If your talking about the "little" Gridseeds (335mh round ones),cause the 5mh ones are not meant for dual mining,look here:

http://zoomhash.com/pages/raspberry-pi-software-update

And here:

http://cryptomining-blog.com/1711-updated-guide-on-how-to-mine-both-btc-and-ltc-on-gridseed-5-chip-gc3355-asic/

Not sure cause I only mined alts with either Gridseeds