  In pp collisions at 1.25 GeV kinetic energy, the HADES collaboration aimed at
investigating the di-electron production related to $\Delta$ (1232) Dalitz
decay ($\Delta^+ \to pe^+e^-$). In order to constrain the models predicting the
cross section and the production mechanisms of $\Delta$ resonance, the hadronic
channels have been measured and studied in parallel to the leptonic channels.
The analyses of $pp\to np\pi^+$ and $pp\to pp\pi^0$ channels and the comparison
to simulations are presented in this contribution, in particular the angular
distributions being sensitive to $\Delta$ production and decay. The accurate
acceptance corrections have been performed as well, which could be tested in
all the phase space region thanks to the high statistic data. These analyses
result in an overall agreement with the one-$\pi$ exchange model and previous
data.
