The Arduino Yún is a microcontroller board based on the ATmega32u4 and the Atheros AR9331. The Atheros processor supports a Linux distribution based on OpenWrt named OpenWrt-Yun. 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. Because the Yún has two processors, there is a separate table for the characteristics of each processor.
|Digital I/O Pins||20|
|Analog Input Channels||12|
|DC Current per I/O Pin||40 mA|
|DC Current for 3.3V Pin||50 mA|
|Flash Memory||32 KB (of which 4 KB used by bootloader)|
|Clock Speed||16 MHz|
|Ethernet||IEEE 802.3 10/100Mbit/s|
|USB Type-A||2.0 Host|
|Card Reader||Micro-SD only|
|RAM||64 MB DDR2|
|Flash Memory||16 MB|
For more details visit the Arduino website.