This sheet shows the documentation for the Gaia rhomb board. Preliminary version, use only for data updating or corrections.


The Gaia board is the perfect tool designed for helping you to bring to the market your ideas and transform them in real products. This board helps you to explore the rhomb modular hardware platform and to discover all its capabilities by bringing direct access to the more than 300 signals that conforms the standard rhomb cores. This board is the only tool that you need if you want to speed up your product design, test and validation stages.

The next figure show a 3D view for the Gaia board.

Gaia 3D Top v2.JPG Gaia 3D Bottom v2.JPG

As a summary, the following table indicates the main features:

Gaia features
rhomb Core All the core signals available
rhomb Modules 1 x slot
USB 4 x USB type A 2.0
2 x USB type B (only power)
SD Micro SD card reader
Ethernet 10BASE-T and 100BASE-TX
Power supply Battery or USB
J-TAG ARM-20 J-TAG Header


  • Testing
  • Mini-PC
  • Media center
  • IoT
  • NAS
  • Education

Board specifications

Key features

The Gaia board has been designed to help you to convert your hardware and firmware projects on a product by using the rhomb modular platform. It gives access to more than 300 signals, all these coming from the rhomb cores, so this board is perfect not only for design, but for test and validate your products. But it is not limited only to that, it also includes a socket for standard rhomb modules, and offers a wide range of connectivity through USB, Ethernet, HDM, etc.

Check out the Block Diagram to understand what is under this PCB. Note that the power supply can be provided in two different ways, either by using a battery or by using directly a standard USB power source. This board also includes a J-TAG port, and 8 LEDs for giving feedback and to help on the product developing stage.

Gaia BlockDiagram v2.JPG

The following figures identify the main parts of the board. The most important parts will be explained with more detail in the next sections.

Gaia Description Top v3.jpg

rhomb Core

The Central Processing Unit (CPU), RAM, PMIC among other auxiliary elements are embedded on the core, a small standardized board designed to be connected on the core socket. Look on the description image to see where this socket is placed. On the following link you can find the currently available rhomb cores. [Add link to the store, cores section]

Core Exynos v2.jpg Core AMD v1.jpg

rhomb modules

Lots of rhomb modules focused in different areas such as communications, sensing or storage, are available. The Gaia board allows to connect one standard rhomb module. The description image on the "Key features" section shows where is placed the module socket to connect it. Look at here [Add link to the store, modules section] to chose the desired module in order to test it or to expand the capabilities of the Gaia board.

Modules v2.jpg


Two memory options are available for the Gaia board: a micro SD card and the rhomb Memory eMMCXX Module (Add link to the store). The eMMC memory modules used to be faster than the SD cards, but it occupies one module socket. The user should choose either one or other. In order to allow that, there is a switch array on the board that should be configured as it is shown on the two following images:

  • eMMC bootloader configuration:

Bootloader eMMC v1.JPG

  • Micro SD card bootloader configuration:

Bootloader uSD v1.JPG

The DIP switches should not be moved unless the system is turned off.

Gaia Memory v4.jpg


The Gaia board has 4 USB 2.0 type A ports, all of them working as host. It includes also a micro USB type B connector that works as OTG. Note that there are two more micro USB type B connectors placed at the right side of the board; those two connectors are only for power purposes. See the "Power" section for more information regarding its functionality.

It is also available an Ethernet port that can carry traffic at the nominal rate of 100Mbit/s, supporting full and half-duplex with flow control. Look at the image below to identify each connector on the board.

Gaia Connectivity v4.jpg


The Gaia board is fully compliant with the HDMI audio and video interface. The next figure shows where the HDMI type A connector is placed on the board.

Gaia VideoAudio v2.jpg

Switch, Buttons and LEDs

The Switch ON is used to cut the power input. When the switch is ON, connects VSYS* with VSYS. When the Power Management Integrated Circuit (PMIC) on the core receives VSYS it is ready to generate all the voltages needed for the entire circuitry. For more details, look at the "Block diagram" and the "Schematics" sections.

The Gaia board also include two buttons: the Button RST and the Button ON. The first one resets the PMIC and, consequently the system. The second is used to turn on the PMIC and the processor.

A total of 8 LEDs are assembled on the Gaia board in order to give status feedback to the user. The functionality of each one of them is explained on the following table:

LED Description
LDO03 ON Turned on when the power supply line named LDO03_1V8_300mA is ready
BUCK8 ON Turned on when the power supply line named BUCK8_3V3_300mA is ready
LDO21 ON Turned on when the power supply line named LDO21_2V8_300mA is ready
VSYS Shines when the main power supply source on the board (VSYS) is working
USR1 LED free to use connected to the GPIO01. By fault configured as heartbeat
USR2 LED free to use connected to the GPIO02. By default indicates memmory activity
USR3 LED free to use connected to the GPIO03. By default indicates CPU activity
USR4 LED free to use connected to the GPIO04. By default indicates LAN activity

The LDO03 ON, BUCK8 ON and LDO21 ON LEDs are intended to give to the user a feedback about the booting sequence. The LDO03 ON and the LDO21 ON LEDs indicates that the Power Management Integrated Circuit (PMIC) on the core board is ok. These LEDs will be turned on once the Switch ON is on and the Button ON is pressed about two seconds. After a few more seconds, the BUCK8 ON LED will be turned on, meaning that the processor is on the initializing stage. Once this sequence has been done, the three LEDs will be always shining unless the user modify the configuration of the PMIC.

