Electronic products ranging from mobile phones to fitness
monitors may soon be smarter than ever. Thanks to sensors with onboard
intelligence, those products will be able to "think" as never before, gathering
data and then using it to reach conclusions - not just about the information
gleaned from a single sensor - but about the world around them.
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electronics industry, the new breed of sensors represents a small revolution of
sorts. Freescale Semiconductor
, a component
supplier that's just now bringing the technology to market, says that the micro-machined
smart sensors could enable everyday products - such as automotive airbags or iPhones
- to put their knowledge into context.
more, it's not just about taking in the data from a single element, but about
understanding everything around you," says Wayne Chavez, operations manager for
consumer and industrial sensors at Freescale. "Whether it's altimetry,
directional heading, or just the pace that you're walking, all these things are
measurable. And all of them can be put into the context of your surroundings."
"contextual" sensing represents a stark departure from the embedded computing
that's gone on up to now. The reason: Most of today's sensors are dumb; they
take an analog pressure or temperature reading and send it off to a
microcontroller, which does the thinking.
believes there are profound advantages to be realized by changing that
scenario. That's why the company has invested in the development of a two-level
sensor - a MEMS sensor chip, such as an accelerometer, stacked atop an ASIC
(application specific integrated circuit) incorporating a microcontroller. In
this embodiment, the CMOS-based ASIC chip houses the brains, as well as an
interface to an I2
C communications databus. During operation, it
takes the analog signal from the sensor chip above it, then using information
that's available from the databus, begins to put the information into a larger
advantages are not only that the "thinking" takes place on board the sensor,
but that the sensor offloads computing chores from the main CPU and saves power
in the bargain. The configuration is especially enticing to designers of smart
phones, who now must integrate readings from GPS systems, pressure sensors,
accelerometers and a half-dozen other sources.
of this data comes into the phone and the question becomes, how do you manage it
all?" Chavez asks. "You could manage it with your applications processor and be
interrupted every time you receive a pressure sensor reading, magnetometer
reading or gyroscope reading. Or you could put the intelligence on the sensor."New Frontier of
Freescale engineers cite the automotive airbag as a product that
could benefit from contextual intelligence. Airbags, which do an exceptional
job of being available when called upon, are nevertheless known to have rare
inadvertent deployments - or worse, no deployment when needed. Most such
situations occur when the integrity of a sensor signal is breeched, causing the
controller to inappropriately disable or enable a bag.
Freescale believes it can reduce or eliminate those situations by building
self-diagnostics into the sensor. "We're reaching the point where we can check
ourselves, more often and in real time, to better understand the integrity of a
measurement," says Jim Grothe, marketing manager for Freescale's MEMS
Automotive Business. With smart sensors, Grothe says, airbag modules would be
unlikely to make wrong decisions based on a single-point, faulty sensor
smart sensors could enable airbag systems to be more selective. By
communicating with one another and understanding the nature of a particular
crash, the airbag system might be more able to turn on and off the appropriate
bags, thereby saving on replacement costs. "If you have a front-end crash, you
might only want the front airbag to deploy," Grothe says. "If you have a
rollover and there's no frontal impact, maybe you don't want that front bag to
Nowhere, however, are the
advantages of smart sensors more evident than in the new breed of mobile
phones. There, the proliferation of applications is growing so fast that many
engineers are hard-pressed to keep up with them. Many phones now incorporate
accelerometers for gesture recognition, magnetometers for heading information, GPS
for location, gyroscopes for game play and even pressure sensors that serve as barometers,
helping users transform their phones into mini-weather stations.
Smart sensors become especially
important in such products because the applications are often interdependent.
To accurately measure a magnetic field vector, for example, the phone must know
its own orientation - that is, if the user is tilting it up or down, or holding
"The three-axis accelerometer
becomes critical for making other measurements," Chavez says. "No matter how
you hold your handheld device, you have an orientation based on gravity, and
that has to be used to auto-correct the measurement that describes your
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Freescale says it's ready for such
complex applications. In June, the company rolled out a MEMS-based
accelerometer called the MMA9550L
which incorporates a ColdFire 32-bit processor, along with databus connectivity
and power management in a 3 x 3 x 1 mm package. More recently, it has
introduced a magnetometer-based sensor, along with software solutions for
gesture recognition systems and pedometers, to its Xtrinsic
line of sensors. Ultimately, the company's engineers say they will pack a
gyroscope, pressure sensor, touch sensor and magnetic sensor in a 5 x 5 x 1 mm
package, along with the accelerometer and processor.
The company's engineers believe the
idea of a sensor with onboard intelligence will grow and creep into new
applications, including monitors for fitness, home heath and onboard tire
pressure, as well as e-book readers and tablet computers.
"There are still going to be some
applications that will still use traditional sensors," Chavez says. "But for
these sensors, the frontier is wide open to discovery." †