Gyros and accelerometers get their own smarts and APIs
MEMs-based motion sensors like 3-axis accelerometers and gyroscopes are moving from the realm of
“nice to have” to “must have” in handheld consumer devices. Gesture-based controls as well as inputs for navigation devices and gaming controls all rely on motion sensors. These MEMs devices are jostling with each other as well as other smart phone components for processor and I2C bus bandwidth – one number I heard put motion-related algorithmic number crunching at 10% of a smart phone’s total processing chores.
It seems like integrating a hardware accelerator with the accelerometer or gyro would be an excellent way to offload the application processor and bus, but there are problems with that. Despite the fact that MEMs sensors are built upon silicon, it’s a different process than integrated circuits: MEMs are big geometries, ICs are small, and never the twain shall meet.
Except that InvenSense has been able to surmount these problems and combine sensor technology with IC technology right on the same wafer, resulting in what it calls a MotionProcessor. The MPU-6000 combines a 3-axis gyro, a 3-axis accelerometer, and sufficient on-board intelligence to perform 9-axis sensor algorithms. (The other 3-axis comes would come from an external 3-axis compass.)
What about the problem of developers not wanting to get locked in one particular chip’s hardware instruction set? The clever folks at Apple with their iPhone and the equally clever folks behind the Android have allowed for a sensors API within the operating system which the MPU-6000 can support. (Here’s a link to the SensorManager on the AndroidDeveloper site.)
Next question: what about cost? Steve Nasiri, InvenSense’s CEO, estimated that the price Apple is currently paying for the iPhone’s 3-axis gyro is $2.50. It’s paying probably about 40 cents for its current 6-bit accelerometer, but to step it up to the next generation of apps and games will require a 10-bit low-noise accelerometer costing about 70-80 cents. On the other hand, the gyro price will probably drop to about $2, he estimates, by the end of next year. All in all, it sound like the MPU-6000 will sell at a production price next year of under $3.00.
InvenSense is a fables company. Impressive that they’ve been able to use foundries to integrate complex processing functions in MEMs when companies with their own foundries have been less successful. Below is a diagram of their MEMs platform and a link to an explanation of their technology.