There are a bunch of different cables needed to connect the controller, camera and perhaps additional equipment like a pan/tilt head and its controller.
When I was still waiting for my rail and controller’s parts to arrive, I started with building the shutter cables (2.5mm jack and N3 – for Canon EOS 500D and 6D).
I used the 2.5mm stereo jack with a cable I have ordered and soldered on a 3.5mm stereo jack on the other side. Pretty easy. This one’s for the 500D and similar models.
For the second cable I used a 7$ remote with N3 plug, since these canon plugs can apparently not be bought separately. Cut the cable off the remote and soldered it to three ordinary wires, tore the wires through a shrink tubing and soldered on the 3.5mm stereo jack on the other end. Shrinked the tubing and that was it. As for the wiring of the jacks I asked Google and found a couple of blog articles and images, telling me which colors should go to which parts of the jacks etc. I don’t have the links anymore, they shouldn’t be too hard to find though, just google “wiring n3”, “wiring 3.5mm jack” and similar terms.