(SOLVED) Spindle RPM - FWD/REV difference

[MX21, LCNC 2.9, Probe Basic master, 7i76ED, first time Lcnc user (been fiddling with this for a while, off and on)]

I've got a problem and I'm not sure where to start the troubleshooting.  Spindle runs at commanded RPM in forward but not reverse.

VFD (GS3) is controlled via 0-10v from 7i76ED.  Direct motor encoder feedback to VFD and to Lcnc, but Lcnc is open loop (P/I/D = 0 in .ini file)

When I command reverse, I get about 150-200RPM regardless of the desired speed.  Forward is fine from 100-8krpm, and the VFD analog offset/gain is tuned up so it's holding nicely within 10-50rpm at any speed.

VFD is reporting accurately; i.e. when I command "M3 S2000" I see ~2000rpm on both the VFD display and in halshow.

When I command "M4 S2000" I get spindle.0.out = 2000, but the VFD reports ~175rpm and the actual output in halshow is also ~175rpm.  Same response whether I use the GUI spindle FWD/REV buttons or MDI.

Spindle override responds appropriately in both GUI slider and my hal-connected panel encoder.

Direct control of the VFD via drive software and keypad works as expected in both FWD & REV.

Anyone have an idea where to start fiddling?

Thanks,
Ralph

net spindle-vel-cmd-rpm => pid.s.command

would need to be:

net spindle-vel-cmd-rpm-abs => pid.s.command

additional changes would be needed if the PID loop was used
for spindle speed feedback (it's not currently )

Well, that was easy. As usual, thank you PCW!

For my Lcnc education... if you don't mind, can you explain how the 'abs' (absolute?) changed the system response?

 

That's correct, and the 7I76E spindle analog output only works properly
with positive values

You guys are awesome.