Added wiring documentation for SKR Mini E3 boards (#843)

Thank you for your contribution - looks good to me

wiki/hardware-connection.md

@@ -49,6 +49,7 @@ click to enlarge
   - [RAMPS 1.4/Re-ARM board](#ramps-14re-arm-board)
   - [Smoothieboard board](#Smoothieboard-board)
   - [Weedo Tina2 board](#Weedo-Tina2-board)
+  - [SKR Mini E3 board](#SKR-Mini-E3-board)
   - [For printer boards not listed here](#For-printer-boards-not-listed-here)
 - [ESP boards](#ESP-boards)
   - [ESP-01](#ESP-01)
@@ -281,6 +282,19 @@ Note the Mega2560 is 5V powered and ESP is 3V3 powered.
 
 ---
 
+### SKR Mini E3 board
+
+This board is from Bigtreetech and went through various hardware revisions; all of them still feature a TFT pin header which is where you can tap the TX and RX needed. The wiring below is made with a 1.2 board, but the same applies for the other revisions as well; if you need the exact schematic for your mainboard version, you can check [Bigtreetech's github repository](https://github.com/bigtreetech/BIGTREETECH-SKR-mini-E3/tree/master/hardware).
+
+<img src='https://raw.githubusercontent.com/wiki/luc-github/ESP3D/images/SKR-Mini-E3/mini_12_board.jpg' width='200'>
+<img src='https://raw.githubusercontent.com/wiki/luc-github/ESP3D/images/SKR-Mini-E3/skr_mini_12_schematic.png' width='200'><br>
+
+
+You literally cannot miss it because the TFT connector is labeled on the board; you can use dupont connectors for the wiring job, no soldering skills needed as long as your ESP comes with pre soldered headers. 
+Just a heads up: the TFT connector provides 5V DC, so be sure to provide them on the correct ESP pin and, most importantly, if your ESP can work with 5 volts as input. You should also pay attention on the board orientation in the schematic, although I oriented it the same way as the actual picture on the left so it's easier for you. 
+
+---
+
 ### For printer boards not listed here
 
 Vast majority of printers have an USB port that is converted to UART before going to MCU. Many printers also have additional (unused) UART port you can use. When possible, always use the additional port for connecting ESP to printer board. When no additional UART port is available you might use the Tx and Rx lines between USB/UART converter and MCU but it's recommended to cut (in a reversible way) the line to USB/UART converter to avoid conflicts.