Solve a Matrix differential equation?

GROUPS:
 I need to solve Milburn equation. But my code didn't work? what the problem ? H is a matrix in this code DSolve[{p'[t] + r*p[t] == r*MatrixExp[-I*H/r]*p[t]*MatrixExp[I*H/r], p[0] == 0}, p[t], t] 
 Michael Rogers 1 Vote Three things: The IC p[0] == 0 makes p[t] a scalar; should it be a matrix? The operator * does elementwise multiplication; you probably want matrix multiplication . (Dot). You probably need an explicit matrix for H, too.Finally, I'm not sure DSolve is even programmed to solve a properly coded matrix ODE in terms of a matrix-valued variable p. NDSolve can solve them numerically, provided the parameters H and r are explicit numerical matrices/scalars. For DSolve, you might also try an explicit symbolic matrix for p[t] like {{p11[t], p12[t]}, {p21[t], p22[t]}}.
 thx . i changed code to this (i gave to r , H their values) 
NDSolve[{p'[t] + r*p[t] == r*MatrixExp[-I*H/r].p[t].MatrixExp[I*H/r],    p[0] == H}, p[t], {t, 0, 10}] and it gave me this error "NDSolve::deqn: Equation or list of equations expected instead of True in the first argument "