Is it possible to design a synth in csound and use that code to make an object to run in pure data?

@Fauveboy It might be.
You can certainly make them talk..... integrate them totally......
which should be as good, or maybe better as you can develop the csound synth without re-compiling a Pd object every time......
http://write.flossmanuals.net/csound/a-csound-in-pd/
David.

This creates a nice work flow you can experiment with the sound a bit more this way.

can a value be sent to the madsr object in csound from pure data to be used like a gate ?

making the sustain value a variable doesnt seem to work but perhaps this is the wrong method?