Arduino yun is a microcontroller based on Atmega32u4 and Ar9331. Ar9331 running a named Linino OpenWrt Linux system. This controller with network communication and support Wifi, USB - A port, Micro - SD slot, 20 input/output pins (including 7 can be used for PWM output, 12 can be used for analog input), 16 MHz crystal vibration, Micro USB interface, ICSP interface, and A reset button.
YUN has two processors:
1.AVR Arduino controller
- Working voltage：5V
- Digital I/O interface：20
- PWM channel:7
- analog input channel：12
- Each I/O pins dc output current is 40 mA, 3.3 V dc output current 50 mA pin
- Flash：32 KB (including 4 KB for bootloader)
- SRAM：2.5 KB
- EEPROM：1 KB
- clock rate：16 MHz
- processor：Atheros AR9331
- architecture：MIPS @400MHz
- Working voltage：3.3V
- network：IEEE 802.3 10/100Mbit/s
- WiFi：IEEE 802.11b/g/n
- USB type-A：2.0 Host/Device
- Card reader：Micro-SD only
- RAM：64 MB DDR2
- Flash：16 MB
- PoE Compatible with 802.3af
- Overall dimensions：68.6*53.4 mm
Function is introduced
Main components of
In Yun small boards used to two processors. Is an ATmega32u4 label (6), it is the Arduino end controller, and the connection is MicorUSB (grade 8) and two rows of data and ICSP socket head (grade 4). Another processor in grade three parts, and it is connected to the network interface (grade 1), USB host (grade 7) and WIFI (grade 2). The role under review in various parts of the label:
- Network interface (grade 1) : RJ45 interface, that is our common cable network interface, it is used to connect cable network.
- WIFI module (grade 2) : WIFI module, used to connect to a wireless network;
- AR9331 processor (grade 3) : Linux end processor, it was running OpenWrt - Yun based on Linux system, its purpose is to perform some of the commands of Linux end;
- ICSP head (grade 4) : it is usually used to debug the ATmega32u4. Usually to ATmega32u4 upload program is through the MicroUSB, after the guide part damage, will need to use the ICSP to rebuild the boot. Of course some shield plate also use it to transmit data;
- Instructions chy-tech (grade 5) : the corresponding indicator light have different functions, this in 1.4.2 is introduced;
- ATmega43u4 label (6) : the Arduino end processor, it mainly control the two rows of socket on the Yun, after the main part of the programming is against it;
- USB Host (grade 7) : can connect all kinds of using this interface standard equipment, such as the camera;
- MicroUSB (8) label: function including supplies power for the whole board and ATmega32u4 programming.
- VIN: external power supply interface, can only meet stable 5 VDC
- 5V： Short answer the VIN, ditto
- 3V3: By the board of stabilivolt step-down and the output voltage of 3.3 V
- IOREF: I/O pin output reference voltage, YUN defaults to 5 v
YUN has 32 k ATmega32U4 chip space (4 k for BOOTLOADER), 2.5 KB SRAM, and 1 KB block of the EEPROM.
AR9331 using external storage devices. He contains 64 MB of DDR2 RAM and 16 MB of FLASH. Has the factory installed FLASH LININO version of OPENWRT. You can according to your need to change the configuration file. Long press WLAN RST 30 seconds can restore to factory Settings。
Input and output
- AR9331 pin can not be used. YUN all IO mouth from the AVR.
- All of the 20 digital I/o can be used as input or output. Method of use for invoking pinMode (), digitalWrite (), digitalRead (), three functions. Their working voltage of 5 v. Each IO can maximum pumping 40 ma current, pull up resistors and built-in 20-50000. Part of the IO and other functions.
- Serial port: 0 RX, 1 TX. The AVR hardware serial port. On the YUN, the call to the IDE SERIAL function is no longer access ATmega32U4, but access to the USB. ATmega32U4 hardware SERIAL port is connected with AR9331. If you want to use a serial port to access ATmega32U4, requires the operating AR9331 LINUX system to complete, you can directly use LINUX struggles serial command or use the relevant software.
