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Wiring of weather shield to DragonBoard 410c

Introduction

In this project, we will use a weather shield containing a HTU21D(F) humidity and temperature sensor and a MPL3115A2 pressure sensor connected to a I2C bus. We will use the SparkFun weather shield, which provides these two sensors and a light sensor. The GPIO of the DragonBoard includes the required I2C buses and 5V port to power the shield.

A push button will be connected to the GPIO. It will be used to activate voice recognition for operation without a keyboard and mouse.

Components

To connect the sensor to the DragonBoard, a level shifter will be necessary. The DragonBoard GPIO operates at 1.8V, while the weather shield outputs operate at 5V. A bidirectional level shifter is required due to the open drain nature of I2C, where both the master or the devices might pull the line low. A Adafruit 4-channel I2C-safe Bi-directional Logic Level Converter will be used.

Wiring

The Fritzing project with the connections can be downloaded here. Breadboard wiring

  • The GND signals of both boards are connected.
  • On the DragonBoard side, LV is connected to 1.8V, and A1 and A2 are connected to SCL and SDA, respectively.
  • On the weather shield side, HV is connected to 5V, and B1 and B2 are connected to SCL and SDA, respectively.
  • The DragonBoard's 5V output is connected to 5V and VIN of the weather shield.
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