non-isolated output.

Just wanted to know, what the Active Low setting is good for.
But if it's just reversing the states, then it wouldn't matter if I tick it, because the Lichuan driver is using each rising and falling edge.

[ger21]

Some drives Step input requires either rising or falling edge, so require one or the other.
For the Dir Pin, Active Low will change the direction of travel.

[cncdrive]

Yes, it depends on how the stepper drive detects the step signal.
It can detect the rising edge of the pulses or the falling edge.
It is important to set it correctly, because if it is setup in reverse to how the stepper drives reading the signal then the reading will be made on the wrong edge of the step pulse which can cause step loss and position errors on direction changes. This is because then the direction signal will happen on the wrong edge of the step signal.

[Tobe91]

Yes, it depends on how the stepper drive detects the step signal.
It can detect the rising edge of the pulses or the falling edge.
It is important to set it correctly, because if it is setup in reverse to how the stepper drives reading the signal then the reading will be made on the wrong edge of the step pulse which can cause step loss and position errors on direction changes. This is because then the direction signal will happen on the wrong edge of the step signal.

This was exactly what I was thinking, the possibility of step loss.
But if I untick the Active Low setting, I should be safe. Nevertheless I tested it with both settings, and doesn't recognize any difference.

[cncdrive]

Lost step usually happens on direction change only if the step active edge is set incorrectly.
So, it takes time for it to add up enough to become visible especially if the g-code has not many direction changes then it might remain unrecognisable.
Also if the stepper drive reads the signal fast enough then it might not cause any problems even if it is set incorrectly.