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On TeXample, Martin Scharrer contributed an excellent d-flipflop example that simplifies circuit drawing to a two step-process of

  1. Place the part:

    % Place FFs  
    \foreach \m in {0,...,\N}  
          \node [shape=dff] (DFF\m) at ($ 3*(\m,0) $) {Bit \#\m};
  2. Connect the nets

The d-flip flop uses a \pgfdeclareshape command and involves 120-lines of code. It's possible to save the d-flip-flop in its own file that looks something like the following:

  % D flip-flops (DFFs) and shift register  
  % Original Author: Martin Scharrer  
  % Data Flip Flip (DFF) shape  
    %... details omitted, available elsewhere  

 % Define styles, etc  
    every dff node/.style=%... details omitted, available elsewhere  

This may be a tall order, but is there a tool, similar to TikZit, that is stable under Windows and allows creation, and editing of graphics saved in this manner?

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As far as I know there isn't one, but it would be create to have one. Some vector graphic tools can produce TikZ (or PGF) I heard, but I doubt they can produce a full shape declaration. You could, however, use it to at least do the backgroundpath etc. part of the shapre. – Martin Scharrer Feb 23 '11 at 14:29
(To get a block of code formated inside a list, you have to intend it by 8 spaces.) – Caramdir Feb 23 '11 at 21:25
Thanks to you both. I should mention that there is a related question here. I've tested most, but while they export (verbosely) to tex, few import. – SmileAndNod Feb 23 '11 at 22:35
up vote 1 down vote accepted

As an interim solution to this question, I've settled on using the \matrix command to position coordinates. Eventually I would like to see a simple graphical utility or other such parser that can take a VHDL template or schematic symbol and automatically generate the source-code for the IC, using the following as a template:

%% An IC is essentially a matrix with connection points (coordinates) at its upper, lower, left and right edges.
%% The matrix command facilitates this nicely using nodes combined with the label option
%% The matrix command for any IC can be placed in a custom command for reuse: 
%% Use the folllowing as a template
    \matrix (DFF#1) [draw,very thick,inner sep=0pt,outer sep=0pt,column sep=2pt,label distance=0.6ex, 
        ampersand replacement=\&] at #2 {
            % Top Row:
            \& \& \& \& \& \node [coordinate,label=270:R] (R#1) {}; \& \& \& \& \& \&\\
            % Left and right rows:
            \& \& \& \& \& \& \& \& \& \& \& \\[1ex]
            \node [coordinate,label=0:D] (D#1) {};
            \& \& \& \& \& \& \& \& \& \& \& \node [coordinate,label=180:Q] (Q#1) {}; \\[6ex]
            \node [coordinate,label=0:CE] (CE#1) {};
            \& \& \& \& \& \& \& \& \& \& \& \\
            \& \& \& \& \& \& \& \& \& \& \&
                \node [coordinate,label=180:$\overline{\text{Q}}$] (Qb#1) {}; \\
            \node [label=0:$\large >$,anchor=west] (CLK#1) {};
            \& \& \& \& \& \& \& \& \& \& \& \\[1ex]
            % Bottom row:
            \& \& \& \& \& \node [coordinate,label=90:S] (S#1) {}; \& \& \& \& \& \&\\
    } ;

Once the symbols are defined, graphical software that manipulates a grid can define coordinates where ICs and I/O markers are to be placed. The output of this software should look something like:

{[start chain=placements]
%% Place the parts

% D registers, with labels
%% Step 1: anchor placement (a graphical editor should be able to handle this)
    \foreach \m in {0,...,\N}
        \node [coordinate] (tlDFF\m) at ($ 3*(\m,0) $) {};

% 'Reset' port label
    \path (tlDFF0) +(-2,+2.5) coordinate (reset)   node [anchor=east] {reset};

% 'Set' port label
    \path (tlDFF0) +(-2,-2.5) coordinate (set)   node [anchor=east] {set};

% Clock port label
    \path (tlDFF0) +(-2,-3) coordinate (clock) node [anchor=east] {clock};

% Clock enable port label
    \path (tlDFF0) +(-2,-3.5) coordinate (clocken)   node [anchor=east] {clock enable};

The third task would be simply to place the appropriate symbols at the coordinates. This is just a matter of picking unique names, and placing the shape as follows:

\foreach \m in {0,...,\N}

%% annotate the ics as desired
\foreach \m in {0,...,\N}
    \node [fit=(DFF\m),font=\sffamily\scriptsize] {Bit \#\m};

%% Place input and output ports, junctions, etc:
    % data in- and output port
    \path [ultra thick] (D0) -- +(-1,0) node [anchor=east] (in0) {input} ;
    \path [ultra thick] (Q\N) -- +(1,0) node [anchor=west] (out\N) {output};

Finally, connect the nets with wires. The graphical routine need only be able to identify what coordinate is being referenced when the user clicks on a specific location in the image. Drawing can be accomplished using the \chainin command, similar to that shown below:

{[start chain=nets]
%% Connect the nets

% Connect reset lines
    \chainin (reset);
    {[start branch=reset] 
        \foreach \m in {0,...,\N} 
            \chainin (R\m) [join=with reset by {hv path,tip}];

% Connect FFs (Q1 with D1, etc.)    
\chainin (in0);
\chainin (D0) [join= by ultra thick];

    \foreach \m in {1,...,\N} {[start branch=qd\p\m] % Note that it starts with 1, not 0
        \chainin (Q\p);
        \chainin (D\m) [join=by ultra thick];

\chainin (Q\N);
\chainin (out\N) [join= by ultra thick];

% Connect set lines
    \chainin (set);
    {[start branch=set] 
        \foreach \m in {0,...,\N} 
            \chainin (S\m) [join=with set by {hv path,tip}];

% Connect clock lines
    \chainin (clock);
    {[start branch=clk]
        \foreach \m in {0,...,\N} 
            \chainin (CLK\m) [join=with clock by {Z path=-0.55,tip}];

% Connect clock-enable lines
    \chainin (clocken);
    {[start branch=clken]
        \foreach \m in {0,...,\N}  
            \chainin (CE\m) [join=with clocken by {Z path=-0.75,tip}];    

Any reports of progress in this matter are appreciated!

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