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Adding Internet connectivity to Arduino boards and apps with the YUN Shield

Adding Internet connectivity to Arduino boards and apps with the YUN Shield
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On the shield, there are four LEDs with the following functions:

  • PWR: Power LED. It lights up when the shield is on;
  • LAN: is on or flashing to indicate the presence of a network connection;
  • WLAN: Indicates a working WiFi connection;
  • SYS: Indicates the presence of an USB memory. When lit, it indicates that the folders on the USB mass storage device are mounted on / mnt, /mnt/sd and /www/sd respectively.



Multifunction button

On Yun shield there is only one button, labeled “Failsafe”, to manage the reset and restore operations, which may be necessary sometimes. When the shield is on, after the boot process is over, holding pressed the failsafe button for 5 seconds resets to factory settings the WiFi chip configuration. 


Holding it for 30 seconds sets the whole shield to factory setting. The third use of the failsafe button is to initiate the board recovery function in case of wrong firmware upgrade. This process is very complex and too long to describe it in this article. The recommendation that we can give is to upgrade the firmware carefully to avoid being with the shield unusable. In any case the “rescue” instructions can be found at


Power modes

A major issue when using Yun shield is how the power it. The shield is powered through GND and VIN pins. The recommended way is to use these pins. The Dragino HE module, which is the heart of this shield, requires a 200 mA current at full load, so it is a best practice to connect it to the pins said before rather than overheating the 5V LDO (low drop out) power supply module. In this configuration, it is better to power Arduino through its DC connector and not by the USB port. Be careful to use an external power supply providing more than 7V input voltage.




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