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+* Overview
+
+Extends org-babel capabilities to support spice simulations using
+ngspice. Simulations are executed using an interactive ngspice process
+running in emacs. The running ngspice process can be used to
+manipulate the simulation results directly or spread a simulation into
+multiple src blocks.
+
+Spice source blocks are interpreted as circuit descriptions until an
+'.end' line is encountered. After that a control part may follow
+(surrounded by '.control' and '.endc' lines). *If there is no '.end'*
+*line all of the src block is interpreted as a control block!*
+
+* Use cases
+*** Just load some circuit for later simulation:
+#+BEGIN_SRC spice :results output
+,* RC
+r1 1 0 10k
+c1 1 0 1p
+.IC V(1)=1
+.tran 1n 0.1u
+.end
+#+END_SRC
+#+RESULTS:
+: Circuit: * rc
+
+*** Execute some stuff
+#+BEGIN_SRC spice
+echo "Hello world"
+#+END_SRC
+#+RESULTS:
+: Hello world
+
+#+BEGIN_SRC spice
+echo "0,1,2,3"
+#+END_SRC
+#+RESULTS:
+| 0 | 1 | 2 | 3 |
+
+*** Plot some voltages and return png
+#+BEGIN_SRC spice :var file="/tmp/xzy" :results file
+,*RC circuit
+r1 1 0 10k
+c1 1 0 1p
+
+.IC V(1)=1
+.tran 1n 0.1u
+.end
+
+.control
+run
+set gnuplot_terminal=png
+gnuplot $file v(1)
+.endc
+#+END_SRC
+
+#+RESULTS:
+[[file:/tmp/xzy.png]]
+
+*** Do measurements and return results
+#+BEGIN_SRC spice :session spicetest :results value
+,*Time Constant Measurement
+r1 1 0 10k
+c1 1 0 1p
+
+.IC V(1)=1
+.tran 1n 0.1u
+.print tran v(1)
+.end
+
+.control
+run
+meas tran value_at_tau find V(1) at=1e-8
+meas tran value_at_five_tau find V(1) at=5e-8
+echo $&value_at_tau ,$&value_at_five_tau
+.endc
+#+END_SRC
+
+#+RESULTS:
+| 0.36798 | 0.00671732 |
+
+*** write simulation data to file and return file name
+#+BEGIN_SRC spice :var file="/tmp/xyz" :post plot_stuff(data=*this*) :results file
+,*RC circuit
+r1 1 0 10k
+c1 1 0 1p
+.IC V(1)=1
+.tran 1n 0.1u
+.end
+.control
+run
+wrdata $file v(1)
+.endc
+#+END_SRC
+
+#+RESULTS:
+[[file:/tmp/xyz_plot.png]]
+
+#+NAME: plot_stuff
+#+BEGIN_SRC gnuplot :var data="x" :file "/tmp/xyz_plot.png" :results silent
+plot data u 1:2 w l ls 1
+#+END_SRC
+
+* Flags
+** :netlist / :circuit
+Name of a src block to include for netlist/circuit descriptions.
+** :dir
+Working directory to run the src block in. Default is the value of `default-directory'.
+** :file?
+
+** :gnuplot
+Name of gnuplot block or .plt file: handle plotting instead of gnuplot
+lines
+** :results
+Available result options are `value' which returns the output of the
+ last expression, `output' which returns all output and `smart' which
+ tries to only display echos and plot filenames.
+** :batch / :no-interactive
+use batch mode