This is not a thing to download, just a short description how to enable an UART connection between the TwoTrees Sapphire Pro (MKS Robin Nano) and TMC2209 stepper drivers.
Because it's hard to find information how to do it.
Quickest way is to use this Marlin version:https://github.com/le3tspeak/Marlin-2.0.X-Sapphire-PRO
Or this more modified version:https://github.com/Miraculix200/Marlin-SapphirePro-2209-UART/tree/SapphirePro-2209-UART-4pin
Remove all jumpers under the stepper driver
Connect RX/TX pins of the stepper driver together
Connect them to 1 free pin on the Robin Nano (e.g. PA6)
Define TMC2209 in Configuration.h
Uncomment the SERIAL_PIN lines in pins_MKS_ROBIN_NANO.h, depending on what pin(s) you used
Compile & flash
This method uses a dedicated pin for each stepper driver. It's possible to make all stepper drivers use one pin by giving each stepper driver a dedicated hardware address. But I didn't try that yet, as I only need it for one 2209 at the moment.
You don't necessarily have to solder or crimp…