Self Note for getting SD reader to work on Audi Stupid Stereo System

I wanna keep a self note but I dunno where I should write this so it might as well be here so anyone who's having the same struggle can read up.... The struggle being getting the SD card reader on the Audi stereo system to say something other than "Unreadable". By Audi stereo system I'm referring to the newer version that comes with a built-in SD card reader. (I have a 2009 A4, for ref)

For a product of 2009 this SD card reader is remarkably outdated. I've took it for granted at first and randomly popped in a 4GB SDHC filled with MP3s in subfolders only to get the "Unreadable" error. After trials and errors I found that this reader requires a tight specification on the card for it to work. So here it is:

1. The card must be 2GB or below;

2. The card must be old-style SD and not the newer SDHC;

3. The card must be formatted to the older FAT16, and not the newer FAT32 (note: if you're a Mac user you're out of luck. The only FAT format available in OS X disk utility is FAT32 (which is confusingly denoted as "FAT"). Get a SD format app or use Windows);

4. I heard brand matters but can't confirm all brands. (I CAN confirm that my Toshiba 2GB didn't work while my Sandisk 2GB did);

5. Filenames must be in English or the file won't be recognized;

6. Filenames must be shorter than a certain number of characters (which I don't know exactly, I renamed all my songs to the abcdefgh_##.mp3 formats);

7. I heard files can't be in subfolders but I also heard some had it to work even in folders (just put them all in root to be safe imo).

That's it.

Conclusion: this SD card reader thingy is a piece of junk but it still kinda beats not having it at all.