  We present the measurements of $D^0$ and $D^*$ in p+p and $D^0$ in Au+Au
collisions via hadronic decays $D^{0}\rightarrow K^{-}\pi^{+}$,
$D^{*+}\rightarrow D^{0}\pi^{+}\rightarrow K^{-}\pi^{+}\pi^{+}$ in mid-rapidity
$|y|<1$ at $\sqrt{s_{_{\rm NN}}}$ = 200 GeV, covering $p_T$ from 0.2 to 6
GeV/$c$ in p+p and 0.4 to 5 GeV/$c$ in Au+Au, respectively. The charm pair
production cross section per nucleon-nucleon collision at mid rapidity is
measured to be 202 $\pm$ 56 (stat.) $\pm$ 40 (sys.) $\pm$ 20 (norm.) $\mu$b in
p+p and 186 $\pm$ 22 (stat.) $\pm$ 30 (sys.) $\pm$ 18 (norm.) $\mu$b in Au+Au
minimum bias collisions. The number of binary collisions scaling of charm cross
section indicates that charm is produced via initial hard scatterings. No
suppression of $D^0$ $R_{AA}$ in Au+Au 0-80% minbias collisions is observed at
$p_T$ below 3 GeV/$c$. Blast-wave predictions with light-quark hadron
parameters are different from data, which may indicate that $D^0$ decouples
earlier from the medium than the light-quark hadrons.
