Update README.md

Author: Konsolkongen

README.md

@@ -1,5 +1,55 @@
 # Arduino-SNES-controller-on-GameCube
-How to modify a SNES (or similar) controller to work on GameCube using a 3.3V compatible Arduino board.
+Modify a SNES (or similar) controller to work on GameCube using an Arduino. The goal was to make a cheap alternative to the expensive Hori Gameboy controller using easily available parts.
 
+Based on the Smash Box code by SimpleControllers: https://github.com/SimpleControllers/SimpleControllersBuild-a-Box
+Requires the Nintendo library by NicoHood: https://github.com/NicoHood/Nintendo
 
+# Features
+* Switch between D-pad and analog mapping
+* Two different button layouts
+* Can save current settings to be automatically re-enabled on power on
+
+Press and hold Select, L and R together with the button of choice for about one second to set the current mode. D-pad assignment and button layouts can be set individually.
 ![SNES controller](/SNES_controller.gif)
+
+The regular button layout matches the buttons on the SNES controller. The alternate button layout tries to mimic the layout of a GameCube controller which might work better for Gameboy Advance games as it should be easier to jump while running in Super Mario using this layout.
+
+Controller buttons | Regular layout | Alternate layout
+------------ | ------------- | -------------
+A | A | X
+B | B | A
+X | X | Y
+Y | Y | B
+
+# Required components
+* Controller to sacrifice
+* A compatible Arduino board @16MHz, I use an Arduino Pro Mini (must be powered by 3.3V!)
+* GameCube controller extension cord
+
+To my knowledge no 3.3V 16Mhz Arduino board exist, but the ATmega328p on a 5V 16Mhz Arduino Pro Mini can run at 3.3V. Though this is not advised to do so, I personally haven't had any issue doing so, but please keep this in mind. Additional information can be found in the microcontroller datasheet:
+http://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-7810-Automotive-Microcontrollers-ATmega328P_Datasheet.pdf
+
+# How to build (will be improved eventually)
+* Flash the code to the Arduino. An external programmer like the USBtinyISP works great.
+* Remove all components on the controller PCB and solder in the Arduino to the pads where the controller IC used to be.
+* Wire up 3.3V, GND and Data from the extension cord. DO NOT USE 5V!
+
+Arduino Pro Mini pinout:
+
+Arduino pin | Function/physical button
+------------ | -------------
+VCC | 3.3V
+GND | GND
+17 | Data
+3 | X
+4 | A
+5 | B
+6 | Y
+7 | Start
+8 | Select (Z)
+0 | L
+2 | R
+1 | Up
+9 | Right
+10 | Left
+14 | Down