Eagle Tree Microsensor I2C Interface User Manual

Using eagle tree microsensor v3/v4, Sensors with your microcontroller project

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Copyright © 2009-2011 Eagle Tree Systems, LLC


Using Eagle Tree Microsensor V3/V4

Sensors with your

Microcontroller Project

Document Version 1.5

The Eagle Tree Systems G-Force, Airspeed, Altimeter V4, and Altimeter V3 sensors can be
incorporated in you microcontroller project. The sensors are accessed via the industry standard
I2C bus.

Data Format Returned

Altimeter V3 and Airspeed V3

When put in Third Party mode described below, the sensors return the actual speed or altitude, in
the units selected as described in the instruction manual that accompanies the sensors. Note that
the Altimeter V3 never reports below 0.

Altimeter V4

The Altimeter V4 reports altitude in decimeters (tenths of meters). The value returned is signed,
and is the actual barometric altitude, + 3000 decimeters. Subtract 3000 from the returned value
to determine the actual barometric altitude, or just use the initial returned value as the zero
reference point. The sensor will report negative altitude readings.


The G-Force Microsensors return signed centi-g (hundredths of g) readings for X, Y and Z (in
that order).

Configuring the Airspeed V3 and Altimeter V3 Sensors for “Third
Party” Mode

The Airspeed V3 and Altimeter V3 Microsensors need to be configured for “Third Party” mode
to use with your project. The Altimeter V4 and G-Force sensors do not have this requirement.

To configure the sensor to be accessible with your Microcontroller, you must first connect the
sensor to an eLogger V3/V4, and install Eagle Tree Data Recorder software version 9.57 or later.
Follow these steps to switch the sensor from “Eagle Tree” mode (raw data returned via I2C) to
“Third Party” mode (actual airspeed or altitude returned via I2C):


Install Data Recorder software version 9.57 or later.


Attach the MicroSensor to your eLogger V3 or V4, per the Microsensor instructions.


Connect the eLogger V3/V4 and Microsensor to USB.


In the Data Recorder software click "Advanced, Custom Hardware Options."


Click the appropriate checkbox (“Use my Airspeed V3 Microsensor with 3rd Party
hardware” or “Use my Altimeter V3 Microsensor with 3rd Party hardware “ to toggle the
sensor(s) between Eagle Tree and third party mode.