Inverting the Direction of a joint in Tandem Axis has no effect

Hello all,

I am setting up a XYYZ gantry machine. 5i25/single 7i76 setup driving Leadshine closed-loop stepper drivers.

I want to invert the direction of the tandem joint, in my case, that's stepgen 3, using:

• Because it's a closed-loop driver system, switching A+/A- wires will not work to invert the direction of the motor.
• The stepscale is a positive value for both joints in this tandem axis.
• There is no combination of stepscale sign or inverting stepgens 01 or 03 which result in stepgen 03 inverting its drection, even though I verify that the stepgen.03.direction.invert_output parameter is successfully registered as "true".

Any other ideas? Ini/HAL attached, thanks!

The direction can be inverted by simply putting a - in front of the SCALE in the ini file, or removing it if there is already there.

Thanks! So I tried that, that's what "POS" and "NEG" mean in the STEPSCALE fields in the chart in my first post.

For my primary joint on stepgen 01, adding a - in front of the stepscale value reverses the direction of the motor. For the secondary stepgen, it does not.

Since stepgen 3 never changes direction, I would suspect a hardware problem

Huh. I'll try hooking it up to stepgen 4 and see what happens, thanks for the idea.

Might be drive wiring also

You can test the direction inversion with a voltmeter or just a
LED and halcmd

halcmd setp hm2_5i25.0.stepgen.03.direction.invert_output true
halcmd setp hm2_5i25.0.stepgen.03.direction.invert_output false

Should toggle the output polarities of the direction 3 outputs

Bingo, thanks so much gents.

I'll buy a new 7i76, but for now moving to stepgen 4 has me up and running.

MartyJ wrote: Bingo, thanks so much gents.
I'll buy a new 7i76, but for now moving to stepgen 4 has me up and running.

Could be wiring? Wire the wrong side of the cage clamp?

In the end (hopefully) it was EMF the whole time. I was using a non-shielded ribbon cable to connect the 5i25 to 7i76 inside my controller box, and it passed nearby my toroidal power supply. Now I'm using a different cable routing and shielded cable, hopefully sorted.