Matt Segal underwater photography - reports

Adding USB Connectivity to your U/W Housing

USB Connector Pin Layouts It took only a couple liveaboard trips to convince me that there had to be an easier solution to downloading photos from the camera. Opening the housing after each dive, and either swapping out the memory card, or plugging in a USB cable to the side of the camera, was not only an inconvenience, but exposed the housing to an increased chance that a small hair or other contaminant might land on the main o-ring, leading to a flood.

With the long battery life of the majority of dSLR cameras, the size of the memory card becomes the limiting factor, and with RAW files on some cameras breaking 15mb, one can only shoot so many pictures before the card fills up. Determined, I set about trying to find a way to transfer files over USB through the housing.

A little research on USB, and I found two important qualities. The first is that USB is only four pin. An immediate solution should come to mind – Ikelite-style sync cords are five pin. The second is that the cable is shielded – this presented some minor issues later in the process.Original and modified Ikelite 20D housing

Regardless, I contacted Ikelite about having another sync-cord bulkhead installed (in addition to having my previous sync-cord bulkhead converted to the newly released right-angle bulkhead). Note the comparison photo of the old and converted backplates.

The top bulkhead is what I was concerned with. On the inside of the housing, Ikelite conveniently left me approximately 6” of wire, with the five leads stripped at the end. I promptly cut a USB2 rated cable in half. Note that this is a cable with a Standard Type A connector on one end, and a Mini Type B on the other end (as pictured above), and can be found both online and at most local computer and electronics stores.

In addition to the modified housing, Ikelite included in the box (at my request), their ICS Plug (#9014.15), along with the pins and receptacles for the rubber grommet they fit into. After vigorous checking with a multimeter, I soldered one end of the cut USB cable to the pins and receptacles, and assembled the plug connection. USB-Ikelite sync cableThe bastard child of a USB cable and sync-cord was born.

It should be noted that there were no issues with cutting away the shielding with the previous step, and the cable worked as planned. Attaching the USB mini-plug inside the housing was not as cut-and-dry. Of primary concern was the issue of space, and lack of it. Ikelite has made great strides in reducing the size of the dSLR housings, and this required some creative wiring. In addition, the plastic mold on the plug itself jutted out too far, and would not clear the side of the housing when plugged into the camera, so this was trimmed down until everything fit, albeit snugly.

When wiring up the USB mini-plug to the pre-exposed leads connected to the bulkhead, and testing by plugging into the computer along the way, it was noted that some positioning of the wires led to “USB Device Not Recognized” and “USB Device Not Responding” errors. I took a hard look at the full USB specifications, and noticed that it was specified that the data wires be a twisted pair for the entire length of the cable, and that there be an independent shield ground (isolated from the black GND wire) that connected the external metal plug connectors on each of the USB cables.

After rewiring and soldering together both the internal connector and the external cord to adjust for the twisted-pair requirement, and using the braided stainless steel shielding cable from the original USB cord as the independent ground, I again plugged the setup into the computer, and was rewarded with the Canon capture program opening and a successful recognition of the camera. A few test shots and image downloads later, and I decided to route the internal cable forward to the front of the eTTL2 converter, and then loop it back to the camera's USB port on the left side. Testing showed that this did not impede any of the camera button functions nor viewing ability. USB cable attached to camera inside housing

With the camera installed, both the eTTL2 connector and USB connector can be plugged in before the housing is sealed. Here, the USB connector is seen plugged into the side of the camera.

I have not yet run any technical tests on the speed of the transfer, or if it suffered at all due to the cutting of the cable and possible minor signal loss that can occur with any such procedure. However, in casual testing, all RAW files are transferred off the camera at a rate similar to that of the camera outside of the housing (a direct connection). In addition, the Canon Capture program works as well, allowing for USB control of the camera remotely, opening up capabilities for “polecam” use and underwater time-lapse photography. Obviously, steps would need to be taken that the external connector cord is made waterproof (or retrofitted to a waterproof sync-cord).

I am happy to conclude that the idea of being able to download straight from the housing was not only feasible, but fully achievable. There is still lots of room for streamlining the finished product (including the possibility of a right-angle, low-profile mini type B connector), but I’m content to simply enjoy the functionality for the time being.

Ikelite Canon 20D Housing with USB Connectivity
Completed USB connectivity mod
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