How to add a lr or libretro core to ROTT:

firstly you require the core, which is a file with a .so extension. This goes into opt/retropie/libretrocores. in this directory you create a lr-emulator folder, and inside of this folder is where the .so file goes.  Back in opt/retropie go into the configs folder, inside of this folder you want to look for the type of system if it exists, such as dreamcast or nes, if you are adding a new system that does not exist you will need to create this folder, in this folder you will need two files, retroarch.cfg and emulators.cfg. Using Dreamcast as an example, inside of emulators config you would need this line: lr-reicast = "/opt/retropie/emulators/retroarch/bin/retroarch -L /opt/retropie/libretrocores/lr-reicast/ --config /opt/retropie/configs/dreamcast/retroarch.cfg %ROM%"

this tells it where the core is and for which system it is used. retroarch.cfg would have these lines:

# Settings made here will only override settings in the global retroarch.cfg if placed above the #include line

input_remapping_directory = "/opt/retropie/configs/dreamcast/"

# input_player1_joypad_index = "0"

video_shared_context = true

#include "/opt/retropie/configs/all/retroarch.cfg"

sometimes you can get away with only the emulator config, or not needing any special instructions inside the retroarch.cfg. Once you have placed the .so file, and once you place the cfg or both config files, you can then restart emulationstation, and your new emulator will be configured. If you are adding an entirely new system, you will also require the rom folder, and need to add the system itself into /etc/emulationstation to the es_systems.cfg file, which would look like this:





    <extension>.cdi .chd .gdi .sh .CDI .CHD .GDI .SH</extension>

    <command>/opt/retropie/supplementary/runcommand/ 0 _SYS_ dreamcast %ROM%</command>




If you are adding a system like Phillips CDI that is a part of mess or mame there will be other emulator specific instructions, for example cdi requires the cdimono1 bios in the rom folder and bios folder, and the rom folder needs to be named cdimono1. 

If using ROTT on EMMC and you wish to use the SD card for roms, the es_systems.cfg file located at /etc/emulationstation will need to be modified, the easiest way to do this is to copy it to the PC and use note++. Once copied to PC and opened inside of note ++ highlight where it says /home/tinker/RetroPie/roms and click ctrl f, and go to replace all, replace it with /media/tinker/nameofromfolderonsd

when you boot the system you will need to use sudo mount /dev/mmcblk0p1 /media/tinker. your sd will be mounted. be sure to swap the es_systems.cfg so it knows where to find the roms.

If you want the SD card to auto mount upon reboot rather than having to manually mount the card each time, do the following:

(from command line; either F4 on Tinker Board or via SSH)
1. Edit the fstab file by typing
sudo nano -Bw /etc/fstab

2. Go to the first empty line at the end of the fstab file and enter the following:
/dev/mmcblk0p1 /media/tinker auto nonempty,nofail,user,uid=tinker,gid=tinker 0 2

3. Ctrl-X to exit, type Y to save the modified buffer and enter to save back to /etc/fstab

4. Reboot your machine an et voila'!  The SD card is auto mounted with your roms ready to play.

you can also just use the fstab in the zip below. 

Overclocking is enabled in rott 1.0.8. You can check the cpu frequency with sudo cpufreq-info, 

to set the cpu frequency use sudo cpufreq-set -u and the speed, for example 2.00GHz or 2.1GHz.

you can also use sudo cpufreq -g governor (performance, ondemand).

To access additional content, connect a mouse and keyboard, press f4 to exit emulation station and return to console. type sudo systemctl start lightdm, this will open desktop.

in the core zip below you don't need the .info file, but I left  it because it has... info. you can add it into the folder with the .so and it will not cause any harm.