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Openmoko WikiReader

The  Openmoko  Wikireader  twitter stream had a link off to the github repository at  http://github.com/wikireader. Poking around showed some interesting things:

  • The device is quite simple. No operating system, only the main application running directly on the hardware
  • The CPU is a Epson  S1C33E07 (pdf) which is part of the  S1C33 family
  • There's a version of  Forth for the device written by Christopher Hall
  • The closest thing to a kernel is a library called 'mahatma'
  • Python is their glue language of choice. Yay :)
  • The Wikipedia image is compressed using lzma

I'm mostly interested in the hardware and other things it can be used for. Epson say that the CPU is appropriate for 'middle-low range electronic dictionaries and label writers/printers' so it would be really interesting to know how much it costs in volume.

The board has a EOREX  EM48AM1684VTD-75F 16M x 16 SDRAM (32 MB) and some type of SPI based flash. The datasheet says:

  • Runs up to 60 MHz
  • 32 bit Epson specific RISC core. 16 bit instructions a'la THUMB
  • USB 2.0 full speed device
  • 22 k of internal RAM
  • 90 MHz SDRAM controller
  • Timer/counter/PWM, WDT, ADC, GPIO
  • SmartMedia?
  • SPI, I2C, I2S
  • LCD - mostly 8 bit low resolution though

The power consumption is quite good - 19 mA at 48 MHz for the core plus another 20 for the basic peripherals. Halt is 3 mA and Sleep is 1 uA - sleep means that the SDRAM is turned off though.

It can boot of a range off the usual things: SPI, NOR flash, and NAND. It's not obvious what debug support the chip has.

Teardown

This isn't much of a teardown but it's a nice, searchable term unlike 'open the WikiReader case'.

The case is secured by two screws in the battery compartment. There are three plastic latches on each side and two deep latches on the bottom edge. There are four posts, one in each corner. The case holds together very well and requires a fair amount of force to separate. Do each side first, then fold it open.

Click on the images for a full size version

Some of the chips are:

There's a surprising number of passives on the board. I've got serial number 103412. I'd guess the 10 is a prefix.

There's a few missing connectors that might be interesting:

  • JP1701 in the top left is for a battery connector
  • CON1503 on the bottom right is next to a set of debug test points but doesn't seem to be connected. Could be for a JTAG style connector
  • CON1504 on the bottom left next to the SDRAM. Might be for buttons
  • CON1505 is next to the cable off to the LCD
  • Test points to the right of the CPU marked DEBUG2, DEBUG3, DEBUG4, GPIO1, GPIO2, and GPIO3

The CPU has a RTC but I can't see a 32 kHz crystal. Then again, I can't see the main crystal either - Q1501 might be a ceramic resonator.

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