Why RetroArch?
There are many emulators to choose from on Android. I’ve decided to focus exclusively on RetroArch, which is a frontend for the Libretro API. Many of the best emulators have been ported to Libretro these last years, so RetroArch now covers all of my needs. It also has the advantage of providing the same user interface for all the emulators and it’s open source, so I’ve been able to add some features of my own and send them upstream.

One of my favorite features of RetroArch is the ability to make the SHIELD switch between PAL and NTSC refresh rate when launching specific emulators. This allows for perfect smooth scrolling on both NTSC and PAL games.

Also if you are using a CEC remote you will be able to control the games using your remote as well as the game controller. I’m not sure exactly how the binds are on different brands of remotes, but with my Sony RM-ED060 these are the button mappings:

Arrow buttons  = Left, Right, Up, Down
OK button      = A
Options button = B
Guide button   = Start
i+ button      = Select

RetroArch is available in the Google Play Store. The official Android version of RetroArch does not yet have support for all the emulators I want to use. Therefore I’ve compiled my own version of RetroArch which includes these emulators along with some other minor tweaks. I will describe the differences below.

What’s different in my RetroArch version?
The only difference in RetroArch itself is that I’ve swapped the A and B buttons in the user interface. This now matches how you navigate in SPMC, so it seems more natural. I’ve also included all the emulator cores in the package, so you don’t have to download them like you would normally do in RetroArch. The downside is that you will not be able to upgrade to newer official versions of RetroArch directly from my version.

You can download my version of RetroArch here:
http://lindqvist.synology.me/shieldguide/retroarch-release.apk

The source code for the official cores is available here:
https://github.com/libretro

The original source code for the Frodo core is available here:
https://github.com/r-type

The source code for the my modified cores is available here:
https://github.com/diablodiab/

These are the emulators included in my RetroArch version and the differences compared to the official versions (if any):