I used Robert modified firmware for this machine: [sourceforge.net]
Marlin ABL version 1.1.9 using SN04 and I changed a bit to open filament out detector,
I have not used ABL because I can't find my SN04 anymore, so just run:
1)Home X, it raises Z which I don't want, Home Y would be similar, XYZ directions are all correct
2)Home All, it gets to (61,108,1) and what I want is (0,0,1.2), Z=1.2 will leave one paper sheet gap, 1mm touchs bed has vabration sound-always there, 1.1 has minor vibration
How to resolve these? I it first time for me to use Marlin and factory f/w would be Repetier, I'm s/w engineer. Thanks for help.

Edited 5 time(s). Last edit at 12/07/2020 12:04PM by lastguy.

I update incase others need them.
I don't bother the stopped (61,108,1) as I can simply add G0 on start code.
I complete ABL using SN04, gap to bed is 2mm or less. If ABL fail in middle, it is likely to be SN04 not detected, user needs manually adjust bed.
whenever SN04 relocated, Z offset needs to be redo and store.
Here are my code:
Start G-code:
M190 S55 ; set bed temperature and wait for it to be reached
M140 S65 ; set bed temperature
M104 S210 ; set hotend temp
G28 ; home all axes,
G29 ; ABL, hotend stops at end point
G1 X0 Y0 Z30 ; help for hot end cleaning before start
M190 S65 ; wait bed temp first
M109 S210 ; wait hotend temp