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Faust.md

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+# Using Faust DSP language in the VCV Prototype 
+
+The [Faust audio DSP language](https://faust.grame.fr) can be used in VCV Prototype. The compiler can be embedded in applications or plugins using [libfaust](https://faustdoc.grame.fr/manual/embedding/), and DSP code can be edited and JIT compiled on the fly.
+
+## Compiling on OSX
+
+The Faust *libfaust* library will have to be compiled as a dynamic version, and installed on your machine. Then the [Faust aware VCV Prototype](https://github.com/sletz/VCV-Prototype) can be compiled and installed.
+
+- clone the [Faust GitHub project](https://github.com/grame-cncm/faust)
+- assuming you have installed the LLVM dependency (with brew or macports on OSX), type `make world` to compile the libfaust libray in dynamic mode (read https://github.com/grame-cncm/faust/wiki/Building if needed)
+- clone the [Faust aware VCV Prototype](https://github.com/sletz/VCV-Prototype)  then type `make && make install` to build it
+- you can now add a Faust aware VCV Prototype in your Rack session and start coding in Faust.
+
+## Loading/editing/compiling .dsp files
+
+Faust DSP files have to be loaded in VCV Prototype and edited in a external editor (Visual Studio Code, Atom...). Each time the file is saved, it will be recompiled and executed. To possibly save compilation time, the DSP machine code is saved in a cache, and possibly restored the next time the session will be loaded.
+
+The 6 *switches*, *knobs* as well as the *lights* and *switchLights* can be connected to UI controllers using metadata:
+
+- `[switch:N]` (with N from 1 to 6) has to be used in a `button` or `checkbox` item to connect it to the prototype interface switch number N.
+- `[knob:N]` (with N from 1 to 6) has to be used in a `vslider`, `hslider`  or `nentry` item to connect it to the prototype interface knob number N.
+- `[light_red|green|red:N]` (with N from 1 to 6) has to be used in a `vbargraph` or `hbargraph` item to connect it to the prototype interface light number N.
+- `[switchlight_red|green|red:N]` (with N from 1 to 6) has to be used in a `vbargraph` or `hbargraph` to connect it to the prototype interface switchLight number N.
+
+The [faust_libraries/rack.lib](https://github.com/sletz/VCV-Prototype/blob/master/faust_libraries/rack.lib) Faust library contains usefull functions to convert VC signals, and can be enriched if needed. 
+
+## DSP examples
+
+Here is a simple example showing how oscillators can be controlled by UI items:
+
+```
+import("stdfaust.lib");
+
+// UI controllers connected using metadata
+freq = hslider("freq [knob:1]", 200, 50, 5000, 0.01);
+gain = hslider("gain [knob:2]", 0.5, 0, 1, 0.01);
+gate = button("gate [switch:1]");
+
+// DSP processor
+process = os.osc(freq) * gain, os.sawtooth(freq) * gain  * gate;
+```
+
+Some additional files can be seen in the examples folder:
+
+- [synth.dsp](https://github.com/sletz/VCV-Prototype/blob/master/examples/synth.dsp) demonstrates how to use all different Prototype UI items
+- [organ.dsp](https://github.com/sletz/VCV-Prototype/blob/master/examples/organ.dsp) demonstrates a MIDI controllable additive synthesis based organ
+- [physicalmodel.dsp](https://github.com/sletz/VCV-Prototype/blob/master/examples/physicalmodel.dsp) demonstrates a model synthesis bell connected to a reverb