\begin{tikzpicture}[dia/.style={text centered, draw, align=center, inner sep=2mm, minimum height=1.3cm, rounded corners=0.2cm}, font=\sffamily]
    \footnotesize
    \node[dia] (sequencing) {Sequencing};
    \node[dia, right=12mm of sequencing] (basecall) {Basecalling};
    \node[dia, right=12mm of basecall] (prealign) {Pre-alignment};
    \node[dia, right=8mm of prealign] (process) {Read\\ processing};
    \node[dia, right=8mm of process] (realign) {Re-alignment};
    \node[right=6mm of realign] (out) {};

    \draw[-Latex] (sequencing) -- node[midway, above] {\scriptsize Signal} (basecall);
    \draw[-Latex] (basecall) -- node[midway, above] {\scriptsize Bases} (prealign);
    \draw[-Latex] (prealign) -- (process);
    \draw[-Latex] (process) -- (realign);
    \draw[-Latex] (realign) -- (out);

    \draw[-Latex] (sequencing.south) 
        |- node[pos=0.75, above] {\scriptsize Signal} 
        ([yshift=-10mm]process.south) 
        -| (process.south);
\end{tikzpicture}