Add step to the documentation build that compiles diagrams from latex…

…/tikz source into PNG files that can be included from Doxygen. Added diagram for a Costas loop.

Makefile

@@ -47,5 +47,6 @@ clean:
 	done
 
 docs:
+	$(MAKE) -C docs/diagrams
 	doxygen docs/Doxyfile
 

docs/Doxyfile

@@ -720,7 +720,7 @@ EXAMPLE_RECURSIVE      = NO
 # directories that contain image that are included in the documentation (see 
 # the \image command).
 
-IMAGE_PATH             = 
+IMAGE_PATH             = docs/diagrams/
 
 # The INPUT_FILTER tag can be used to specify a program that doxygen should 
 # invoke to filter for each input file. Doxygen will invoke the filter program 

docs/diagrams/Makefile

@@ -0,0 +1,17 @@
+
+DIAGRAMS = costas_loop.tex
+
+PDFS = $(DIAGRAMS:.tex=.pdf)
+
+PNGS = $(PDFS:.pdf=.png)
+
+all: $(PNGS)
+
+%.pdf: %.tex
+	pdflatex $<
+
+%.png: %.pdf
+	 convert -density 120 -trim -bordercolor White -border 20 $< $@
+
+clean:
+	rm *.aux *.log *.pdf *.png

docs/diagrams/costas_loop.tex

@@ -0,0 +1,52 @@
+\documentclass{article}
+\pagestyle{empty}
+
+\usepackage{tikz}
+\usetikzlibrary{shapes,arrows}
+\begin{document}
+
+\input{tikz_styles.tex}
+
+\tikzstyle{mix} = [draw, circle, node distance=1cm, minimum size=0.7cm]
+\tikzstyle{input} = [coordinate]
+
+\begin{tikzpicture}[auto, thick, node distance=1.5cm, >=stealth']
+
+  \def\h{2.5cm}
+
+  \node [input, name=input] {};
+  \node [input, right of=input, name=split] {};
+  \node [block, right of=split, node distance=2cm] (nco) {Carrier NCO};
+  \node [mix, above of=nco, node distance=\h] (Imix) {};
+  \node [simpleblock, below of=nco, node distance=\h*0.4] (Qphase) {$\frac{\pi}{2}$};
+  \node [mix, below of=nco, node distance=\h] (Qmix) {};
+  \node [block, right of=nco, node distance=3.5cm, text width=2cm] (filter) {Loop filter \\ $D[z]$};
+  \node [block, above of=filter, node distance=\h, text width=2cm] (Idump) {Integrate \& Dump};
+  \node [block, below of=filter, node distance=\h, text width=2cm] (Qdump) {Integrate \& Dump};
+  \node [block, right of=filter, node distance=3.5cm] (desc) {Discriminator};
+
+  \draw [->] (input) -- node {$x(n)$} (split);
+  \draw [->] (split) |- (Imix);
+  \draw [->] (split) |- (Qmix);
+  \draw [->] (Imix) -- node {$x_i(n)$} (Idump);
+  \draw [->] (Qmix) -- node {$x_q(n)$} (Qdump);
+  \draw [->] (Idump) -| node[near start, above] {$I(n)$} (desc);
+  \draw [->] (Qdump) -| node[near start, above] {$Q(n)$} (desc);
+  \draw [->] (desc) -- node {$\varepsilon(n)$} (filter);
+  \draw [->] (filter) -- node {$\tilde f(n)$} (nco);
+  \draw [->] (nco) -- node {$\tilde x_i(n)$} (Imix);
+  \draw [->] (nco) -- (Qphase);
+  \draw [->] (Qphase) -- node[left] {$\tilde x_q(n)$} (Qmix);
+
+  \draw [-] (Imix.south west) -- (Imix.north east);
+  \draw [-] (Imix.south east) -- (Imix.north west);
+  \draw [-] (Qmix.south west) -- (Qmix.north east);
+  \draw [-] (Qmix.south east) -- (Qmix.north west);
+
+  \node [above right of=Imix, node distance=0.7cm] {\textbf{I}};
+  \node [below right of=Qmix, node distance=0.7cm] {\textbf{Q}};
+
+\end{tikzpicture}
+
+\end{document}
+

docs/diagrams/tikz_styles.tex

@@ -0,0 +1,15 @@
+% Define some styles for use in Tikz diagrams.
+
+\tikzstyle{simpleblock} = [draw, rectangle, minimum height=2em, minimum width=1em]
+
+\tikzstyle{block} = [
+  draw=blue!50!black!50,
+  very thick,
+  top color=blue!5,
+  bottom color=blue!15,
+  rounded corners=1.5mm,
+  rectangle,
+  minimum height=2em,
+  minimum width=1em,
+  text centered
+]