The USR1, USR2, USR3 and USR4 LEDs have been configured as is indicated on the table, but those LEDs are free to use. Force to high level the corresponding GPIO to make the LED shine.

Gaia SwitchLEDsButtons v4.jpg


The Gaia board can be used for designing, testing and validate the product, for this reason the board includes a standard ARM 2x10 pin JTAG connector. In addition to that, it's been provided easy access to the UART1 and UART3 by means of standard 2.54mm headers. As the rhomb standard defines, the UART1 is the interface used for the system debugging. The UART3 can be used according to the user needs.

Gaia Debugging v2.jpg


Core pinout

The Gaia board has been designed for giving to the user a functional and useful tool for product developing and testing, for this reason on this board all the signals providing from the core has been expanded to accessible-size headers in the same order as in the core socket. The following image shows how are interconnected the pinout from the core socket with the expansion headers.

GAIA core pin out v1.jpg

As an example, the pin 16 on the connector J3 is tied to the pin 16 on the header J3_HDR. This pin is used in order to reset the PMIC on the core and, as a result, resets the system. Force the pin 16 to zero on the J3_HDR header to see that the resets happens. Look at the "Schematics" section to identify the mentioned connectors.


The following table summarizes the GPIOs used on the Gaia board. Unless specific indications, all the signals are active high.

GPIO Signal Description GPIO Signal Description
0 21
1 LED_MCU_1 Activates the LED USR1 22
2 LED_MCU_2 Activates the LED USR2 23
3 LED_MCU_3 Activates the LED USR3 24
4 LED_MCU_4 Activates the LED USR4 25
5 26
6 27
7 MOD1_GPIO0 Module 1 socket, GPIO 0 28
8 MOD1_GPIO1 Module 1 socket, GPIO 1 29
9 MOD1_GPIO2 Module 1 socket, GPIO 2 30
10 MOD1_GPIO3 Module 1 socket, GPIO 3 31
11 MOD1_GPIO4 Module 1 socket, GPIO 4 32 MOD1_SLOT When '0', module pluged on the socket 1
12 MOD1_GPIO5 Module 1 socket, GPIO 5 33 MOD1_SPI_CSn SPI chip select for module 1 socket
13 MOD1_GPIO6 Module 1 socket, GPIO 6 34 MOD1_EN Enable the 3V3 source power on the module 1 socket
14 MOD1_GPIO7 Module 1 socket, GPIO 7 35
15 36 ChargMangmnt_!EN Enable the battery charger. Active low
16 37 ChargMangmnt_!POK Power input for the battery charger is ok. Active low
17 38
18 39
19 40
20 41

For more details, look at the specifications for the rhomb standard.


The following table summarizes the signals that can cause interrupts on the core.

XEINT Signal Description XEINT Signal Description
0 MOD1_I2C_INT I2C interrupt on the module 1 8
1 MOD1_SPI_INT SPI interrupt on the module 1 9
2 10
3 11
4 12
5 13 CEC_HDMI HDMI Consumer Electronics Control
6 14
7 HPD_HDMI HDMI hot plug detect 15 XEINT15 System power ON

Serial interfaces

The following tables indicates the use of the available serial interfaces on the rhomb standard. For more details, look at the specifications for the rhomb standard.


I2C Used by
1 Module socket 1
Fuel Gauge

The I2C1 has two pull-up resistors at 4.7kΩ connected to a 3V supply (LDO12_3V0_150mA).


This interface is not used on the Gaia board.


SPI Used by
1 Module socket 1


UART Used by
0 Module socket 1
1 Debug pads
3 Debug pads

As the rhomb standard defines, the UART1 is the interface used for the system debugging. Note that both the UART1 and the UART3 are easily accessible by means of standard 2.54mm headers. The UART3 can be used according to the user needs.


USB Used by
Host_1 Hub USB/Ether host
Host_2 Module socket 1
OTG uUSB-B connector
USB1_HUB2 USB-A connector


The next table shows how the Secure Digital Input Output (SDIO) interfaces are connected on the Gaia board.

SDIO Used by
0 Module 1 socket
2 Micro SD

For more details, look at the specifications for the rhomb standard.


