G28 - Move To Origin (Homing)

I have a question:

When I face a line of G-Code source like this:

G28 X0 Z0 Y20

G28 aka Homing

It means that:

EITHER:

1. The "zero" point (W) from now on is W(x,y,z) = (0,20,0) and the rotation sensors should be zeroed at these positions

OR

2. The "zero" point (W) remains W(x,y,z)=(0,0,0)

I would like you disambiguate it!

Thanks in advance :-)

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Ongoing project [code.google.com]

I think option 3, none of the above. In typical RepRap usage, G28 means move to the home switches and then set coordinate reference to the "home position". Home position is typically (0,0,0), but may be some other value defined in the firmware config.

RepRap behaviour is somewhat different to "standard" Gcode behaviour, [reprap.org] is a good guide, but not comprehensive. The definitive interpretation requires looking at the firmware.

According to the Gcode standard, G28 should move via the point specified, but I think all Reprap firmwares ignore that, and home according to axis letters supplied, or all axes if none supplied.

I have checked RepRap Wiki many times. I will take your advice into consideration! I am currently developing a GCode controller for Lego Mindstorms NXT making use of LeJOS NXJ API

Edited 1 time(s). Last edit at 03/12/2013 11:10AM by MaR1oC.