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A51
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Innards
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A51 - Innards
Board Set
The electronics package for this device consists of a mainboard/display controller and a single board computer, plus an auxillary button board with 4 microswitches.

Main Board/Display Controller
The main board has the following features:

  • Header for Gumstix single board computer
  • 10 pin FPC connector with serial I/F for Gumstix and JTAG for display controller CPLD
  • 10 pin FPC connector for button board I/F
  • 2 series cell Li-ion/Li-polymer switching charger
  • Auto input power source selection (via LTC4412)
  • Low battery detect circuit
  • Battery disconnect switch
  • Power management/conversion circuits
A Metrnonome 834 display controller is also implemented on the board. This display controller is centered on a Xilinx CPLD and also includes bias voltage generation and common plane driving circuits.

Single Board Computer
The single board computer used is the Gumstix 400f-bt, available from Gumstix, Inc. This board is very compact, affordable, and packed with features:

  • 400MHz Xscale running Linux
  • MMC card slot
  • Bluetooth, USB, and serial interfaces
  • Enough flash and RAM to do the job
  • Excellent community support and documentation

Button Board
A very simple board with 4 switches mounted, which eventually end up with laser cut acrylic buttons glued on top of them. Interfaces to the main board using a 10 pin 0.5mm flat cable.

Batteries
In these photos, 4 550maH Li-polymer batteries from Kokam are used. They are connected as 2 double series cell stacks in parallel. A good source of low volume polymer cells is the RC plane industry. I think I got these from a dealer in Canada. Unfortunately Kokam discontinued this cell, so I have moved to some cells from Varta Microbattery.

Display
A5 TFT Electronic paper display, as an engineering sample from E Ink. Because the display is so large and the case so thin, I backed up the glass TFT with a 0.5mm sheet of titanium, which is the gray metal visable in the photo below.

Design partially original and partially ripped off from other websites
by Holly Gates