documentclass[12pt, a4]{article}

usepackage{microtype}
usepackage{fontspec}
usepackage{hyperref}
usepackage{xltxtra}
usepackage{xgreek}
setmainfont[Mapping=tex-text]{Liberation Sans}

usepackage{listings}
input{listcode}

begin{document}
    english text : hello

    greek text   : γεια σου

    lstinputlisting{my_code.ino}
end{document}

lstset{
language=C,
basicstyle=ttfamily,
breakatwhitespace=false,
breaklines=true,
captionpos=b,
commentstyle=usefont{T1}{pcr}{m}{sl}color{red},
deletekeywords={},
firstnumber=1,
frame=leftline,
framerule=2.0pt,
numbers=left,
numbersep=10pt,
numberstyle=tinycolor{red},
rulecolor=color{green},
showstringspaces=false,
showtabs=false,
stepnumber=1,
stringstyle=color{blue},
tabsize=2,
}

void setup(){
}

void loop(){
    //english remarks
    //ελληνικά σχόλια
}