playing ds games on 3ds

Is there a version of the R4 or similar that allows DS games to be played on 3DS and if so, which one is the best? I am aware there's no way of playing 3DS d/l's on 3DS yet - but would like to use some of my old DS roms on the 3DS if possible - my DS phat is very old and the screen is almost scratched beyond use

acekart 2i and supercard dstwo work on 3ds, and there is also one or two R4 variants that do.