  We write the master equation describing the Parrondo's games as a consistent
discretization of the Fokker--Planck equation for an overdamped Brownian
particle describing a ratchet. Our expressions, besides giving further insight
on the relation between ratchets and Parrondo's games, allow us to precisely
relate the games probabilities and the ratchet potential such that periodic
potentials correspond to fair games and winning games produce a tilted
potential.
