The Arduino Yun is a microcontroller board based on the ATmega32u4 (datasheet) and the Atheros AR9331. The Atheros processor supports a Linux distribution based on OpenWRT named Linino. The board has built-in Ethernet and WiFi support, a USB-A port, micro-SD card slot, 20 digital input/output pins (of which 7 can be used as PWM outputs and 12 as analog inputs), a 16 MHz crystal oscillator, a micro USB connection, an ICSP header, and a 3 reset buttons.
NB : In some countries, it is prohibited to sell WiFi enabled devices without government approval. While waiting for proper certification, some local distributors are disabling WiFi functionality. Check with your dealer before purchasing a Yún if you believe you may live in such a country. If you wish to disable WiFi, run this sketch. For more information, refer to this forum post.
The Yún distinguishes itself from other Arduino boards in that it can communicate with the Linux distribution onboard, offering a powerful networked computer with the ease of Arduino. In addition to Linux commands like cURL, you can write your own shell and python scripts for robust interactions.
The Yún is similar to the Leonardo in that the ATmega32u4 has built-in USB communication, eliminating the need for a secondary processor. This allows the Yún to appear to a connected computer as a mouse and keyboard, in addition to a virtual (CDC) serial / COM port.
The Bridge library facilitates communication between the two processors, giving Arduino sketches the ability to run shell scripts, communicate with network interfaces, and receive information from the AR9331 processor. The USB host, network interfaces and SD card are not connected to the 32U4, but the AR9331, and the Bridge library also enables the Arduino to interface with those peripherals
The Yún has two processors, the specifications section shows the characteristics of each one in two separate tables. AVR Arduino Microcontroller
Digital I/O Pins
Analog Input Channels
DC Current per I/O Pin
DC Current for 3.3V Pin
32 KB (of which 4 KB used by bootloader)
IEEE 802.3 10/100Mbit/s
64 MB DDR2
PoE compatible 802.3af card support
X000002 PoE module is not compatible. Requires 5V module
It is recommended to power the board via the micro-USB connection with 5VDC.
If you are powering the board though the Vin pin, you must supply a regulated 5VDC. There is no on-board voltage regulator for higher voltages, which will damage the board.
The Yún is also compatible with PoE power supply but in order to use this feature you need to mount a PoE module on the board or buy a preassembled board.
Note : early models of the Yún with a PoE adapter were incorrectly providing the board with 12V. An updated version will soon be provided to distributors that provide the expected 5V. If you believe you have the wrong PoE adapter on your board, please contact firstname.lastname@example.org