Configurate Slave Axis

Pysiek wrote:

How do I slave the two motors together?

To _literally_ slave the two motors together, allocate Y-step and Y-dir to both sets of pins.

The complications arise when you want to auto-square to the limit switches, and if it is absolutely necessary to _never_ rack the gantry at all.
It then becomes really complicated if you have encoders with index, and horrible if the indexes are not aligned.
If we ever work out the perfect way to home a gantry then I think we will see it implemented as an automatic behaviour.

mwe wrote:

I too am looking for a solution to drive this two steppers on a gantry axis configuration.

Have a look in the sample configs at sim/gantry. Gantry-hs should give a better demonstration of how homing to the limit switches works.
There is also a stepper-gantry sample configuration with a parallel port setup included.
The 5axis/5axis sample configuration is also a gantry arrangement which includes a vismach simulation of the machine too.

All these examples have one thing in common, they use the non-trivial gantrykins setup which means that the machines starts up with all axes independent, and they need to be homed before you can switch to the XYZ coordinate system.
(Which you do with the $ key or from the "View" menu.)

For a simple cartesian gantry this is all a little over-complex, and one of the development branches (joints_axes4) contains a "gentrivkins" kinematics module that allows arbitrary mapping of joints to axes without having to switch between "Joint" and "World" mode.