Added details for ft232 config for the xh_hk4401 KVM (#520)

docs/xh_hk4401.md

@@ -55,6 +55,15 @@ Some USB UART adapters have the rare feature to invert the logic level of the RX
 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:
+
+<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.
 
 ## Adding UI elements to control the KVM switch