Portable Linux Based Audio Player Core Board based on Freescale IMX233

Processor:
	Freescale MCIMX233CAG4B ARM9 Integrated System on Chip

Memory:
	Micron MT46V32M16P-75L DDR1 64MB 16-bit wide

Firmware Media:
	Micro Secure Digital
	I2C EEPROM for internal bootrom patch

Application Media:
	Micro Secure Digital (core board)
	Secure Digital (User Interface Board)

External Interface:
	USB mini-B target, Power and Data

Internal Expansion:
	50 conductor board/board connector, 0.65mm pitch

Audio:
	3.5mm Stereo Headphone Jack, 16-ohm Load

LCD:
	128x64 Graphic Monochrome Display, Transreflective, Low Power,
	White LED Backlight

Input:
	4/5 Direction UI Navigation, Tact Switch x4, Rotary Encoder,
	Power Switch

Power:
	Li-Ion battery 1800mAH; USB bus power

Debug Interface:
	JTAG, Debug UART, I2C Bus, SSP1 (1/4 Wire Firmware SD, Ethernet)
	14-pin connector

PC Boards:
	Stacked set of two boards, each 0.5~1.0mm thick,
		40x56.8mm 4 layers (core),
		40x56.8mm 2 layers (User Interface).
	Design Rules: trace/space 6/6mil, via ring/finished hole 24/10mil,

This board set supports a full functionality Linux Based
Portable Audio Decoder.

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0.02 Design Revised and Expanded, Added User Interface Board

Notes and Rationale:

- Added User Interface Board providing Graphic LCD Display,
  input Navigation/Switch/Rotary Encoder, full-size SD connector,
  side located power switch.

- Added second micro SD to core board for application use.

- Delete provision for SPI EEPROM (limited to 2^24 bytes and redundant
  with I2C internal bootrom patch EEPROM).

- Moved I2C EEPROM to core board bottom with the expectation it
  is essentially an interim bandaid.

- Move Hirose 50-pin expansion connector to core board front allowing
  more space-optimized nesting relative to user interface board,

- Replace thru-hole USB B with SMT version.

- Replace 3.5mm audio jack with shorter footprint version

- PCA95[35]x I2C port added to support input devices on user interface board.

- Added debug connector for JTAG/SPI/I2C/SD(programming)/UART/Ethernet
  support.  Also doubles as limited user interface for single (core) board
  embedded use.

- LCD Display is COG with flex interconnect, direct solder to interface board.
  Transreflective display chosen over transmissive to minimize power
  consumption.  External backlight requires diffusing lens.

- Delete DC block electrolytics in headphone circuit.  Too large for
  available board area.  Possible to relocate same to user interface
  board perhaps in the form of audio grade tantalum capacitors.

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0.01 Preliminary snapshot of schematic and board design

TODO:
	Layout debug connector
	Decide use of SPI Flash
	Determine exact connector footprint and stay-out for 1.25mm connectors
	DC block for HP out(?)
	Change from TH to SMD USB-B connector
	Fix connector pin numbering

MISC:
	LCD system mode drive appears to be missing "E" clock for 68xx mode