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.
 
+### Inverting USB UART adapter (FT-232) - The easy way
 
-### An inverter circuit
+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.
 
-For this you will need:
+!!! 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.
 
-* 2x 2n7000 MOSFETs
-* 2x 10K resistors
-* 1x USB Micro connector, or sacrificial micro USB cable
-* *Optional:* USB UART adapter
+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="xh-hk4401_circuit.jpg" />
+<img src="ft232_config.png" />
 
-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.
+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.
 
-!!! note
-    Please search online for USB pinouts to ensure you connect it properly.
+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                                                 |
 
-### Inverting USB UART adapter
 
-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.
+### An inverter circuit - The cheap way
 
-In order to invert the RX/TX signals, you can use [ft_prog](https://ftdichip.com/utilities/#ft_prog) and set the following settings:
+For this you will need:
 
-<img src="ft232_config.png" />
+* 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
 
-!!! 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.
+<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: