Duino Mega v1.0


This sheet shows the documentation for the Duino Mega2560 Rhomb.io Master Module.


The Duino Mega2560 is a certified Rhomb.io Master Module that contains an ATmega 2560 microcontroller, the IC in which the popular Arduino/Genuino Mega board is based. This IC is a low-power CMOS 8-bit microcontroller based on RISC architecture.

The module allows to program the microcontroller by using the Arduino IDE as it were a genuine Arduino/Genuino Mega board. This gives to the user the capability to export easily a project originally made for the Arduino platform and transform it in a modular, tiny, and powerful professional product.

As a Rhomb.io Master Module, the Duino Mega2560 module can be used on any Rhomb.io motherboard that includes the Master Module socket, such as the Phobos or the Zepto boards, for example.

The next two figures show a 3D view from the top and bottom side.

Duino Mega2560 3D view top v2.jpg Duino Mega2560 3D view bottom v2.jpg

Module specifications

As a summary, these are the main features of the Duino Mega2560 Master Module:

Duino Mega2560 module features
Microcontroller ATmega 2560-16CU
Operating voltage 4.5 - 5.5 V [1]
Digital I/O pins 54 (of which 15 can be PWM)
Analog Input pins 16
DC current per I/O pin 20 mA
Flash memory 256 KB (8 KB for bootloader)
Clock speed 16 MHz [1]
User LED 1

As it has been mentioned above, the Duino Mega2560 Master Module contains an ATmega 2560 microcontroller. This 8-bit RISC machine has 54 digital input/output pins (15 of them can be used as 8-bit PWM outputs), 16 analog inputs, 4 UARTs and a 16 MHz quartz crystal. More details can be found at the manufacturer documentation here (ATmega 2560).

The module is ready to use with the Arduino IDE. That is possible because a bootloader has been installed on the ATmega 2560 and the module includes also a USB to UART converter in order to transform the UART signals from the microcontroller to USB signals from the computer, where the IDE is installed. Then, the user only has to plug the Duino Mega2560 module on the master socket that will be found on some of the Rhomb.io motherboards, and connect the USB to a computer. The "Getting started" section shows how to do that using a Rhomb.io Phobos motherboard.

Duino Mega2560 Block Diagram v4.jpg

There are six connectors available on the board: two of them are the standard Rhomb.io connectors for modules, and the remaining ones are auxiliary connectors tied to the Arduino/Genuino Mega standard signals. This gives more flexibility to the module and allows to use the entire pinout available on the microcontroller. On the section "Auxiliar connectors" it has been summarized the signals tied to the four auxiliary connectors.

On the Block Diagram, it is shown that the user has four options for selecting the module power supply: VSYS, 3V3, 2V8_300mA and 1V8_150mA. There is a trace which connects, on the board, VSYS to the module supply (DVCC on the schematics), so the default supply is VSYS. If the user needs to choose another signal, this trace should be cut and a short circuit should be done by soldering the corresponding solder pads. More details regarding the supply capabilities can be found at the documentation for the Rhomb.io standard.

Note that there are three LEDs on board. The red LED blinks when the USB to UART converter uses the TX line, and the orange LED blinks when uses the RX line. The anode of the green LED is connected to the pin 17 on the microcontroller, so it is user programmable.

The following figure identifies the main parts of this Rhomb.io module.

Duino Mega2560 Module Description Top v3.jpg Duino Mega2560 Module Description Bottom v3.jpg



The GPIO signals from the standard Rhomb.io connectors are not used on this module. Nevertheless, all the signals from the microcontroller are tied to the auxiliar connectors. Look at the "Auxiliar connectors" section for more details.

Serial interfaces

The following table indicates the available serial interfaces on the Rhomb.io standard and its been indicated the used ones. The table also shows the nomenclature used on the schematic and its corresponding on the Rhomb.io standard.

Signal (Rhomb.io) Signal (module) Used by Signal (Rhomb.io) Signal (module) Used by
I2C_SDA IO20/SDA Microcontroller SPI_MISO IO50/MISO Microcontroller
UART_RXD UART.RXD See the note[2] USB

The blank fields are unused signals on the module. Note that the I2C pull-ups resistors should be mounted on the bus, otherwise, the I2C will not work. For more details, look at the specifications for the Rhomb.io standard.


The Secure Digital Input Output (SDIO) interfaces are not used on the Duino Mega2560 module.


As per the available supply rails on the board, there is a summary on the next table. Note that it is possible to select the general supply on the module. The default supply is VSYS, but in the case the user may need other voltage, the trace in between the VSYS solder pads should be cut and the desired solder pad should be soldered in order to select the desired supply.

Signal (Rhomb.io) Signal (module) Voltage (V) Used
1V8 150mA DVCC 1.8 Selectable
2V8 150mA DVCC 2.8 Selectable
VCH 5 No
VSYS DVCC 3 - 5.5 Selectable (default)
Buck8 DVCC 3.3 Selectable
Buck9 DVCC 3.3 Selectable

The microcontroller is connected to a 16 MHz crystal. This is the working frequency when the power supply (DVCC) is between 4.5 V and 5.5 V. For lower levels, the clock frequency will be reduced. Note that the maximum voltage value accepted is 5.5 V. More details can be found on the manufacturer documentation here (ATmega 2560). It is also recommended read the Rhomb.io standard specifications.

Other signals

The CLK_32KH, AD_OUT and PWM_INT signals are not used on the Duino Mega2560 Master Module. More information regarding these signals can be found at the specifications for the Rhomb.io standard.

Auxiliar connectors

On the following table it is shown the signals that have been interconnected from the microcontroller to the auxiliary connectors. Note that all the Arduino/Genuino MEGA signals from the ATmega 2560 are tied to the connector, so any signal could be extracted from the board as it were the headers on a genuine Arduino/Duino board. Look at the Arduino/Genuino MEGA documentation for more details here (Arduino/Genuino MEGA).

Connectors J3 and J5 Connectors J4 and J6
Pin Signal name Pin Signal name Pin Signal name Pin Signal name
1 IO0/RXD0 26 IO37 1 RESET 26 AD15
2 IO1/TXD0 27 IO36 2 AD5/TMS 27 AD14
3 IO2 28 IO35 3 AD4/TCK 28 AD13
4 IO3 29 IO34 4 AD6/TDO 29 AD12
5 IO4 30 IO33 5 AD7/TDI 30 AD11
6 IO5 31 IO32 6 31 AD10
7 IO6 32 IO31 7 32 AD9
8 IO7 33 IO30 8 33 AD8
9 GND 34 IO29 9 34 GND
10 IO8 35 IO28 10 35 AD7/TDI
11 IO9 36 IO27 11 IO51/MOSI 36 AD6/TDO
12 IO10 37 IO26 12 IO52/SCK 37 GND
13 IO11 38 IO25 13 IO53/SS 38 IO50/MISO
14 IO12 39 IO24 14 39 IO49
15 IO13 40 IO23 15 40 IO48
16 AREF 41 IO22 16 41 IO47
17 IO20/SDA 42 GND 17 42 IO46
18 IO21/SCL 43 IO14/TXD3 18 43 IO45
19 GND 44 IO15/RXD3 19 GND 44 IO44
20 DVCC 45 IO16/TXD2 20 AD0 45 IO43
21 DVCC 46 IO17/RXD2 21 AD1 46 IO42
22 DVCC 47 IO18/TXD1 22 AD2 47 IO41
23 IO51/MOSI 48 IO19/RXD1 23 AD3 48 IO40
24 IO50/MISO 49 IO20/SDA 24 AD4/TCK 49 IO39
25 IO52/SCK 50 IO21/SCL 25 AD5/TMS 50 IO38


Click the image below to download the schematic files.

Bill of materials

Click the image below to download the BOM files.

Fabrication files

Click the image below to download the fabrication files.

Mechanical specifications

Duino Mega2560 Module Dimensions v1.JPG


  • Precaution against Electrostatic Discharge. When handling Rhomb.io 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.io 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 the Rhomb.io 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: info@rhomb.io

Where to buy

You can purchase this item at the Rhomb website store.

Please, click the icon below.

  1. 1.0 1.1 For working at 16 MHz, the supply should be in between 4.5 V and 5.5 V. When the power supply is below 4.5 V, the clock speed decreases
  2. By default, the UART_RXD and UART_TXD signals are not connected to the Rhomb.io standard connectors. It is possible connect those signals by assembling the resistors R2 and R3. Please, look at the schematics