If you read this thread carefully you may find some ideas for improving your command line, if you feel like spending some more time trying the alternate method.
FWIW you may also want to try the “fmtownshr” folder and BIOS instead of “fmtmarty”. They are essentially the same system.
Also, make sure your XML and BIOS files are from the version of MAME that matches the core you are using. BIOS files can change over time.
@haojiezhu hello thank you very much for all these precious detailed explanations !
There is one thing I don’t understand… with MAME libretro on Windows I don’t use .xml files & FM Town Marty works fine on RetroArch for Windows… are they required on Android ?
The only console I managed to boot with a .cmd file is the Game & Watch & this without using .xml files can you explain it to me ?
Moreover if I launch the BIOS (fmtmarty.zip) under Android it starts but without any game why ?
@haojiezhu OK thank you for your answer but why on Windows with core MAME libretro I don’t need hash files?! Here is the content of my .cmd file:
fmtmarty -cdrom "d:\games\marty\flashback.cue" -rp "d:\emulators\retroarch\system\mame\roms\" -skip_gameinfo
I don’t use any other settings & the game even starts in .bin / cue without .xml files ?! Why on Android I can’t apply the same command line ?
This…
and this…
Are why you don’t need XML files. They are manually doing what the XML makes automatic.
For that matter…
Would also negate the need for an XML. With the XML method you don’t need a rompath switch, or a media switch… both are handled by the XML.
In the case the XML is not used becasuse of the…
change.
I do think it is a bit unusual to have the ISO/CUE files in a different folder that the roms but that may just be my personal preference.
You do not need the -skip_gameinfo line… it is only for standalone MAME.
I really wish you could post a log so we can see what is actually happening… all this rolling the dice is getting nowhere.
One more question. Your command line does not point to the Retroarch executable… or use the -L switch to call a core. Are you using a front end?
If using cmd files, u don’t need xml files and u don’t need chds inside folders…for android I don’t use xml and I renamed my chds to match the frontends artwork names and they are all loose…all my chds are together in whatever folder I placed them in…oh yea and they certainly don’t need to be in the system folder of RetroArch…I have every rom on an hdd and using the nvidia shield
OK, but then why isn’t this working for me?! Why do I have a black screen ?! If my command line is right where is the error ?!
Ok I want to do it but I don’t know how ?! Can you tell me how to create this journal ?!
On Windows I only use .cmd files that I launch via the RetroArch interface. It works great but not on Android & I would really like to play on my mobile phone 
OK but again why my .cmd files are not starting my games on Android. You have seen the contents of my .cmd files… where is the error ?!
https://docs.libretro.com/guides/generating-retroarch-logs/
You didn’t say if you are using a front end. It is important information…it could be causing issues.
Your command line looks almost identical to the one I used to test above. Did you try changing your backslashes “\” to forward slashes “/” like I suggested? Backslashes serve a different purpose on Android/Linux.
Not sure if your getting ur stuff from homeboy in the hyperspin forumns but his version of mame is much more updated than what we can use on android…keep that in mind…if u using mame 227 for android then make sure your Softlist is from the same number…my cmd files are a bit different from yours…mine are this: fmtmarty -cdrom “my rom name and location” -ramsize 4 -ui_active As was stated above, mine is longer because I do 1 extra step…I make an ini file which is the only thing that gets placed in a specific RetroArch folder…that goes in /storage/0/RetroArch/system/mame/ini/…and the ini will be named fmtmarty.ini…the main thing in that ini is the line that says roms…I point it to the fmtmarty folder with all the chds …hope that helps
I made two short videos for you to see what exactly happens
BIOS boot only here
Start .cmd game file here
I will try to create a .log file thank you for your help
parse path failed! path=-ui_active.
-ui_active is also a standalone MAME switch, is not needed, and is last so interpreted as the path.
Just remove it from the command line.
To be clear… your command line looks correct in your log except for the last bit.
Change
fmtmarty -cdrom "/storage/emulated/0/ROMS/Marty/Flashback.cue" -rompath "/storage/emulated/0/RetroArh/system/mame/roms" -ui_active
To
fmtmarty -cdrom "/storage/emulated/0/ROMS/Marty/Flashback.cue" -rompath "/storage/emulated/0/RetroArh/system/mame/roms"
and you should be good to go… as long as your config/MAME/fmtmarty.opt has the mame_softlists_enable = "disabled" in it.
Edit. To actually get this to work I had to switch the order of the -rompath and the -cdrom targets. I also had to encapsulate the entire MAME command by adding an extra " at the end. (The beginning would also work.)
