Marlin has no support for dual serial.
use D0/D1 (also known as tx0/rx0)
And ensure that the usb and the screen never talk at the same tame and are same baud rate.
This is how mks tft does it
use D0/D1 (also known as tx0/rx0)
And ensure that the usb and the screen never talk at the same tame and are same baud rate.
This is how mks tft does it