Embedded Open Modular Architecture/EOMA-200

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  • Target uses: Mass-volume retail products. Examples: Small Desktop systems, Micro servers, Smart NAS Home Servers, Digital Signage, Industrial PCs, Education and R&D purposes.
  • Dimensions: 100mm x 65mm PCB in a 103 x 68 x 16mm case
  • Pinouts: 4 50-pin B2B connectors providing 200 mandatory pins
  • Extensibility: 30mm x 14mm front-facing panel space and 2nd 65mm x 14mm front-facing panel
  • Power provision: 5V @ 3.5A and 3.3V @ 3.5A (29 Watts total)


With many standards providing 200 or more pins, the differentiator which makes EOMA-200 worthwhile is that all other standards are bare PCB factory-only modules with optional sizes and optional functions. These factors combine to make other standards realistically installable only by experts or technical engineers with knowledge of ESD precautions and the full details of the available options.

The EOMA-200 modular standard is designed to be user-installable in mass-volume appliances. There are no options on the pinouts, thus making the purchasing decisions and the installation easy for the average person. Instead, options for extensibility are offered via two front-facing panels, in exactly the same way that standard ITX and ATX motherboards provide a standard front-facing area. One is of size 30mm x 14mm, and the other is of size 65mm x 14mm. The 65mm panel is sufficient to fit up to 4 Ethernet ports, or up to 8 USB2/3 ports, an HDMI connector, eSATA etc. The 30mm panel is intended but not limited to having an on-board MiniPCIe slot behind it, such that WIFI SMA connectors can be put into the 30mm panel.

Preliminary pinouts

Total pinouts summary

These pinouts are NOT OPTIONAL. However, within the majority of the interfaces is the ability to down-level negotiate or provide less than the full set of functionality. For example: if a particular SoC or CPU does not have USB3, then the USB3 pins can be left out and USB2 only provided. Likewise for PCIe: if a particular SoC or CPU does not have full 4-lane PCI Express capability then a 2x or even a 1x lane can be provided. Likewise also for the SD/MMC which can reduce down as far as 4 pins (in SPI mode); I2S as well can reduce down to 5 pins; Ethernet can down-level negotiate to 100mb/sec or even 10mb/sec.

HDMI: 12
USB3 1: 6
USB3 2: 6
USB3 3: 6
USB2 4: 2
USB-OTG 4: 3
I2C 0: 2
I2C 1: 2
I2S: 8
5V : 8
3.3V : 6
GND: 21
SDMMC 1: 12
SDMMC 2: 12
SPI: 4
PCIe4x: 20
Gig Eth: 8
GPIO: 24
UART 1: 2
UART 2: 4
Total: 200


  • PCI Express pinouts: [1]
  • SD/MMC description of 4-pin SPI mode: [2]
  • HDMI (Type A) pinouts: [3]
  • SD/MMC: [4]
  • SD/MMC 1-bit, 4-bit and 8-bit modes: [5]
  • eMMC: [6]
  • eMMC pinouts: CMD, CLK, RST, D0-D7. 1 extra pin reserved for Card Detect (if needed)

Connector 1

This block contains HDMI, Ethernet, I2S, I2C, SPI, 8-bit SD/MMC and 6 GPIO. HDMI also has 5 additional GND pins, bringing the total GND pins to 9 for this connector. It also has 3 power pins (2 5V and 1 3.3V)

1-12: HDMI
13: GND
14-21: Gig Eth
22: GND
23-34: SDMMC 0 (8-bit)
35-38: SPI
39-40: I2C 1
41: GND
42-43: 2 5V
44: GND
45-50: 6 GPIO


  • HDMI signals (Type A): Data2+, Data2-, Data1+, Data1-, Data0+, Data0-, Clock+, Clock-, CEC, SCL, SDA, HPD

Connector 2

This connector is primarily for PCI Express. 4 of the 6 GPIOs are dedicated to PCI Express management, and the I2C lane is also intended for connection to the PCI Express bus. Also provided is SD/MMC. There are 6 GND pins in total on this connector, and 4 3.3v power pins.

1-24: PCIe4x + 4 GND
25-26: I2C 0
27-38: SDMMC 1 (8-bit)
39: GND
40-43: 4 3.3V
44: GND


  • PCI-Express optional JTAG is for debugging of PCI-e cards, not for the provision of JTAG to debug the Host CPU. If JTAG is to be provided, it is recommended that either some of the GPIO pins be connected to the PCI Express lanes (and use bit-level emulation of JTAG on the Host CPU), or that an Embedded Controller (such as an STM32F) be dedicated to this (and other) purposes, or an alternative interface (such as USB or I2C) have a converter IC added which can be used.

Connector 3

This connector provides 24-pin RGB/TTL, SATA, 2 UARTs and 6 GPIO pins. It also has 4 GND pins and 2 5V power lines. UART 1 is a 2-pin RS232, whilst UART2 provides TX, RX as well as CTS and RTS.

1-28: RGB/TTL
29: GND
30-33: SATA
34: GND
35-38: UART 2
39-40: UART 1
41: GND
42-43: 2 5.0V
44: GND
45-50: 6 GPIO

Connector 4

This connector is primarily for USB, although it also provides an 8-bit I2S and 6 GPIO pins. There are also 7 GND pins in total and 3 5V power lines.

1-7: 1 USB3 + 1 GND
8-14: 2 USB3 + 1 GND
15-21: 3 USB3 + 1 GND
22-24: 4 USB2 + 1 GND
25-28: 5 USB-OTG (Tx, Rx, ID) + 1 GND
29-36: I2S
37: GND
38-41: 4 5V
42: GND
45-50: 6 GPIO


  • USB3 pinouts [7]
  • I2S 8 pins: MCLK, BCLK, LRCK, DO0, DO1, DO2, DO3, DI

Example EOMA-200 PC

The example below shows how a small Desktop PC can be created. This example has:

  • HDMI output
  • 1 USB3
  • 4 USB2
  • 2 Gigabit Ethernet
  • 1 eSATA
  • SD/MMC
  • Micro-SD
  • Micro-USB
  • Mini PCIe with a combined Bluetooth 4 and 802.11N 300mb/sec WIFI card
  • Standard Audio connectors
  • DC Power input jack