Yun Shield is an Arduino Shield which will simply "turn" Arduino (Leonardo, UNO, MEGA2560 etc) alike a "Arduino Yun" . It provides a Linux system, WiFi, Ethernet to the Arduino board for connectivity. It also has a USB host port which connect to the Linux system, this port can be used for storage, 3G, Video purpose.
Yun Shield runs Open Source OpenWrt system (Same system as runs in Arduino Yun) and it is fully compatible with Arduino IDE v1.5.4 or later. Yun Shield is the ideally choice for Arduino Projects which require various internet connections and more storage.
Basically, Yun Shield + Leonardo equally to the official Arduino Yun, but Yun Shield is more flexible because it can work with other Arduino board such as Uno, Duemilanove, Mega etc. And Yun Shield uses external wifi antenna which provides stability and possibility for various environments.
Step 1: Understand the structure of Yun Shield
The Dragino HE is the core module of Yun Shield. The HE module requires around 200ma current when in full load, so it is powered by the Arduino VIN pins to avoid overheated in the Arduino onboard 5v LDO. So when Yun shield is in used, the Arduino board should be powered by DC port instead of USB port. The DC input can be 7v ~ 15v.
The USB Host of Yun Shield gets power from the Arduino +5v pin, since the +5v from Arduino comes from the +5V LDO, to avoid overheated on the Arduino Board, when the USB host is in used, it is recommended to use +7v DC.
The RJ45, WiFi, USB Host and Failsafe are connected to the Dragino HE module directly. And the
Dragino HE module use SPI and UART to communicate with Arduino Board. Yun Shield is compatible with 3.3v and 5v Arduino board. The on board jumper SV1 is used to set the SPI and UART to 3.3v or 5v level.
The SPI interface is used to upload the sketches comes from the Arduino IDE. SPI interface only connects to Dragino HE during uploading so the Arduino SPI can still be used to connect to other SPI slave devices.
The UART interface is used for the Bridge class in Arduino, there are lots of examples explain how to use the bridge class in the Arduino IDE. It is the core of Yun solution. We must make sure the serial Interface of Arduino is not used by other hardware.
Step 2: Connect it to Arduino Leonardo and Power it via DC jack
Put the Yun Shield on top the Arduino and power it via DC jack
Step 3: Use computer to connect to Yun Shield
At the first boot of Yun Shield, it will auto generate an unsecure WiFi network call Dragino2-xxxxxx
Use a laptop to connect to this WiFi network. The laptop will get an IP 192.168.240.xxx and the Yun Shield has the default IP 192.168.240.1
Once the computer joins the network, open web browser (recommend Firefox and Chrome) and enter 192.168.240.1 to enter the Yun Shield setting page.
Default Password for Yun Shield is Arduino.
Step 4: Set up for Internet access and detect Yun shield on Arduino IDE
After log in, the GUI will show the WIFI / ETH interface status. Click the Configure button and now user can configure Yun Shield to access internet via your WiFi router.
Assume your laptop and Yun Shield are in the same network. The Yun Shield will broadcast data in this network and Arduino IDE will receive this data and show the Yun Shield in Tools -->Port.
Step 5: Upload Sketch
Step 6: Understand Bridge Library
The Bridge Library simplifies the communication between the Arduino Board and Yun Shield.
Bridge commands from the AVR (Arduino Board) are interpreted by Python on the Yun Shield. Its role is to execute programs on the GNU/Linux side when asked by Arduino, provide a shared storage space for sharing data like sensor readings between the Arduino and the Internet, and receiving commands from the Internet and passing them directly to the Arduino.
There are detail explain and lots of example to show how to use Bridge in the Arduino Official Website. Reference link Yun Bridge Library
Step 7: Example: log sensor data to Xively
This example shows how to log data to the public IoT server "Xively". The example can be found from Arduino IDE--> File --> Examples --> Bridge --> XivelyClient. Tutorial of this example can refer http://arduino.cc/en/Tutorial/YunXivelyClient.
Before upload the sketch, make sure:
Step 8: Some advantages for Yun Shield over Arduino Yun
The Yun shield can be used with different Arduino Boards and different type of avr.
Stable WiFi performance:
Yun Shield use external Antenna to ensure for the better wifi performance, the Arduino Yun use on board antenna, while place an Arduino Shield on top of Arduino Yun, the wifi performance will be strongly decreased because the antenna is under a PCB.
Flexible WiFi design: external antenna provides the feasibility to put the device into a metal enclosure. User can also change the antenna to different antenna type for their project wise. For example, the can set up several kilometers wifi connection with an outdoor directional antenna.
Duplicable and producible:
The design of Yun Shield is open and the most complicate and difficult parts are done in the Dragino HE module. User can use the Dragino HE module to make a customized Yun style product for their products in an easy/rapid/inexpensive way.