what dcc controller has all 28 buttons for sound?
Digitrax DCC controllers have the ability up to 30 Decoder function control and are pretty darn affordable. The MRC Prodigy Wireless, Advance and Advance Squared have 28 decoder function control but are more expensive. Which of those would be better for you can't be determined by me, that is for you to decide and I would recommend making a complete list of what you need from the controller and compare the specs of each controller to the list.
http://www.ebay.com/itm/270951786249?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649 does this one?
Are you looking for a system with individual buttons for every function? Or just the ability to control all 28 functions?
I know that my NCE Powercab can control 28 functions, just not with dedicated buttons.
so i can run dcc trains and the engine have has 28 sound functions so i want to get a DCC controller that has it all
The Prodigy Express won't control all 28 sound functions you want. I know because I have it on my model railroad and it works for me because the highest number of functions I have to control is 8. If you want to control 28 decoder functions, stay away from the Prodigy express.