This page describes the steps I went through in my project to connect a Garmin eTrex Summit GPS device to a Nikon D200 camera body in order to record location information in the EXIF data of images captured using the setup. While this procedure worked fine for me, I do not take any responsibility for you or your equipment should you try this yourself. All images can be found in the "Equipment" photoset on my flickr account, here. A parts list in PDF format can be downloaded here.

There are seven steps:


Step 1 - The circuit diagram and initial circuit layout
Step 2 - Soldering the components and jumpers to the breadboard
Step 3 - Constructing the box to house the GPS
Step 4 - Second stage of soldering, fixing camera and GPS cables, and fitting remote release socket
Step 5 - Making the false floor to support the GPS and protect the circuitry and components
Step 6 - Painting/finishing
Step 7 - Constructing new Garmin to PC cable and downgrading GPS firmware



The first step is to figure out the circuit diagram, below:

GPS - Nikon D200 diagram.jpg

Clicking on the image (or middle-clicking to open it in a new tab) opens the flickr photo page for this image, allowing notes and comments to be seen, and allows one to view the full-size version of the image. It is important to read the notes as they clarify parts of the circuit, and in some case suggest changes that never made it on to the diagram.

Once you've spent some time getting your head around the diagram, the circuit can then be translated onto breadboard, as shown in the image below:

D200 GPS project - component layout on breadboard

The black ink denotes the locations of actual components. The two red bits denote where it is necessary to bridge the copper rows with little bits of wire to complete the initial stage of the circuit construction. This does not include the locations of earth/ground wires as it would get far too complicated- these are added later simply with reference to the circuit diagram.

Before it is possible to begin work soldering the components that make up the circuit, it is necessary to first remove a strip of copper from the conductive side of the breadboard, as shown below:





The next step is to solder on the components, starting with the dual-in-line socket, then the capacitors, then resistors. Next, the little wire jumpers mentioned earlier, then the jumpers to connect the grounded areas together and to the earth/ground strip running along the top of the circuit.


As can be seen in the image above, the wire jumpers in red complete the circuit where the solid components couldn't stretch the distance required or were obstructed by other components, and the black wires and two pieces of bare wire on the right-hand side connect together the inputs/outputs required to be grounded/earthed. This completes the first stage of soldering - cables from the camera, GPS and remote release must all be connected, but this cannot be done until a box is made to house the GPS, as the cable from the camera will pass through a hole in the side of this box and will therefore have to soldered towards the end of the project.



I chose to make my GPS-holding box out of aluminium, as it is lightweight, easy to work with, and is easier to use in conjunction with adhesives and epoxy glues than plastic. Begin by obtaining the dimensions of your GPS unit and making a cardboard mockup of the design, to ensure that everything fits. This will also give you a template from which to mark your aluminium for cutting and bending. In plan view, a rectangular box is a squashed "+" symbol, and when the edges are bent at a 90 degree angle it should turn into a box not dissimilar to this one:


The hole in the base of the box in the picture above is to accommodate another smaller box which fits into the gap and holds the circuitry in my version of the project - I underestimated the height of components in the circuit such as the capacitors, and did not account for the thickness of solder and electrical tape, so I ended up with a box too shallow to hold both the circuitry and the GPS. Rather than start again and construct a new box, I decided instead to sink another box through the floor to accommodate the circuitry, much in the style of a sunken bath tub. This is possible because as can be seen below, the depth afforded by the aluminium accessory shoe fitted to the bottom of the box is sufficient to allow adequate clearance above the camera's pentaprism for such a sunken compartment:


With the sunken compartment added (if opted for) and the accessory shoe attached, the box will probably look something like this:


Next the accessory shoe, and the sunken compartment if applicable, can be permanently fixed to the aluminium box. Make sure that there is sufficient play in the accessory shoe's locking nuts to allow it to be easily attached to and removed from the camera's hot shoe. To fix the components together I used a two part epoxy chemical weld, being sure to follow the instructions on the packet and to roughen up the surfaces to be glued beforehand with some coarse sandpaper.



Once the epoxy weld (or other fixing method) has had time to sufficiently cure or dry, work can begin with the next stage- drilling holes for cables and fittings to pass through the box's body, and then the fitting of the cables from the camera, the GPS device, and the 3.5mm stereo socket for use with the remote release. The best place for the remote release socket is probably on the far side of the box, farthest away from the viewfinder, either on the left- or right-hand side depending on your preference. The best entry point for the cable from the camera is wherever you think it won't get in your way, or in the way of the circuitry to go in the box. Keep it as low down as possible to leave as much room as you can for the GPS unit itself. Rather than passing through the potentially sharp aluminium sheet unprotected, it is recommended that a suitably-sized grommet is employed to protect the cable from the camera. The image below might give an idea of what to aim for at the end of it all:


The specifications and pin-out of the Garmin plug can be found here and here, and in case you want to verify the pin-out of your Nikon 10-wire cable, the specifications of that can be found here. Information regarding the wires to use for a remote release can be found here.

Once you've soldered the wires from the camera, GPS, and remote release socket, you should have something along these lines:

Nikon D200/D2x GPS project, part-done, plan view 



The next step is to construct a floor for the box, to protect the circuitry and elevate the GPS above the wires, components and the accessory shoe fixing. Again, start by making a cardboard template to check that you have your measurements correct before you commit to cutting into your aluminium. Leave a slot down one side to allow sufficient movement of the GPS cable.





Aluminium is difficult to get paint to stick to, so this property of the material, along with my laziness, contributed towards the decision to not paint the box, but rather to cover it in black gaffer tape. One thing to point out though is that gaffer tape and super glue don't seem to mix all that well, as shown below:


The finished article, with false floor fitted:




Depending on the GPS unit you purchase, and its age, it may not work with this project right out of the box (as discovered here). This is apparently due to a power saving feature of new firmware which means that the GPS will only send data if it is receiving data - as the camera does not "talk" to the GPS, this causes problems. The solution, as suggested by the above-linked forum page, is to downgrade the firmware on the GPS to the last version known to work. In the case of my GPS unit, a Garmin eTrex Summit, this meant downgrading the firmware from 3.51 to 3.30. Previous versions of Garmin firmware can be found here, and the instructions for the procedure here.

The problem now however is that you may have already butchered your Garmin serial cable as part of the project to connect to your camera before finding this out, as I did. The solution need not be costly though as it is quite possible to construct a makeshift Garmin connector from an old plastic card and a cheap DB9 modem serial cable- if you don't find one lying around somewhere you should be able to pick one up on eBay for around £1.



More information regarding this procedure will be added shortly, as I have not yet received delivery of my eBay serial cable. For the time being, you can find info here.



One thing I recently realised while away in Krakow for a weekend is that when using the brown wire from the camera for power, the circuit will draw a current even when the camera is turned off. If, for example, you were to turn everything off and put your camera away for the night, but without first disconnecting the GPS circuitry, you will wake up in the morning with a flat battery. As it was only a two day visit I hadn't taken a charger either. You live and learn.

A better option here would be to use the grey wire from the camera for the circuit's power source, as with this the circuitry would only draw power when the camera's meter was on, thereby prolonging battery life. I haven't tried this, but I don't see why it wouldn't work. You can find a pin-out diagram and information table for the Nikon 10-pin connector here (opens in a new window/tab).




If you can afford to have a GPS device dedicated solely to adding EXIF data to images, then you might want to consider an option like this one, which builds a GPS chip into the casing of the Nikon MC-35, resulting in a small and neat little package.