Mobillyo an Arduino compatible board


The Mobillyo is an Arduino compatible board with an integrated nrf52 BLE, a 1500mAh Li-Ion Battery, a USB HID and solar panel interface.

It is ideal for mobile projects requiring battery power and solar charging.

As an Arduino compatible product, the Mobillyo is a microcontroller board based on the ATmega32u4 (datasheet) and compatible with the Arduino IDE. It has 18 digital input/output pins (of which 6 can be used as PWM outputs and 12 as analog inputs), a 8 MHz crystal oscillator, a micro USB connection, a solar panel jack, a 1500mAh Li-ion Battery, a nrf52 BLE, two ICSP headers, one for the ATega32U4 and one for the nrf52, Tx and RX LEDs connected to the nrf52. It contains everything needed to support the microcontroller wirelessly, free from a physical computer connection; simply connect it to solar panel to recharge the battery.

The Mobillyo differs from other Arduino boards in that it can be used for mobile applications like robots or data gathering applications, eliminating the need for a connection to a power source or computer. The BLE allows the Mobillyo to connect to iPhones or tablets and provides an array of user interface possibilities. The iPhone App includes 4 virtual LEDs, 4 push Buttons, 4 slide switches, 4 sliders and a text area for messaging. The nrf52 serial port is broken out on digital pins 2 and 3.

Microcontroller ATmega32u4
Operating Voltage 3.3V
Input Solar Panel Voltage 5-6V
Battery Capacity 1500 mAh
Digital I/O Pins 18
PWM Channels 6
Analog Input Channels 12
DC Current per I/O Pin 40 mA
DC Current for 3.3V Pin 50 mA
Flash Memory 32 KB (ATmega32u4) of which 4 KB used by bootloader
SRAM 2.5 KB (ATmega32u4)
EEPROM 1 KB (ATmega32u4)
Clock Speed 8 MHz
Lenght 68.6 mm
Width 53.3 mm
Weight 50 g
Bluetooth nrf52
Bluetooth protocol Serial data over Bluetooth with proprietary protocol

The Mobillyo is open-source hardware! The schematic and Kicad files will be published after the official launch.


The Mobillyo can be powered via the micro USB connection or with an external solar panel. The power sources combine to charge the battery.

The solar panel connector is a 2mm JST.
The header power pins are as follows:

  • VIN: Not connected.
  • 5V: Battery output. The voltage at this point will vary between 4.6V and the battery voltage depending on the state of charge of the battery. Les than 50mA should be drawn from this pin. A Schottky diode and fuse protect the battery from reverse power or a short circuit.
  • 3V3. A 3.3 volt supply generated by the on-board switching buck-boost regulator. Maximum current draw is 50 mA.
  • GND. Ground pins.
  • IOREF. The voltage at which the i/o pins of the board are operating (i.e. VCC for the board). This is 3.3V on the Mobillyo.


The ATmega32u4 has 32 KB (with 4 KB used for the bootloader). It also has 2.5 KB of SRAM and 1 KB of EEPROM (which can be read and written with the EEPROM library).

Input and Output

Each of the 18 digital i/o pins on the Mobillyo can be used as an input or output, using pinMode()digitalWrite(), and digitalRead() functions. They operate at 3.3V volts. Each pin can provide or receive a maximum of 40 mA and has an internal pull-up resistor (disconnected by default) of 20-50 kOhms. In addition, some pins have specialized functions:

  • Serial: 0 (RX) and 1 (TX). Used to receive (RX) and transmit (TX) TTL serial data using the ATmega32U4 hardware serial capability. Note that on the Mobillyo, the Serial class refers to USB (CDC) communication; for TTL serial on pins 0 and 1, use the Serial1 class.
  • TWI: 2 (SDA) and 3 (SCL). Support TWI communication using the Wire library. The nrf52 is connected to these pins and respond to address 86 (decimal).
  • External Interrupts: 3 (interrupt 0), 2 (interrupt 1), 0 (interrupt 2), 1 (interrupt 3) and 7 (interrupt 4). These pins can be configured to trigger an interrupt on a low value, a rising or falling edge, or a change in value. See the attachInterrupt() function for details.
  • PWM: 3, 5, 6, 9, 10, 11, and 13. Provide 8-bit PWM output with the analogWrite() function.
  • SPI: on the ICSP header. These pins support SPI communication using the SPI library. Note that the SPI pins are not connected to any of the digital I/O pins as they are on the Uno, They are only available on the ICSP connector. This means that if you have a shield that uses SPI the shield will not work. The ICSP connector is moved to the center of the board to make room for the nrf52 BLE.
  • LED: 13. There is a built-in LED connected to digital pin 13. When the pin is HIGH value, the LED is on, when the pin is LOW, it’s off.
  • Analog Inputs: A0-A5, A6 – A11 (on digital pins 4, 6, 8, 9, 10, and 12). The Mobillyo has 12 analog inputs, labeled A0 through A11, all of which can also be used as digital i/o. Pins A0-A5 appear in the same locations as on the Uno; inputs A6-A11 are on digital i/o pins 4, 6, 8, 9, 10, and 12 respectively. Each analog input provide 10 bits of resolution (i.e. 1024 different values). By default the analog inputs measure from ground to 3.3 volts;  it is not possible to change the upper end of their range using the AREF pin and the analogReference() function.
  • nrf52 BLE TX and RX. These pins are used for data to and from the nrf52.

