This guide first explains some advanced features of the Barotrauma reactor system and then combines a PD controller with some reverse engineering of Barotrauma's source code to build a working fission controller. This guide does not build a turbine controller. Please see Rob Smith's video for a really great turbine controller that works well with this fission controller.
If you don't care about the details, just copy the following setup to your submarine. The wiring should be pretty self-explanatory from the layout, with the wires always going from the left to the right.
Component list (thanks to @FinetalPies):
- 4 WiFi
- 6 Memory