- TWI/IIC ： 2 SDA, 3 SCL。
- Interruption of external interrupt: 3 interrupt 0, 2 1, 2 0 interrupt, 1 interrupt 3, 4 7 interrupt. These external interrupt can be set by the interrupt trigger conditions, such as low level trigger, falling edge trigger, rising along the trigger. Do not recommend using 0 and 1 foot, because they are connected with AR9331 do serial communication. The same 7 feet is not recommended, because he will be used in a later version and AR9331 handshake signals. Use of 0 1 7 feet will bring inconvenience to your design.
- PWM: 3 5 6 9 10 11 13, these pins can provide 8-bit PWM output.
- SPI/ICSP: These support pin SPI communication interface,
- It's important to note that YUN, unlike UNO, YUN SPI is not connected with any digital IO port, and connect with ICSP port. If you want to use any shield plate, using a digital IO SPI shield plate will not work.
- SPI interface at the same time also received a general IO AR9331, users can use SPI as second ATmega32U4 and AR9331 communication interface.
- LED: PIN 13 LED as well as other ARDUINO, output high light, low output.
- Analog Input: A0- A5, A6-A11(corresponding to the digital port 4,6,8,9,10,12). YUN has 12 analog input, from A0 - A11. All analog input interface can be used as digital I/o. A0 - the A5 on a plate and UNO. A6 - A11 on number 4,6,8,9,10,12 mouth. All analog input for 10 precision. In the default reference voltage is 5 v, under the regulation of 0 ~ 1024 corresponding to 0 ~ 5 v. Such as the user needs to adjust the reference voltage.
- AREF analog input port of the reference voltage input port.
- ARDUINO YUN, a total of three reset button. As shown in figure:
- YUN RST: after pressing the reset AR9331, AR9331 will restart, all the data in RAM disappears, the running program will be forced to shut down, LINUX will restart.
- 32U4 RST : After pressing the reset ATmega32U4.
- WLAN RST: The key has two functions：
Hold for 5 seconds after the release for the reduction of WIFI factory Settings。
Hold for 30 seconds after release to restore factory Settings of LINUX.
- Communication: the ARDUINO yun can have very many communication equipment and computer, other ARDUINO, or other single-chip microcomputer communication. ATmega32U4 built-in UART TTL port, virtual COM port, and the standard usb port. By using ARDUINO IDE serial port monitor can simply send the data to the ARDUINO YUN. When there are data transmission, RX and TX two leds will glow.
- serial port
- Digital port 0, 1 is used for ATmega32U4 and AR9331 communication interface.
- Software serial port: if the user needs to use a serial port connection ATmega32U4, using software to simulate a serial port.
- IIC interface
- SPI interface
- Analog keyboard and mouse input
- Internet and WIFI
- USB: AR9331 with LINUX system manages a USB port, you can use an external USB flash memory, keyboard, mouse, etc. Some devices may require the other driver.
- ARDUINO YUN use ARDUINO IDE 1.5 to programming, upload programs to YUN in TOOL -- > need before hanging BOARD menu ARDUINO YUN.
- ATmega32U4 presintering a BOOTLOADER that let users do not need to purchase additional burning device can add modification ATmega32U4 within the program.
- Users can bypass the BOOTLOADER that use ICSP to download the program.
Software restart and BOOTLOAD initialization
In Leonardo was set for the upload, the software to establish a connection to the controller reset, thereby removing our operation manual reset button. When Leonardo as virtual serial/COM port (CDC) at 1200 baud rate is running, will be contributed to reset function, a serial port will be closed. At this point, the processor will reset, USB connection is disconnected (that is, the virtual (CDC) serial/COM ports will disconnect). Processor reset bootloader then after the launch, probably waiting for 8 seconds to complete the process. Bootloader can also panel by pressing the reset button to start. Pay attention to when the board electricity for the first time, if there is a user program, he will jump straight to the user program, and not to start the bootloader. Leonardo is the best way to reset handle before upload programs to the arduino software end trying to start the reset function, but not you manually clicking the reset button. If the software does not make panel reset automatically, you can also manually by pressing the reset button to make the board reset operation boot.
USB overload protection
ARDUINO YUN, bringing a recoverable insurance to protect its USB port, when the USB port of the current more than 500 ma, the fuse will automatically shut off the USB interface until the current back to within 500 ma.
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