Improved xh-hk4401 docs (#550)

- Changed order so FTDI is first since this is the easier option
- Changed the circuit for the inverter to one that is easier to
  make and is safer (doesn't send 5v to RPi GPIO and prevents
  back power)
- Added table to show which uart to use based on which method
  is used
- Added connetion details to FTDI method
- Added note about checking if FTDI settings are saved

docs/xh_hk4401.md

@@ -30,40 +30,50 @@ connected to the main KVM via a micro USB cable, however this is **NOT** as USB
 The control unit communicates to the KVM using the RS-232 protocol (at 5v) not USB, and one of the following
 solutions must be used.
 
-
-### An inverter circuit
-
-For this you will need:
-
-* 2x 2n7000 MOSFETs
-* 2x 10K resistors
-* 1x USB Micro connector, or sacrificial micro USB cable
-* *Optional:* USB UART adapter
-
-<img src="xh-hk4401_circuit.jpg" />
-
-You can connect this either via a USB UART adapter, or directly to the Raspberry Pi: `GND -> Pin 6`, `TX -> Pin 8`, `RX -> Pin 10`.
-On the v3 PiKVM hat you will need to disable the UART jumpers to use the on-board UART.
-
-!!! note
-    Please search online for USB pinouts to ensure you connect it properly.
-
-
-### Inverting USB UART adapter
+### Inverting USB UART adapter (FT-232) - The easy way
 
 Some USB UART adapters have the rare feature to invert the logic level of the RX/TX signals. For example the FTDI FT232 can
 be configured via the FTDI configuration GUI to do this. With such an adapter, the circuit above is not required. All you
 need is to connect it to a micro-USB connector.
 
-In order to invert the RX/TX signals, you can use [ft_prog](https://ftdichip.com/utilities/#ft_prog) and set the following settings:
+!!! warning
+    These options will only work on UART adapters with **genuine** FTDI chips. There are a lot of cheap fakes on the
+    market that either lack this option, or will prevent you from changing the settings. To avoid getting a fake
+    ensure you always purchase from a reputable store and brand (Adafruit, Sparkfun, etc.), Amazon **is not** a
+    reputable store.
+
+In order to invert the RX/TX signals, you can use [ft_prog](https://ftdichip.com/utilities/#ft_prog) and set the 
+following settings:
 
 <img src="ft232_config.png" />
 
-!!! warning
-    These options will only be available on UART adapters with genuine FTDI chips. There are a lot of cheap fakes on the
-    market that either lack this option, or will prevent you from changing their settings. To avoid getting a fake
-    ensure you always purchase from a reputable store and brand (Adafruit, Sparkfun, etc.), Amazon **is not** a
-    reputable store.
+Once the UART is configured, please fully disconnect it and connect it back to the computer. Relaunch `ft_prog` and ensure the settings are still set. If they are not, you have a *fake* FTDI chip.
+
+Finally, you will need to connect it to the micro USB port (**This it not a normal USB micro port.**)
+like so:
+
+| Signal | Colour | FT232 Pin                                           |
+| ------ | ------ | --------------------------------------------------- |
+| Vbus   | Red    | 5v (if you want to power the KVM from the Pi's USB) |
+| D-     | White  | RX                                                  |
+| D+     | Green  | TX                                                  |
+| Gnd    | Black  | GND                                                 |
+
+
+### An inverter circuit - The cheap way
+
+For this you will need:
+
+* 1x 74HC14
+* 1x USB A socket, or sacrificial micro USB cable
+* Optional 1x Diode - If you want to power the KVM from the Raspberry Pi
+* 1x 5-pin header
+* 5x Female - Female jumper cables
+
+<img src="xh-hk4401_circuit.png" />
+
+!!! note
+    Please search online for USB pinouts to ensure you connect it properly.
 
 ## Adding UI elements to control the KVM switch
 
@@ -73,7 +83,12 @@ The UI can be updated to add buttons to switch between KVM inputs and indicators
 
 2. Enable read-write mode on the sd card via `rw`
 
-3. Edit the `/etc/kvmd/override.yaml` file and include the following. Note the assumption that you are using a USB UART present on `/dev/ttyUSB0`:
+3. Edit the `/etc/kvmd/override.yaml` file and include the following. 
+
+| Method   | Device         |
+|----------|----------------|
+| FT-232   | `/dev/ttyUSB0` |
+| Inverter | `/dev/ttyAMA0` |
 
     ```yaml
     kvmd: