While the interface to the computer is done via Serial interface,
its going to be pretty tough to make a DIY "cable" for the Oceanic/Aeris/Sherwood/
computers.
I looked at it for a while and can offer some details.
Oceanic contracted through a design house to custom make this cable and write
the driver for it. It appears that FTDI was used to create the product.
The existing cable isn't really just a cable. It is a USB to serial converter.
It uses a FTDI chip to do the USB to Serial conversion. The chip is FT232BM.
You can look it up on the FTDI website for details.
Assuming you still want to try making a cable here is some more information.
The first stumbling block will be mechanical. (for the connector itself)
The connector uses a mechanical fitting that has 3 spring loaded pins that push against
against the 3 metal ridges in the computer and even slightly retract under the slight
pressure when you insert the connector in the computers data port socket.
I always thought that it should be possible to find this connector. I've been
unsuccessful trying to locate this connector. I had thought that it might even be used
on a cell phone and that perhaps an off the shelf cell phone data cable might be used.
I've had no luck trying to locate anything that would work.
The best thing to do would probably be to actually contact FTDI and see if they
could give you the connector source.
The second stumbling block will be s/w related.
While Oceanlog & ACI s/w do use a serial interface it isn't a simple rs232 serial
that uses a standard PC uart. It goes through the FTDI USB to serial chip.
When the s/w starts up up it goes and reads a few hives in the registry and starts
walking the serial ports on the machine looking for one that is attached to their
download driver. Its been a while but I believe that theirs is a virtual serial port.
So as long as you could figure out what they trigger on in the registry and mimick
that, you should be able to trick the OceanLog/ACI s/w to use somebody elses
serial port driver.
An alternative route might be to see if you could find an existing USB to serial device
that used the FTDI FT232BM chip. Then go edit the driver .inf files that come with
with the data cable driver from Oceanic/Aeris (which can be download for free)
and trick it into loading their drivers on the USB to serial data cable that you "DIY".
You will need to know the USB Device ID, Vendor ID, and subVendor ID of your device so
that you can insert the proper values in the Oceanic/Aeris .inf driver file to trick
windows into loading it for this alternate h/w.
So while I do think it is possible to create a DIY Oceanic/Aeris data cable,
it will be pretty tough. The mechanical component is one area that there doesn't
seem to be much room for creating something that would work.
Oh, one other thing is that up until now, the same driver is used to run
the data cable for all 3 dive computers. So while they are in fact slightly
different and can be identified by unique IDs, they are interchangeable
because the s/w is currently not checking to ensure the exact same brand
of data cable is being used as the computer.
i.e. you can use an Aeris cable on a Oceanic computer or a Oceanic cable
on an Aeris (which is what I'm doing).
This might be helpful as there often is a price difference between the different
brands.
I don't know if Oceanic will continue have a single driver for all the data cables,
but they do for now.
Hope that helps.
--- bill