ARDUINO
YÚN
Code: A000008
Arduino YÚN is the perfect board to use when designing connected
devices and, more in general, Internet of Things projects. It
combines the power of Linux with the ease of use of Arduino
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 Linino OS. The board has built-in Ethernet and WiFi support, a
USB-A port, micro-SD card slot, 20 digital input/output pins (7 of them can be used
as PWM outputs and 12 as analog inputs), a 16 MHz crystal oscillator, a micro USB
connection, an ICSP header, and 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.
The Yún distinguishes itself from other Arduino boards by its ability to
communicate with the Linux distribution onboard, offering a powerful networked
computer with the ease of an Arduino. In addition to Linux commands like the
cURL, you can write your own shell and python scripts for robust interactions. The
Yún is similar to the Leonardo with the ATmega32u4, except that it has Linux on
board. (has built-in USB communication, eliminating the need for a secondary
processor).
NB: Yun Release 5 The new Arduino Yun R5 differs substantially from the previous
release in these features:
The power supply system provides 5V on AREF;
The layout has been modified, adding two holes for USB signals and two holes for GP6
and GPIO13(LED2).
Getting Started
In the Getting Started section, you can find
configure your board. Ready to get started?
Oct 2014, please check the Yún Open WRT
it after 2015 check Arduino Yún Linino OS
all the information you need to
If you bought your Arduino Yún before
OS Getting Started Page, if you bought
Getting Started page.
AVR Arduino microcontroller
Microcontroller
Operating Voltage
Input Voltage
Digital I/O Pins
PWM Output
Analog I/O Pins
DC Current per I/O Pin
Flash Memory
SRAM
EEPROM
Clock Speed
ATmega32U4
5V
5 V
20
7
12
40 mA on I/O Pins; 50 mA on 3,3 Pin
32 KB (of which 4 KB used by bootloader)
2.5 KB
1 KB
16 MHz
Arduino Microprocessor
Processor
Architecture
Operating Voltage
Ethernet
WiFi
USB Type
Card Reader
RAM
Flash Memory
SRAM
EEPROM
Clock Speed
Atheros AR9331
MIPS
3.3V
802.3 10/100Mbit/s
802.11b/g/n 2.4 GHz
2.0 Host
Micro‐SD
64 MB DDR2
16 MB
2.5 KB
1 KB
400 MHz
Power
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 support@arduino.cc
The power pins are as follows:
VIN. The input voltage to the Arduino board. Unlike other Arduino boards, if you are
going to provide power to the board through this pin, you must provide a regulated 5V.
5V. The power supply used to power the microcontrollers and other components on the
board. This can come either from VIN or be supplied by USB.
3V3. A 3.3 volt supply generated by the on‐board 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 5V on the Yún.
Memory
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).
The memory on the AR9331 is not embedded inside the processor. The RAM and
the storage memory are externally connected. The Yún has 64 MB of DDR2 RAM
and 16 MB of flash memory. The flash memory is preloaded in factory with a Linux
distribution based on OpenWrt called Linino OS. You can change the content of the
factory image, such as when you install a program or when you change a
configuration file. You can return to the factory configuration by pressing the
"WLAN RST" button for 30 seconds.
The Linino OS installation occupies around 9 MB of the 16 MB available of the
internal flash memory. You can use a micro SD card if you need more disk space
for installing applications.
Input and Output
It is not possible to access the I/O pins of the Atheros AR9331. All I/O lines are
tied to the 32U4.
Each of the 20 digital i/o pins on the Yún can be used as an input or output, using
pinMode(), digitalWrite(), and digitalRead() functions. They operate at 5 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 Yún, the Serial class refers to USB (CDC) communication; for TTL serial on
pins 0 and 1, use the Serial1 class.
The hardware serials of the ATmega32U4 and the AR9331 on the Yún are
connected together and are used to communicate between the two processors. As is
common in Linux systems, on the serial port of the AR9331 is exposed the console
for access to the system, this means that you can access to the programs and tools
offered by Linux from your sketch.
TWI: 2 (SDA) and 3 (SCL). Support TWI communication using the Wire library.
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. Is not
recommended to use pins 0 and 1 as interrupts because they are the also the hardware
serial port used to talk with the Linux processor. Pin 7 is connected to the AR9331
processor and it may be used as handshake signal in future. Is recommended to be
careful of possible conflicts if you intend to use it as interrupt.
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, but does NOT have a 6‐pin ICSP connector that connects to the Yún's 6‐pin ICSP
header, the shield will not work. The SPI pins are also connected to the AR9331 gpio pins,
where it has been implemented in software the SPI interface. This means that the
ATMega32u4 and the AR9331 can also communicate using the SPI protocol.
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. There are several other status LEDs on the
Yún, indicating power, WLAN connection, WAN connection and USB.
Analog Inputs: A0 ‐ A5, A6 ‐ A11 (on digital pins 4, 6, 8, 9, 10, and 12). The Yún 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 5 volts, though is
it possible to change the upper end of their range using the AREF pin and
the analogReference() function.
AREF. Reference voltage for the analog inputs. Used with analogReference().
There are 3 reset buttons with different functions on the board:
Yún RST. Bring this line LOW to reset the AR9331 microprocessor. Resetting the AR9331
will cause the reboot of the linux system. All the data stored in RAM will be lost and all
the programs that are running will be terminated.
32U4 RST. Bring this line LOW to reset the ATmega32U4 microcontroller. Typically used to
add a reset button to shields which block the one on the board.
WLAN RST. This button has a double feature. Primarly serves to restore the WiFi to the
factory configuration. The factory configuration consist to put the WiFi of the Yún in
access point mode (AP) and assign to it the default IP address that is 192.168.240.1, in
this condition you can connect with your computer to the a WiFi network that appear
with the SSID name "Arduino Yun‐XXXXXXXXXXXX", where the twelve 'X' are the MAC
address of your Yún. Once connected you can reach the web panel of the Yún with a
browser at the 192.168.240.1 or "http://arduino.local" address. Note that restoring the
WiFi configuration will cause the reboot of the linux environment. To restore your WiFi
configuration you have to press and hold the WLAN RST button for 5 seconds. When you
press the button the WLAN blue LED will start to blink and will keep still blinking when
you release the button after 5 seconds indicating that the WiFi restore procedure has
been recorded. The second function of the WLAN RST button is to restore the linux image
to the default factory image. To restore the linux environment you must press the button
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