I’ve barely just begun to look, but was wondering where the specific code to perform the bed calibration lives? I have a Taz 6. I’m no stranger to Arduino 
I’d like to play around with it. I bet I can speed it up a lot, but there may be things in there for a reason so I thought I’d ask that as well.
Is there a reason why it raises Z axis so high after it initially touches each corner? Since the speed is slowed way down for the second probe contact, it takes a very long time so I’m not sure why it needs to raise the Z axis quite so high. Is it in case of a dual extruder where the T1 might not be level?
That is in the start gcode in Cura.
It is just G29 to do the Auto probe sequence, the height and etc is all in the firmware. 
The probing speed is the only thing in the start gcode to be changed.
Right, geez, I had wipe gcode on my brain!
Yes, I’m looking for where G29 is actually defined in the firmware. I believe I found it starting at line 2063.
http://download.lulzbot.com/TAZ/6.0/software/2016Q2/Marlin/Marlin_TAZ6_1.0.2.19/Marlin/Marlin_main.cpp
Now I just need to figure out how to compile everything to the .hex file. I’m used to working with regular Arduino.
You can still compile and upload with Arduino. It doesn’t have to be a hex file.
= Hex file - If I remember right! Been a couple weeks now since I did it for a Taz 2.