Reference Zero Absolute/Relative - FiveCo FMod-IPAXESCTRL User Manual

7. Reference zero absolute/relative

FMod-IPAXESCTRL can work with the exact position coming from each
FMod-IPxxMOT, in which case we speak about an absolute zero, because
the "0" displayed on the FMod-IPAXESCTRL means that the corresponding
axis POSITION register is really at position 0.
It is sometimes useful to set a new reference "0" that is not the "0" set
during the calibration (homing) of the FMod-IPxxMOT.
There are two cases in which to perform that action:
1. A new "0" is sent to the corresponding FMod-IPxxMOT POSITION
register. Absolute zero is changed, and the software minimum and
maximum limitations (INPUTMIN & INPUTMAX registers) could make
no sense because their reference "0" is changed, especially if a home
position (homing) is done at power-up.
2. FMod-IPxxMOT POSITION register is kept unchanged but an offset
value will be added locally in FMod-IPAXESCTRL.
In both cases, the value displayed and all the interactions are the same.
However, with the "0 relative reference", the inside FMod-IPxxMOT
reference will not change. That is very important when a range of suitable
positions (e.g. hardware limitation) is active.
What happens inside (when key function is pressed):
"Set position zero absolute" :
AXIS1POSITIONOFFSET = 0
"Set position zero relative" :
AXIS1POSITIONOFFSET += POSITION
FMod-IPDCMOT (Axis1)
POSITION
INPUT
FMod-IPAXESCTRL
+
-
AXIS1POSITIONOFFSET
+
FMod-IPAXESCTRL User Manual v.1.5
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Local position,
display, saves goal
position
Trackball, key
interaction, sets goal
position