What in the World is Contextual Sensing?

Contributed by Michael Stanley, Freescale Semiconductor

Originally posted on Freescale’s Smart Mobile Devices Embedded Beat blog

You can’t use your phone, drive your car or even nuke a sandwich without relying on one or more electronic sensors to help you complete the task.  Their use has become ubiquitous, and most people are blissfully unaware of just how much they depend on them in their daily lives.

Last year, Freescale announced it had shipped its one billionth sensor.  With that many units in the field, you would expect that they have evolved over time.  Yesterday, Freescale announced its new Xtrinsic Sensors brand.  With the new brand introduction, Freescale is stressing the concepts of Contextual Sensing andIntelligent Integration.

The basic idea is for the sensor to intelligently process sensed data, off-loading the master controller.  Accelerometers should not just provide numeric acceleration values, they should be able to count your footsteps when you walk from one local to another – at the same time that they are informing the applications processor in your phone that it’s time to switch the display from landscape to portrait mode.

When multiple types of sensors are packaged together, they should be able to infer information about their environment, and take advantage of that to perform tasks only when it makes sense to do so.  For instance, a 6DOF (degrees of freedom) system consisting of 3 axes of accelerometer data plus 3 axes of magnetic data may use the accelerometer to tell when the device is at rest, at which point, the magnetometer is automatically recalibrated.  In a 9DOF system, you could then use the magnetometer to keep gyro drift contained to a reasonable value.  A 10DOF system might add a sensor to measure air pressure, which can be used to imply altitude.  In that case, you might use your accelerometer data to differentiate between air pressure changes resulting from walking up a staircase from those resulting from the AC kicking on in your office.

Some of the features above are available today.  Some are still accomplished only with sensor fusion at the PCB level.  Over time, more of them will be available as integrated solutions.  I’m looking forward to being part of that evolution.

If you’re reading this blog, you probably share my interest in the sensors field.  Besides the usual technical rags like EDN or EE Times, you may also benefit by checking out the IEEE Sensors Journal and the Open Access Sensors journal.  Freescale also has an active channel on YouTube that includes a number of videos touching on sensor applications.

My next post will introduce the MMA9550L Motion Sensing Platform.  It’s a lot of fun in a very small package.  If you are designing power-sensitive portable systems that need to respond to user movements, this device is for you!

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