Ok, just one tip, maybe for all "serial display/TFT" or even bluetooth/EXP8266 users:
Do not use "Serial" (D0/D1) on AUX 1 if the printer is connected via USB
Alternative: Serial1 or Serial3 (Serial 2 uses the Aux4 port on Ramps so you should avoid it if in use with SD-Card, Smart LCD...)
So we have:
Mega Serial
Serial : 00 (RX) and 01 (TX) (our USB-connection!)
Serial 1: 19 (RX) and 18 (TX)
Serial 2: 17 (RX) and 16 (TX)
Serial 3: 15 (RX) and 14 (TX)
Mapping Ramps:
Serial 0: Aux 1 (USB serial conflict!)
Serial 1: Z-Min (TX) Z-Max (RX)
Serial 2: Aux 4 (Display, SD-Card...)
Serial 3: Y-Min (TX) Y-Max (RX)
In Repetier Firmware I just set in "General" --> "Bluetooth serial port" --> "Serial 1" (...or in configuration.h)
As written on the table above, I removed / remapped the Z-min (Z-max is not in use) endstop pin to somewhere else (good pins are: x-max or y-max, because they are also not in use by standard printers)
With this configuration there is no further need in pass through the USB-serial signal in the serial TFT and you'll avoid conflicts, because serial pin sharing (USB serial on the mega also uses D0/D1) is dangerous and not a good idea (Example: repetier host and the serial-tft(on Serial0) are sending data the same time ---> conflict).
