It seems OpenSCAD is capable of importing of both ASCII and binary STL files. As such, this is probable the most convenient and likely also only choice for making stl to scad conversion work. We do not know about any other 3rd party software that could perform this conversion.
Convert Stereolithography CAD file to OpenSCAD CAD model.
We have found one software suitable in our database for this conversion.
Multiplatform software - convert stl to scad on any platform
OpenSCAD is a software for creating solid 3D CAD objects. OpenSCAD is not an interactive modeller. Instead it is a 3D-compiler that reads in a script file that describes the object and renders the 3D model from this script file. It is free software and available for Linux/UNIX, MS Windows and Mac OS X.
Convert from stl file
to scad file
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.