The Block Diagram shows that the power supply could be provided through the two micro USB type B connectors or from a Li-Ion battery. A switching circuit is responsible to drive the current according to the existing power input. The "Main PWR USB" is the main power supply and feeds all the circuitry. The "Secondary PWR USB" is a secondary source power that feeds the four USB type A connectors. This should be used when the devices connected there needs more power than the "Main PWR USB" is capable to supply. Note that the data lines are not connected to the micro USB B connectors, are used only as a power supply connectors.

When the power is supplied trough the USB connector, the power adapter should be able to supply 2A of output current, as a minimum.

Gaia Power v2.jpg

If a battery is used, it should be connected according to the polarity indicated on the board, where the symbol "+" indicates the positive terminal. The system supports only single cell Li-Ion batteries and it will start to charge when a power supply is connected to the "Main PWR USB" USB B connector. The charging current is configured as 1A. There is also a fuel gauge IC on the board that is controlled trough the I2C1. Look at the manufacturer documentation (DS2782) to discover the amount of parameters that is capable to measure. When the battery voltage drops under 3.3V, a battery protection circuit cuts the input battery current in order to prevent the deep discharge.

The following table summarizes the power supply signals on the Gaia board and indicates where are used.

Signal Voltage (V) Used by Signal Voltage (V) Used by
VCH 5 Module 1 socket LDO13_1V8_150mA 1.8 Module 1 socket
Battery charger IC LDO14_1V8_150mA 1.8 Pin header
VSYS 3 - 5.5 Core LDO16_1V8_150mA 1.8
HDMI LDO17_1V2_300mA 1.2
Module 1 socket LDO19_1V8_150mA 1.8
LEDs (all) LDO20_1V8_150mA 1.8
BUCK8_3V3_300mA 3.3 Module 1 socket LDO21_2V8_300mA 2.8 Micro SD
Boot sequence Boot sequence
BUCK9_3V3_300mA 3.3 Module 1 socket LDO22_2V8_300mA 2.8 Module 1 socket
LDO04_2V8_150mA 2.8 LDO23_3V0_300mA 3 Hub USB/Ethernet
LDO05_1V8_150mA 1.8 HDMI LDO24_3V0_150mA 3
LDO09_1V8_150mA 1.8 LDO25_3V0_150mA 3
LDO10_1V8_300mA 1.8 LDO26_3V0_150mA 3
LDO11_1V8_150mA 1.8

For more details, look at the specifications for the rhomb standard.

Secondary signals

On the following table it is shown how the Analog to Digital, PWM and CLK signals are connected on the Gaia board.

Signal Used by
Analog to Digital
AD_IN0 Module socket 1
PWM_OUT0 Module socket 1
CLK 32.768kHz
CLK_32KH Module socket 1

For more details regarding these signals, look at the specifications for the rhomb standard.

Getting started

Look at this link


The schematics are available here (Gaia Schematics v1).

Bill of materials

[Add link]

Part number package marking

Mechanical specifications


Gaia Dimensions v1.JPG




  • Precaution against Electrostatic Discharge. When handling rhom products, ensure that the environment is protected against static electricity. Follow the next recommendations:
  1. The users should wear anti-static clothing and use earth band when manipulating the device.
  2. All objects that come in direct contact with devices should be made of materials that do not produce static electricity that would cause damage.
  3. Equipment and work table must be earthed.
  4. Ionizer is recommended to remove electron charge.
  • Contamination. Be sure to use semiconductor products in the environment that may not be exposed to dust or dirt adhesion.
  • Temperature/Humidity. Semiconductor devices are sensitive to environment temperature and humidity. High temperature or humidity may deteriorate semiconductor devices characteristics. Therefore avoid storage or usage in such conditions.
  • Mechanical Shock. Care should be exercised not to apply excessive mechanical shock or force on the connectors and semiconductors devices.
  • Chemical. Do not expose semiconductor device to chemical because reaction to chemical may cause deterioration of device characteristics.
  • Light Protection. In case of non-EMC (Epoxy Molding Compound) package, do not expose semiconductor IC to strong light. It may cause devices malfunction. Some special products which utilize the light or have security function are excepted from this specification.
  • Radioactive, Cosmic and X-ray. Semiconductor devices can be influenced by radioactive, cosmic ray or X-ray. Radioactive, cosmic and X-ray may cause soft error during device operation. Therefore semiconductor devices must be shielded under environment that may be exposed to radioactive, cosmic ray or X-ray.
  • EMS (Electromagnetic Susceptibility). Note that semiconductor devices characteristics may be affected by strong electromagnetic waves or magnetic field during operation.


rhomb reserves the right to make corrections, enhancements, improvements and other changes to its products and services, and to discontinue any product or service. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All the hardware products are sold subject to rhomb terms and conditions of sale supplied at the time of order acknowledgment.

All brand names, trademarks and registered trademarks belong to their respective owners.

We are constantly striving to improve the quality of our technical notes. If you find an error or omission please let us know. Email us at: .