Buckwheat, how to add it to beer smith ?

How to add it: ingredients menu --> grain --> add grain.

What data to enter -- not really sure.
I found nutrition info for buckwheat groats listing 11.6% protein.
Diastatic power is probably going to be very close to zero lintner unless it is malted.
As a first guess, I'd enter in details similar to what the program uses for flaked oats, but the potential and yield may be different. You'll need to experiment and deduce based on deviations from your expected OG.

I would guess you need to crush the groats finely and do a cereal mash. This thread could help:
http://www.beersmith.com/forum/index.php?topic=207.0 EDIT: Not really.

 

Both ryane (ryanbrews.blogspot.com) and oldsock (www.themadfermentationist.com) have entries on their respective blogs about using buckwheat. Perhaps you can deduce the missing data from those.