My friends, and probably most of you reading this, are well aware that I never
really grew up. In my heart, I’m still a boy who loves his toys. My
wife recently reconfirmed that by giving me a new microdrone quad-copter
(complete with camera!) for Christmas. The market for these has
exploded in the last couple of years, and I’ve been wanting to try one
out. Over my Christmas break, I learned that it’s easy to get one
in the air, but difficult keeping it there for more than a few seconds without
crashing or straying into the neighbors back yard (sorry about
that!). My little copter now has a healthy set of scars, and the
first set of spare parts to keep it air worthy are already in hand. But
the very fact that you CAN get these things to fly is absolutely
amazing. You’ve got four motors that must be independently
controlled to stay in the air. And if you cut power, they don’t
coast down, they drop. These devices really couldn’t be mass
produced until small, low power and inexpensive MEMS gyroscopes became widely
available. Which leads me to the FXAS210002 gyroscope,
which was released for mass production last month.
The block diagram for the 3-axis FXAS21002 (above) is pretty standard.
But this is our second generation gyro, and under the hood there are lots
of improvements. We’ve cut the power by 40% compared to our
biggest competitor, and now have an active supply current of
only 2.7mA. Standby current is less than 3
microamps. Dynamic range has been increased to +/- 2000 degrees/sec and
transition time from standby to active has been cut to 60ms + 1/ODR.
There’s an integrated 8-bit temperature sensor, 32-sample deep FIFO
and the part can automatically generate an interrupt output when measured
rates exceed a programmed value. Noise density has decreased to less
than 1/2 of the prior generation, and is now at 0.025 dps/root hertz.
The FXAS21002 is already supported by the
Intelligent Sensing Framework, which is now integrated into the
Processor Expert code generation tool (shown below). During the last couple weeks of
January, I traveled to Japan and Korea, teaching ISF 2.0 application
development to field application engineers in those locations. Using
ISF, I can generate a very nice embedded application for data logging in under
an hour. That includes sensor timing, communications, board feature
discovery, communications test, command protocol to/from a host PC and data
streaming.
The existing sensor fusion kit already supports the FXAS21002. Just change:
#define USE_FXAS2100
//#define USE_FXAS21002
to
//#define USE_FXAS21000
#define USE_FXAS21002
in build.h in the Sources directory. I will note that we’ve seen
improved startup and transient performance of our sensor fusion using the
21002 as compared with earlier 21000 gyro. I think you will be
impressed.
We are offering two development boards in support of the FXAS21002.
In addition to the gyro, they both also include a FXOS8700CQ combo sensor
(accelerometer plus magnetometer).
The BRKT-STBC-AGM01 breakout board ($11.95 USD) is shown
below. It has all the sensors you need to run 9-axis sensor fusion, as
well as points for attaching oscilloscope probes, through holes for DIP
leads and shorted resistors to enable easy current measurements.
The FRDM-STBC-AGM01 Freedom Shield board ($15.95 USD) is shown below.
You’ll note that it includes exactly the same layout as the breakout
board, and then wraps that with the standard Arduino pin connectors and a
couple of jumpers for I2C-bus selection.
Boards are being built now and distributors are stocking up on the gyro
piece parts. You should be able to order the FXAS21002 from your
favorite supplier this month.
And back to my lead-in, when coupled with our magnetic sensors, accelerometers
and free sensor fusion, this device becomes part of a compelling solution for
drone and navigation applications. We have been building a lot of
momentum in this area, and I’m really looking forward to putting that
first drone including the FXAS21002 through its paces.
