add card slot in an mp4
 

is it possible to add a card slot on an mp4?

If it was supposed to have one in the first place and if you got the soldering skills to do it, yes.

But if it didn't come with a card slot it's very likely that it doesn't have the required hardware either.

is there a schematic for an atj2085 chip with card slot? what mp3 player chip has card slot support?
thanks.