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Gta01b v3 case back open white.jpg

This is the current back, showing where the battery plugs in (central) where the SIM plugs in (middle, lower) and the microSD socket, which is under the SIM socket.

The USB socket is approximately a centimetre to the right of the edge of the void the battery fits in.

The standard back fits snugly to the phone, meaning there is no spare space.

An altered back, that is 5mm or so deeper offers many possibilities, without modifying the core phone at all, and offering users more choices.

Ideas that do not require any modification of the phone.

  • Larger battery, perhaps doubling the existing capacity.
  • A flex cable from the microSD slot, to a full-size SD socket on the right-middle of the edge of the back of the phone (top right on the image).
  • A flex cable from the SIM slot, to a double SIM socket on the left-middle of the phone (bottom right on image).
  • Stylus holder
  • AA or AAA battery power options.

Ideas which require slight modifications of the phone.

  • Alter the plastics moulding so that the back of the USB socket is accessible, and somehow make a flex cable connectable there.
    • Add a USB blanking plug, to blank off the USB port when the expansion back is in use. This brings USB up into the back of the phone.

This adds many possibilities. Add a small 3.6-5V converter, and if it's possible to switch on the voltage status of the D0/D1 lines, to turn these off, and add a USB 1.1 hub chip, this makes for a very, very hackable back.

Add AA or AAA battery holders, to run or charge from.

  • Extra SD cards via USB.
  • USB-PIO chip - one of many, to give drive for as many LEDs as you want scattered over the back.
  • USB wlan key, with the cover ripped off, and the connector removed and soldered straight onto the hub outputs.
  • Large contacts on the back, to enable a simple dock, that it just drops into and charges, with static protected USB slave mode port that.
  • IRDA, to enable IR keyboards to work.

With a slightly thicker back, and much more complex mechanics, a slide-out keyboard - for use in landscape mode - would be possible. A camera would also be an interesting option.

The advantage of the first class of devices is that they requires no engineering on the behalf of FIC, everything is external, and yet the case can be easily swapped by users.

The second type, with USB requires another socket on the board, and some plastics changes, or a much more involved install suitable only for a very few users.

There are many possible special or general purpose backs possible.

Some basic ideas:

  • powered USB hub: 4 AA battery slots, 4 USB sockets
  • camera: 4 AA battery slots, camera, external SD slot
  • business: 4 AA battery slots, slide out keyboard, wifi

What FIC could do.

On slightly deeper modifications, one or two GPIO pins brought out to a connector would be ideal. Perhaps a connector next to the USB port, with connections for all the USB pins, 2 GPIO, battery VCC.

This would be a one-time plug in to the connector by the user. The cable would then be taped or glued onto the case, to provide strain relief in case the user opens the case without care.