Embedded Open Modular Architecture/EOMA68/MiniEngineeringBoard

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Micro Board: Engineering, Engineering and Experimentation

This board's primary purpose is to provide a wide range of options for experimentation purposes, as well as an Open Platform for Free Software Development. It therefore includes a low-cost on-board ARM Cortex M3 Embedded Controller. A secondary purpose is for the Micro Board to make the development process of in-house designs a smoother and easier prospect.

The STM32F appears to be the best choice, for exactly the same reasons that Olimex chose the STM32F for their Olimexino. In large volume, the STM32F103RBT6 is around $USD 1.00 to 1.50, making it highly cost effective. Alternative Embedded Controllers (for example those from Texas Instruments) are both slower as well as more expensive.

The Micro Board can therefore be used for several purposes, in combination with the PCMCIA CPU Card:

  • SoC Vendor's "Board Support Package" (BSP) Reference Designs
  • A Free Software Developer Board, similar to the Beagleboard and Pandaboard
  • As a stand-alone Board (without the PCMCIA CPU Card)
  • An Arduino-like replacement, with or without a PCMCIA CPU Card
  • A development platform for ODMs
  • A RepRap 3D Printer controller with or without an embedded network-capable CPU Card
  • An OEM off-the-shelf platform for deployment in Industrial Embedded use.

as well as many other alternative purposes, besides these listed here. For examples of potential combined uses of the Micro Engineering Board, it is worthwhile examining these lists:

The Micro Engineering Board therefore brings together two powerful and flexible concepts into one, to create something that is even more flexible, due to conformance to a simple yet future-proof standard (EOMA/PCMCIA).

Components and Interfaces

Stm32 mini engineering board.png

The Mini-Board's Interfaces comprise:

  • EOMA-compliant PCMCIA Connector
  • eSATA
  • RJ45 for 10/100 Ethernet
  • 2x USB2
  • 5V Power Socket
  • Expansion Header for access to the STM32F's features
  • Expansion Header for pass-through access to 24-pin RGB/TTL, I2C and GPIO from the PCMCIA CPU Card

The ICs required include:

  • a 4-port USB Hub, connecting the PCMCIA CPU Card and the STM32F
  • an STM32F103RBT6
  • a 250mA 3.3v LDO (to supply the STM32F)
  • a small low-speed, low-cost I2C EEPROM.

Total cost of parts is estimated, for mass-volume supply, to be around $USD 5 to 6: the STM32F is approx $1 to $1.50; a GL850G is around $1 to $1.50; the EEPROM around $0.25; a 3.3v 250mA LDO around $0.30. Perhaps the most expensive part is the PCMCIA Connector (MOQ 1k units, example pricing $1.90 from Digikey, FCI P/N 61127. However, if Taobao pricing for PCMCIA headers is anything to go by, prices outside of S.E. Asia for components, such as from Digikey, Mouser and Farnell, are definitely not a good guideline to judge mass-volume mass-production costs.

Smaller Example Board

Mini pcmcia engineering board.png

This example board is much simpler and would be even lower-cost than the version above, comprising nothing more than connectors, effectively. It is included here to show the sort of size that an embedded board would be, in comparison to a Pandaboard (4.5" x 4.0" - 114.3 mm x 101.6 mm). By contrast, the total size of the PCMCIA CPU card with associated minimalist engineering board could well be under 2.25" x 4.25" (56mm x 107mm) - just over half the size of a PandaBoard.

Whilst there are less features shown on the minimalist Engineering Board, it has to be remembered that there can be Expansion Headers on the PCMCIA CPU Card itself (obviously hidden and inaccessible to end-users if the PCMCIA cover is in place). Thus, whilst at first glance it may appear that this minimalist Engineering Board is unsuitable for general-purpose Engineering, it actually depends on the PCMCIA CPU Card on a card-by-card basis. This minimalist option is presented therefore for cases where the interfaces presented through the re-use of the 68-pin PCMCIA connector are sufficient: the Mini Engineering Board is presented as an example for when standardisation is required for Embedded and Industrial Purposes, yet the flexibility of future upgrades of the main CPU card are still also desired.