Communication among briefcase halves

Question

I'm building a small laptop-ish device in a briefcase. Imagine the green wires aren't there. The LCD half lies somewhat deeper in its case than the keyboard part.

For now, testing and programming, I'm using four wires (2x I2C, ground, 5V) to connect the both parts. However, that isn't that neat. When closing the case for example, you should look after the wires in order for them to stay in the case. First solution of course is shorter wires, but that wouldn't be that neat either.

So what I'm looking for is a neat way to do the inter-board communication. It should be easy to handle and robust.

The normal way to do this in a laptop is to wire it through the hinges. This isn't a possibility with this case, unfortunately.

Answer 1

The obvious and silly approach is to put a battery in each half of the design and communicate wirelessly...

This is called a "clamshell enclosure" and there are two basic practices for routing wiring through the hinge. The first, you alluded to, use cabling bundled into a minimum cross-section (round bundle) and route through the actual hinging mechanics. The other is to use Flexible Flat Cable (FFC/FPC).

Numerous mass produced cable systems for this exist (due to cell phones, monitors, laptops, etc). For starters, you could check out the Hirose FP19 series.

Answer 2

Use the rainbow coloured ribbon cable in a short arc between the halves. A clear plastic sleeve will help to ruggedise it, and an IDC connector on each end lets you replace it in minutes if it wears out (make up two cables!) The design constraints you face on a project like this are different from commercial manufacturers - you can take advantage of this to make maintenance actually easier around vulnerable areas like cables and connectors.

Plus, that ribbon cable looks awesome.

I built one of these in mahogany and brass. It was Z80 based and, unfortunately, was getting obsolete faster than I could finish it!

Answer 3

If a cable or case change is absolutely not an option, then communicating wirelessly is the only option.

To avoid a battery in both halves, I'd think about putting everything in the LCD side, then use a small IR comm link between the keyboard and other half. The power for the keyboard should be minimal, so could be provided via resonant inductive coupling (though the placement and angle of operation depending on the angle of the open case would need careful consideration, but efficiency is probably not so important as long as you keep the keyboard side power consumption down)
It shouldn't be too hard to rig up something to give it a quick test, so you can quickly verify whether it's a viable option.

Or a small solar cell and little rechargeable battery in the keyboard side could be used - solar cell on the outside of the case obviously :-)