Tips on using GNC GPS port connector/adapter for Nikon D90/5000/3100/7000.

The 10-pin rectangular GPS port on Nikon is very fragile/delicate. Many D90 owners already experienced damaged/malfunctioned ports after a short period of use with various GPS cables and even remote release controller. It is not known whether Nikon recognized the issue and made the port more robust in later D90 units and D5000/D3100/D7000. Therefore care must be exercised when handling/using GPS cables.
DO NOT insert/remove GPS cable with GNC connected to camera. This will exert much downward/upward force on the connector thus putting a lot of pressure on the camera port which will result in damage in a very short time. Insert/remove GNC only with GPS cable (and/or remote release adapter)  connected.
D90/D7000 GPS port is at the bottom, GNCGN and NGPA9 GPS cables are just the right length to reach the Hotshoe GPS without stretching or bending. D5000/D3100 GPS ports are near the top. You can make a small loop on GNCGN or NGPA9 when connecting GN-1/2 or GP-1. Therefore, a shorter cable especially for D5000/D3100 is not necessary.
While GNC is designed to minimize damage to GPS port in repeated use, there is small/simple measure you can make to reduce the possible damage even further. Because GNC is designed for use with several cameras, you have to make adjustment to your particular camera.
When GNC (or any other connector such as MC-DC2) connected, it is "hanging" on the GPS port, thus allowing up/down and forward/backward movement. It is this movement that damage the GPS port in repeated use particularly in vigorously moving environment. Put a few rubber band (or similar material) loops on top and bottom of GNC so that when inserted, the top and bottom are in contact with camera body, thus eliminating/reducing up/down movement when cable is in use. This little measure goes a long way to preserving the camera port.
You do this assuming you only have one camera in constant use. If you are using more than one camera, then of course you have to leave GNC as it is so as to connect different cameras. You do not have to guess or try which way to insert GNC because there is clear marking on GNC. With D90, you see the "9" on top of GNC looking from the back of camera, while it is "5" for D5000/D3100/D7000.
Remember also that repeated inserting/removing cable from the GPS port is also a major cause of port damage however carefully you handle the cable/GPS.
Connect GNC with only cables designed for it.
DO NOT connect any other cables with Mini-USB connector. e.g. Connecting an ordinary Mini-USB data/power cable to a PC will definitely damage your camera.
If you like to make your own cable for any purpose, this is the pin assigments of GNC port.