4 days into this upgrade..lots of learning an troubleshooting…..
I ordered the wrong size NPN proximity switch. I did not realize they came in different diameters. The correct diameter is 12mm (https://www.amazon.com/gp/product/B07CWR58FF/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1). The optocoupler is not needed.
Rather than order the SKR Extension cable kit (which I just clipped the cables to use the connectors), just order some 2 and 3 PIN JST XH connectors, clip and solder the new connector on.
I added the BIGTREETECH DIRECT TFT35 E3 V3.0 Touch Screen.
Lots of aggravation with learning how to compile the firmware:
Compiling Errors "libmaple/gpio.h" - fixed thanks to this post - https://github.com/bigtreetech/BIGTREETECH-SKR-mini-E3/issues/302
Successfully created a firmware.bin that I can install.
I can now control the functions of the printer in Repetier and from the touch screen.
My next problem to sort out is the homing. Whenever I press the home on the touch screen or start a test print, it grinds up stop until I power it off.
I initially had the stop switches unplugged and the jumpers on the X and Y drivers for sensorless homing. I gave up on that and swapped the cables end out and connected them to the board.
I have gone through the firmware a few times trying to figure out what is causing it to grind on the stops and have yet to figure it out.
I've tried some of the published firmware for the SKR Mini 1.2 without any luck. The differences in the 2.1 to 2.0 appear to be minimal to me.
I hope this helps anyone trying to get where I am and maybe someone has an idea about what it takes to fix my grinding issue.