We are beginning to experiment with the Granite and EMC to set up homing for our gantry (two motors on Y axis). We want to use the Granite hard stop feature. We will simultaneously send a Homing signal to both Y drives. We invert their search directions so they both move in the same direction (so the gantry doesn't rack). After it homes to hard stop we want to have it come off the stop a small fixed amount. Then we will have EMC do a "home to index" on one of the two joints and call that home.
This is probably going to require some significant tweaking of EMC since it would normally be controlling the motors during homing and watching ferror - and we need to make it ignore things while the Granite homes. If you have any ideas on doing that please do share!
But, the main reason for this thread is that we are having some problems with the Granite homing sequence and unless we are missing a config parameter in another section, there seems to be a bug.
If we configure everything including "Use index pulse for homing" it works fine. It hits the stop, moves off stop to index and then moves the specific offset. However, if we disable "Use index pulse for homing", the motor hits the stop and then appears to be trying to move back against the stop even further rather than moving off the stop. It doesn't matter if we try to make the Homing offset negative or positive, it wants to push back into the stop every time. We can toggle the index pulse on and off and the behavior is fully repeatable. Is this a bug?
Our settings are:
Homing torque limit: 3000
Use index pulse for homing: Disabled
Index Search direction: GREYED OUT
Home switch polarity: positive
Homing hardstop threshold: 2500
Homing offset: 10000 (or -10000, doesn't matter)
Just copying the answer also here to spread the info:
It seems that there's a typo in GDtool parameter label. The homing offset is in input step scale, not in encoder counts as labeled in GDtool 2.5.x. In other words, homing offset value is also affected by change of input scale (GDtool trajectory planner settings). For example if input scale is changed from 50:50 to 50:500, then offset should be multiplied by 10 to cancel the effect of scale change.
The typo will be fixed in the next GDtool release.