This blog was originally published by Michael Stanley, manager of the systems/algorithms team within Freescale’s Sensors Solution Division, on the Embedded Beat.
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 Freescale’s new 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 Freescale’s 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. Budgetary pricing at Freescale.com (as of 5 Feb 2015) is $1.69 each in 1,000 unit quantities.
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 Freescale sensor fusion kit already supports the FXAS21002. Just change:
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.
Freescale is 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 osciloscope probes, through holes for DIP leads, and shorted resistors to enable easy current measurements.
BRKT-STBC-AGM01 Breakout Board
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. Freescale has 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 pace.