vertical space (was Re: 3D Scanning)

Werner Almesberger werner at
Wed Jul 14 17:23:24 EDT 2010

Carlos Camargo wrote:
> If we move the processor, (ram+nand) +
> LCD's back-light circuit to the same board we can design a lot of different
> "keyboard pcbs" using a two layer PCB. So, we can provide some special
> signals in the flexible tape (20 lines in BEN).

So far, so good.

> Mandatoty signals: GND, VCC,
> usb (2) SD(7) Audio(6) keyboard (16)

Even if the whole power/charging circuit lives in the bottom shell,
don't you also need some control signals, plus +VBUS for ADIN0 ?

USB also needs USBDET, plus, when adding USB host, another pair of
D+/D-. By the way, how would USB host be supplied with power ? How
have you done it in SAKC ?

Perhaps the keyboard's voracity could be contained a little by
adding some multiplexer or even an MCU dedicated to just keyboard

The current on VCC and GND may also be too large for that FPC,
requiring either multiple traces, or an additional FPC/cable.

That's already quite a lot of stuff and it doesn't even include
the signals we'd want to run to the new peripherals we'd want to
be able to add :-(

If Wolfgang can get the new CPU in an MCP with stacked RAM and
(evil) NAND, the routing should also get a bit easier.

> With this architecture the "main"bord is the LCD board and the daughter card
> will be the keyboard pcb, so if any want to design a different application
> just need to make one cheap card.

Being able to modify the keyboard would be very interesting
indeed. Even better if you get to play with the whole board
underneath too. Metal domes of the right kind seem to be
available to the public, e.g.,

One problem would be that the MicroSD holder probably still has
to go under the keyboard. (Unless you move it into the LCM shell
as well.)

- Werner

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