POWER:
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.
Start the Arduino IDE and find ArduBlock under the Tool menu. I'm trying to use variables, but Ardublock does not appear to declare the variable type? I am attempting to use the Arduino IDE with Mint 19 Tara. In the IDE menu I was able to select the board that I have but cannot select the serial port. The port menu item is greyed. If not, how can I replace with the new 2.2pre2+dfsg1-2?
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.
INTERFACE:
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.