Arduino Yun Mini Development Board

The Arduino Yun Mini is a new and highly compact mini wireless development board that offers an affordable, small and lightweight Linux-based WiFi prototyping solution. Designed for use by embedded engineers, hackers and students, the Arduino Yun Mini is a redesign of the Arduino Yun WiFi microcontroller board and has been re-engineered to be used with a breadboard to make prototyping easier.

 

 

Highly Compact Design

Providing its functionality in a light and highly compact package, the Arduino Yun Mini has approximate board dimensions of 71.1mm x 22.9mm, which is less than half the area of the Arduino Yun PCB, which has dimensions of approximately 68.6mm x 53.3mm with its USB connector extending the length to approximately 73mm. In addition, the weight of the Yun Mini 16g is half that of the Yun. The board’s small size makes it ideal for use in small spaces and especially projects for home automation.

 

 

Microcontroller and Processor

The Arduino Yun Mini offers an affordable breadboard PCB with an ATmega32u4 microcontroller and the Qualcomm Atheros AR9331 system-on-chip IC with a MIPS 24K CPU, which operates at up to 400MHz and supports a Linux distribution based on OpenWRT called Linino. A bridge library enables communication between the two processors, providing Arduino programs the ability to run shell scripts, communicate with network interfaces and receive information from the AR9331 processor.

The Arduino Yun Mini is similar to the Arduino Leonardo in that the ATmega32u4 has built-in USB communication, eliminating the need for a secondary processor, which allows the Yun Mini to appear to a connected computer as a mouse and keyboard, as well as a virtual (CDC) serial/COM port.

 

Features and Accessories

The board has built-in WiFi connectivity (IEEE 802.11b/g/n operation up to 150Mbps) and supports 20 digital input/output pins, seven of which can be used as PWM outputs and 12 as analogue inputs. Other specifications include 16MHz crystal oscillator, micro-USB connector, an ICSP header, two reset buttons and one user button. The board can be powered via the micro-USB connection with 5V DC, which is the recommended option. However, a regulated 5V DC can also be used to power the board via the Vin pin.

The Arduino Yun Mini can be customised from a choice of up to two out of three available accessories, which are the dogRJ45, the dogUSB and the dog eMMC. The dogRJ45 is a 10/100-Mbps Ethernet port; the dogUSB is a USB A type connector with USB 2.0 hub that features a slot for a mini SD to extend the memory of the board; and the dogUSB eMMC is a USB port type A with an integrated 4GB of Flash.

 

Memory

The Arduino Yun Mini board also comes with 64MB of DDR2 RAM and 16MB of Flash memory, which is factory preloaded with the Linino OS occupying approximately 6MB of the 16MB available. The dogUSB and micro-SD card or dog eMMC and a 4GB Flash drive can be used to deliver more space for installing applications. The content of the factory image can be changed with the installation of a program or the modification of a configuration file, but the factory configuration can be restored by pressing the ‘WLAN RST’ button for 30s.

The ATmega32u4 MCU comes with 32KB of internal memory with 4KB used for the boot loader. It also has 2.5KB of SRAM and 1KB of EEPROM, which can be read and written with the EEPROM library. The AR9331 RAM and storage memory are not embedded, but are externally connected.

 

Communication

The board has a number of facilities for communicating with a computer, another Arduino or other microcontrollers. The ATmega32U4 MCU provides a dedicated UART TTL (5V) serial communication and also allows serial (CDC) communication over USB, appearing to computer software as a virtual com port. The chip also acts as a full-speed USB 2.0 device using standard USB COM drivers. The Arduino software also includes a serial monitor, which allows simple textual data to be sent to and from the Arduino board.

 

Programming

The Arduino Yun Mini can be programmed with Arduino software downloaded from arduino.org/downloads or the Linino IO from www.linino.org. The ATmega32U4 MCU comes pre-burned with a bootloader that allows the upload of new code without the use of an external hardware programmer, communicating via the STK500 protocol. The bootloader can also be bypassed and the MCU programmed via the SPI signals available on the pin headers.