My command is…
“E:/RetroArch/retroarch.exe" -L “E:/RetroArch/cores/mame_libretro.dll” "fmtmarty -rompath “E:/Temp/fmtmarty” -cdrom “E:/Temp/fmtmarty/4d.chd”"
Here is a shot of it running in the Mega Bezel with my FM-Towns-[STD]-[Guest]-[Monitor] preset.
@Duimon thank you for your help here is the content of my .cmd file:
fmtmarty -rompath "/storage/emulated/0/RetroArh/system/mame/roms" -cdrom "/storage/emulated/0/ROMS/Marty/Flashback.cue"
As you can see I changed the order of the commands the BIOS statement is first I removed the -ui_active command & the slashes are the right way round (/)
I also disabled this option: mame_softlists_enable = "disabled"
Despite all these changes I still have a black screen… I do not know what to do ??? I would like to know why you show me the example with the Windows version of MAME libretro & not that of Android ?!
Can you do the test on your phone ? Thanks
[EDIT] the bezel is beautiful 
Because I do not have an android phone. I do have an android device in the closet I may break out. I have some concerns. Mostly that @sanchezmike01 is using the “-ui_active” switch, which shouldn’t work.
And I just wanted to show off. 
Try this. Create an fmtmarty.ini in your “Retroarch/system/mame/ini” folder.
Inside have the lines…
rompath /storage/emulated/0/RetroArh/system/mame/roms
inipath /storage/emulated/0/RetroArh/mame\ini
Then add the line…
mame_read_config = "enabled"
to your fmtmarty.opt file. If it’s still a rompath issue this should solve it. You should also be able to remove the rompath line from your command.
Please post another log with your results.
@Duimon Here are the changes I made:
-rp /storage/emulated/0/RetroArch/system/mame/roms/fmtmarty/
-cdrom /storage/emulated/0/ROMS/Marty/Flashback.chd
I created an fmtmarty.opt file which I copied into /storage/emulated/0/RetroArch/config/MAME/ here is its contents:
mame_alternate_renderer = "enabled"
mame_altres = "640x480"
mame_auto_save = "disabled"
mame_boot_from_cli = "disabled"
mame_boot_to_bios = "disabled"
mame_boot_to_osd = "disabled"
mame_buttons_profiles = "enabled"
mame_cheats_enable = "disabled"
mame_cpu_overclock = "default"
mame_lightgun_mode = "none"
mame_mame_4way_enable = "disabled"
mame_mame_paths_enable = "disabled"
mame_media_type = "cdrom"
mame_mouse_enable = "disabled"
mame_read_config = "disabled"
mame_saves = "game"
mame_softlists_auto_media = "disabled"
mame_softlists_enable = "disabled"
mame_throttle = "disabled"
mame_write_config = "disabled"
But despite all this nothing works I still have a black screen I’m going crazy !!! Why is nothing working ???
Here is the latest .log file here
[EDIT] in the fmtmarty.opt file I changed the line mame_media_type = "rom" in mame_media_type = "cdrom" I don’t know if this is a good idea ?!
@haojiezhu why did you delete your posts ??? I would like to try your method thank you !
You need mame_boot_from_cli = "enabled"
Ui_active may not be necessary for this system, but on Android it does work on the ini file or cmd file…I do it via batch file so I keep it always in there just in case…sord M5 is such a system that if u don’t have it there, u will need to press scroll lock on the keyboard beucase the tab button won’t work…also not all android keyboards have the scroll lock button…
Makes sense since there is no keyboard.
Interesting then that the first log showed an error related to it. I’m starting to wonder if something else is causing an issue, this really shouldn’t be this hard.
I just unpacked my shield (recently moved)…I have that and a ton of non arcade games working on mame for RetroArch android including systems with no xml…thats another thing…someone said to him to make sure u have an xml…no need for that with cmd files…I rename all my roms to insure a pacman from a computer system won’t load with a bezel from the arcsde rom because they have the same identical rom name…between that and ppl stealing ur work and selling it, then saying they were the master mind of it…lmao…the only roms I don’t rename are mame arcade roms…literally everything else is renamed …u may think it’s too much work but it’s done in seconds with apps and batch scripts
All that sounds very impressive. Do you know the command to boot from a floppy and then run a CD?
One thing the hash XML does is automatically take care of that sort of thing. While the command line can greatly increase the playable rom count, it can also be limiting.
That being said… I have no idea why the OP is having such a hard time getting this to run.
With enough patience I have never failed to get a non-arcade system up and running… if it will run at all.
Not at all. I have hundreds of hours into my HTPC. It only needs to be done once and you may as well do it right.
I would really appreciate your insight to the bootable floppy >>> cdrom floppy thing.