Block Diagrams in TikZ

for my thesis i need to put some block diagrams in my LaTeX document. I was recommended to use TikZ for that.
This is the only sample code i could find.

Do you guys maybe have some tutorials / doc on that?

Especially i am interested in how to put graphical symbols into the boxes instead of text. And how to draw a dashed box around blocks.

Something like:

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Here are two out of many relevant questions to get you started: Left and right align inside one tikz rectangular node and more advanced but probably more helpful (in fact might be a duplicate : Flow (or block) diagram tips?. Search for block diagrams on this site too. –  percusse May 9 '12 at 23:50
Look at thread How to create new node shapes? from pgf-users mail list. There, Mark Wibrow show some examples of new blocks with drawings inside. –  Ignasi May 10 '12 at 7:12
Thank you very much, that gets me started. –  bijan May 10 '12 at 11:23

To put a drawing into a block, I advise you to create some macros with your drawings and put them in the nodes as in the example below

\documentclass[border=10]{standalone}
\usepackage{tikz}
\usetikzlibrary{positioning}

\newcommand{\symbolA}{
\tikz \draw[red] (0,0)--(0,0.2)--(0.2,0.2)--(0.2,0.4)--(0.4,0.4);
}

\newcommand{\symbolB}{
\tikz[y={(0,-1)}] \draw[blue] (0,0)--(0,0.2)--(0.2,0.2)--(0.2,0.4)--(0.4,0.4);
}

\newcommand{\symbolC}{
\begin{tikzpicture}
\draw[fill=green] (0,0) circle (0.2cm);
\end{tikzpicture}
}

\begin{document}

\begin{tikzpicture}
\node[draw](A) at (0,0){\symbolA};
\node[draw, right=2em of A] (B) {\symbolB};
\node[draw, right=2em of B] (C) {\symbolC};
\draw[-latex] (A) -- (B);
\draw[-latex](B) -- (C);
\end{tikzpicture}

\end{document}


of course you can use it with the code you quote

\documentclass[border=10]{standalone}
\usepackage{tikz}
\usetikzlibrary{positioning,shapes,arrows}

\newcommand{\symbolA}{
\tikz \draw[red] (0,0)--(0,0.2)--(0.2,0.2)--(0.2,0.4)--(0.4,0.4);
}

\newcommand{\symbolB}{
\tikz[y={(0,-1)}] \draw[blue] (0,0)--(0,0.2)--(0.2,0.2)--(0.2,0.4)--(0.4,0.4);
}

\newcommand{\symbolC}{
\begin{tikzpicture}
\draw[fill=green] (0,0) circle (0.2cm);
\end{tikzpicture}
}
\begin{document}

\tikzstyle{block} = [draw, fill=blue!20, rectangle,
minimum height=3em, minimum width=6em]
\tikzstyle{sum} = [draw, fill=blue!20, circle, node distance=1cm]
\tikzstyle{input} = [coordinate]
\tikzstyle{output} = [coordinate]
\tikzstyle{pinstyle} = [pin edge={to-,thin,black}]

% The block diagram code is probably more verbose than necessary
\begin{tikzpicture}[auto, node distance=2cm,>=latex']
% We start by placing the blocks
\node [input, name=input] {};
\node [sum, right of=input] (sum) {};
\node [block, right of=sum] (controller) {\symbolA};
\node [block, right of=controller, pin={[pinstyle]above:Disturbances},
node distance=3cm] (system) {\symbolB};
% We draw an edge between the controller and system block to
% calculate the coordinate u. We need it to place the measurement block.
\draw [->] (controller) -- node[name=u] {$u$} (system);
\node [output, right of=system] (output) {};
\node [block, below of=u] (measurements) {\symbolC};

% Once the nodes are placed, connecting them is easy.
\draw [draw,->] (input) -- node {$r$} (sum);
\draw [->] (sum) -- node {$e$} (controller);
\draw [->] (system) -- node [name=y] {$y$}(output);
\draw [->] (y) |- (measurements);
\draw [->] (measurements) -| node[pos=0.99] {$-$}
node [near end] {$y_m$} (sum);
\end{tikzpicture}
\end{document}


But you can also use the Schemabloc package: http://www.texample.net/tikz/examples/schemabloc/.

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Nesting TikZ pictures is ... problematic. One could just draw the symbols on top of the nodes afterwards, or do it the other way around: draw the node under the symbol. –  Loop Space May 10 '12 at 9:13
Thanks so much for your effort! –  bijan May 10 '12 at 11:27
hi Andrew, I don't understand "Nesting TikZ pictures is ... problematic. ", Can you explain, with an example –  rpapa May 10 '12 at 17:25