There are a couple of other pins on the board:

  • AREF. Reference voltage for the analog inputs. Used with analogReference().
  • Reset. Bring this line LOW to reset the microcontroller. Typically used to add a reset button to shields which block the one on the board.

See also the mapping between Arduino pins and ATmega32u4 ports.

  • There are virtual i/o pins, sliders and one text box that can be accessed through the nrf52 BLE. the iPhone App has 4 LEDs than can be off, red or green. Four push buttons than can be labeled as desired, four toggle switches also labeled, four sliders labeled and with maximum values set. The text box accepts messages from the AtMega32U4. The virtual  I/O devices eliminate the need to connect physical pots and switches to the Mobillyo i/o pins freeing them up for other functions. See the serial protocol section for more information on the communication protocol.
  • The nrf52 can report the battery voltage and the solar panel power to the Mobillyo through the I2C interface.


The Mobillyo has a number of facilities for communicating with an iPhone, a computer, another Arduino, or other microcontrollers. The ATmega32U4 provides UART TTL (3.3V) serial communication, which is available on digital pins 0 (RX) and 1 (TX). The 32U4 also allows for serial (CDC) communication over USB and appears as a virtual com port to software on the computer. The chip also acts as a full speed USB 2.0 device, using standard USB COM drivers. On Windows, a .inf file is required. The Arduino software includes a serial monitor which allows simple textual data to be sent to and from the Arduino board. The RX and TX LEDs on the board are connected to the nrf52 and required sending messages over the I2C interface to turn these LEDs on or off. They will not flash when data is being transmitted via the USB connection to the computer. A SoftwareSerial library allows for serial communication on any of the Mobillyo’s digital pins. The ATmega32U4 also supports I2C (TWI) and SPI communication. The Arduino software includes a Wire library to simplify use of the I2C bus; see the documentation for details. For SPI communication, use the SPI library. The Mobillyo appears as a generic keyboard and mouse, and can be programmed to control these input devices using the Keyboard and Mouse classes. The AtMega32U4 communicates with the nrf52 and with the connected iPhone or Tablet using our proprietary protocol.


The Mobillyo can be programmed with the Arduino software (download). See the reference and tutorials. on how to incorporate the Mobillyo into the Arduino lDE.  The ATmega32U4 on the Mobillyo comes preburned with a bootloader that allows you to upload new code to it without the use of an external hardware programmer. It communicates using the AVR109 protocol. You can also bypass the bootloader and program the microcontroller through the ICSP (In-Circuit Serial Programming) header using Arduino ISP or similar; see these instructions for details. The nrf52 should not need programming, nevertheless a 10 pin 50mil 2×5 header footprint is available on the board. The Over the air firmware update feature will be implemented at a later date.

Automatic (Software) Reset and Bootloader Initiation

Rather than requiring a physical press of the reset button before an upload, the Mobillyo is designed in a way that allows it to be reset by software running on a connected computer. The reset is triggered when the Mobillyo’s virtual (CDC) serial / COM port is opened at 1200 baud and then closed. When this happens, the processor will reset, breaking the USB connection to the computer (meaning that the virtual serial / COM port will disappear). After the processor resets, the bootloader starts, remaining active for about 8 seconds. The bootloader can also be initiated by pressing the reset button on the Mobillyo. Note that when the board first powers up, it will jump straight to the user sketch, if present, rather than initiating the bootloader. A seperate reset switch is provided for the nrf52 BLE.
Because of the way the Mobillyo handles reset it’s best to let the Arduino software try to initiate the reset before uploading, especially if you are in the habit of pressing the reset button before uploading on other boards. If the software can’t reset the board you can always start the bootloader by pressing the reset button on the board.

USB Overcurrent Protection

The Mobillyo has a resettable polyfuse that protects your computer’s USB ports from shorts and overcurrent. Although most computers provide their own internal protection, the fuse provides an extra layer of protection. If more than 500 mA is applied to the USB port, the fuse will automatically break the connection until the short or overload is removed.

Physical Characteristics

The maximum length and width of the Mobillyo PCB are 2.7 and 2.1 inches respectively, with the USB connector and power jack extending beyond the former dimension. Four screw holes allow the board to be attached to a surface or case. Note that the distance between digital pins 7 and 8 is 160 mil (0.16″), not an even multiple of the 100 mil spacing of the other pins. The board is 20mm thick from the top of the headers to the bottom of the battery.

Let us know how you would use the Mobillyo and get a $5 discount coupon.

Installing the Mobillyo in the Arduino IDE Board Manager