Oh my...you want circuitboard diagrams and all those growly little electrical terms and so forth?
Sorry. I don't do electronic schematics. :(
Electrics are all just a mystery to me.
I have never hooked a camera directly to a computer. The card reader is plugged into a USB port, and I stick the memory card into that. I have several photo programs on the hard drive, and I have selected one as the default. The photo and video files are downloaded into that, and then stored in an external hard drive or on disc, as well.
But if you want to build your own card reader, I can't help you. Ask Littlefeather. I hear he has made a prototype from a four-slice toaster. Reads three different card types and burns CDs.
Killdeer