Hi,
I've been reading both the Clearpath manual and the PMDX-126 manual.
I imagine you wish to have HLFB assigned as 'In Position Range', in which case it is active when the servo is within position range
whereas the PMDX-126 would regard this state as a fault, exactly as Steve has said. A single transistor and a couple of resistors could invert the signal.
How's your electronic skills? This is certainly not hard to do but you would end up with a small piece of veroboard with the dozen or so components
on it. Perfectly doable but a bit messy.
My training/job is electronics so if you wish to do something along those lines I could help.
Another alternative is to use spare inputs. The PMDX-126 can access a second port, I believe with a PMDX-108 expansion board. While PMDX gear has an unsurpassed
reputation for functionality I find myself becoming confused while reading it all. I'm sure I would pick it up if I had the hardware in front of me and I could experiment with it.
My suggestion is however to get another BoB, probably a C10 at $23.00. There is another thread running at the moment where gaining some more inputs with an ESS is the
topic of conversation:
http://www.machsupport.com/forum/index.php/topic,37395.msg256291.html#msg256291Any of those boards, the C10 is a cost effective one, could be plugged into port3 of the ESS and you can have an extra 13 inputs and five outputs, without in any way disturbing
or restricting future expansion of the PMDX-126.
It is sheer luxury to have spare inputs without having to concern yourself with combining signals and risk one signal swamping another and all of that. You could comfortably attach each HLFB
to its own input. If you want to invert the signal you can do so programmatically within the ESS plugin which is rather more elegant than having a little homemade circuit board dangling from your BoB.
Mach could very easily monitor the inputs and react in what you deem a suitable manner. Further if you have one input for each axis you'd know which axis had faulted and could post and/or log the
error. If you had three or four axes that would still leave 9-10 inputs free available for other purposes. All that for $23.00, pretty good value addition I would have thought.
Craig