  The double-helicity asymmetries ($A_{LL}$) of $\pi^{+}$ and $\pi^{-}$
production in polarized proton proton collisions are specially interesting
probes of the gluon's polarization. Relative differences among $A_{LL}$ of
positive, neutral, and negative pions at high transverse momentum are sensitive
to the sign and of magnitude of $\Delta$G. Quark-gluon (qg) scattering starts
to dominate mid-rapidity pion production at RHIC at transverse momenta above
5GeV/c. In this kinematic region the favored and unfavored fragmentation
functions for each pion species are sensitive to both the gluon and the quark
distributions, with different flavors having different weights for each pion
species. Charged pion asymmetry measurements will be an important component in
future global analyses, aiming to determine the gluon polarization over a wide
range in x, the most recent results using polarized longitudinal data at
$\sqrt{s}=$200GeV, are presented.
