Add docs for ddr unicorntail

README.md

@@ -117,6 +117,10 @@ Depending on the game, you also need the following dependencies installed:
   [Microsoft Visual C++ Redistributable Packages for Visual Studio 2013](https://www.microsoft.com/en-sg/download/details.aspx?id=40784)
 * The [DirectX 9 End-User Runtimes (June 2010)](https://www.microsoft.com/en-us/download/details.aspx?id=8109)
 
+See also
+[bemanitools-supplements](https://dev.s-ul.net/djhackers/bemanitools-supplement/-/blob/master/misc/win-runtime/README.md)
+for files.
+
 ## Development
 ### Building
 See the [development document](doc/development.md).

doc/ddrhook/README.md

@@ -47,3 +47,7 @@ IO hardware you want to use:
 game controllers
 * ddrio-mm: Support Minimaid custom interface
 * [ddrio-smx](ddrhook/ddrio-smx.md): Support for StepManiaX dance platforms
+
+## Unicorntail
+
+[Instructions how to run on Chimera PCBs](unicorntail.md).

doc/ddrhook/unicorntail.md

@@ -0,0 +1,45 @@
+# Unicorntail
+
+Unicorntail is a hook library to run the DDR games on a hybrid type of hardware referred to as a
+"Chimera" or "Unicorn". Compared to a "Dragon", which refers to the official stock hardware by
+Konami, a Chimera mixes the P3IO board from a PCB used with GF&DM V4-V8, Jubeat, Jubeat Ripples or
+Jubeat Knit with the motherboard from a GF&DM XG, XG2 or XG3 PCB, or a Reflec Beat PCB.
+
+Actual build instructions for such hardware are out of scope here.
+
+## Context
+
+Dragon PCBs are hard to come by compared to finding the parts for a Chimera PCB.
+
+A Chimera PCB however is different in many aspects to the Dragon PCB and requires the use of the
+`unicorntail.dll` hook library.
+
+The Dragon's P3IO has two serial ports that the regular P3IOs do not, and one of these serial ports
+is used to communicate with the card readers. Note that these are actual serial ports driven
+directly by the P3IO microcontroller, these are NOT just passed through to the motherboard like the
+proprietary COM1 and COM2 connectors. Unicorn Tail intercepts serial port IO commands being sent to
+the P3IO and redirects them to COM2 instead, since COM2 is unused on SD cabinets (on HD cabinets it
+connects to a second ACIO bus which drives the extra lighting glitz like the light spikes and maybe
+the LED strip).
+
+## Drivers
+
+You need the P3IO driver installed on your target system. These can be acquired from an actual stock
+HDD or grabbed from
+[bemanitools-supplements](https://dev.s-ul.net/djhackers/bemanitools-supplement/-/blob/master/gfdm/p3io/README.md).
+
+## Setup and run
+
+Edit the `gamestart.bat` file that you are using and append `unicorntail.dll` to the list of hooks,
+e.g.:
+
+```shell
+launcher.exe -H 33554432 -K unicorntail.dll arkmdxp3.dll %*
+```
+
+If you want to use any ddrhook library in addition, you have to have the hooks in the right order
+to make everything work correctly, e.g.:
+
+```shell
+launcher.exe -H 33554432 -K unicorntail.dll -K ddrhook2.dll arkmdxp3.dll %*
+```