DCC loco decoder is an electronic circuit that controls the vehicle movements, lights, sounds, and other functions. Wide choice of loco decoders is available on the market, but they are either high priced or function limited. Open source information is available on DCC protocol, so anyone can build his own decoder. During the time, some open source libraries and firmwares became available.
For the first try, I'll be using Arduino based decoder. Later I'll make the smaller all-in-one dedicated decoder board for each loco.