Gestures, Gaming, Gyroscopes
The integration of gyroscopes and of other inertial sensors has reached a degree of technical maturity which provides a simple and cost-efficient means to recognize and process motion in consumer devices.
Looking for promising product advantages, manufacturers have begun to implement such sensors into mobile phones, security cameras or TV remote controls which recognize gestures, to optimize images or for motion-driven menu navigation.
However, the key to success in this market segment is the know-how permitting cost-effective manufacturing and the broadest possible software support for customer applications. InvenSense, leading manufacturer of MEMS gyroscopes thanks to its Nasiri platform, has recently set new standards with regard to costs and integration with its MPU-6000.
Sensors and metrology on one chip
With its integrated 3-axis gyroscope and 3-axis accelerometer chip in addition to the Digital Motion Processor™(DMP), which is able to carry out complex 9-axis sensor fusion calculations, the MPU-6000 represents a breakthrough in MEMS sensor technology, primarily because this chip eliminates the challenges linked to selecting and implementing different motion sensors, i.e. signal conditioning, sensor fusion and calibration during production. The MPU-6000 provides integrated 9-axis sensor fusion algorithms and uses an external compass sensor via I2C bus in order to provide additional support for 9-axis applications such as deadlock reckoning.
MPU-6000 ICs are available mounted inside the same 4x4x0.9 mm QFN package and with the same pinning as the current chips of the MPU-3000 family (3-axis gyroscopes), simplifying their deployment on existing boards. The I2C bus or SPI bus, the Standard MotionProcessing-Library™ (MPL) as well as the corresponding API simplify integration and connection to a wide range of application processor
The MPU-6000 provides programmable resolutions of ±250dps, ±500dps, ±1000dps up to ±2.000dps (= degrees per second) for angular rate measurements and ±2g, ±4g, ±8g or ±16g for linear acceleration measurements.
This enables the deployment of a single MotionProcessing solution for each conceivable motion application, from a rather comfortable menu navigation with remote controls to the recognition of unwanted camera shake - all of which is digitized at 16 bit and with a few hundred samples per second. With its noise ratio of 0.005 degrees/sec/vHz, the module sets new industry standards and thus provides the highest quality and user-friendliness for image stabilizers or for pointing & gaming applications. Precise calibration with a tolerance of ±1% for the initial sensitivity reduces the requirement for fine adjustments by the user.
The gyroscope works with a resonance frequency in excess of 27 kHz and is thus largely immune against interferences of audible frequencies (20 ... 20,000 Hz) such as music or ringing phones, which is very important for noise-sensitive applications such as image stabilizers.
Further industry-leading characteristics are a 4x4x0.9mm, 24-pin QFN plastic package, on-chip 16-bit ADCs, programmable digital filters, precision clocks with a tolerance of 2% between -40°C and 85°C, embedded temperature sensor, programmable interrupts and a low power consumption of only 5.5 mA. These chips are available with I2C or SPI interfaces, an operating voltage of between - 2.5 and 3.6 V and a VLOGIC-interface voltage from 1.71 to 3.6 V.
One decisive advantage of an integrated 6-axis on-chip solution is the perfect alignment of all axes of the gyroscope and the accelerometer, eliminating the requirement for expensive calibrations which are necessary for separate solutions.
Furthermore, a complete 9-axis sensor fusion system can be realized with the master I2C bus which takes over 3-axis compass measurements, using IvenSense's proprietary and patented DMP & MPL functions. IvenSense's MPL is a software layer which facilitates the integration and connection of application processors.
InvenSense's most recent version of the motion processing library software, V3.2, now also supports the Android 2.3 "Gingerbread" operating system, amongst many others. Together with the linked MotionProcessor product range, this software provides a comprehensive solution for 9-axis sensor fusion with individual 3-axis turn rates (gyroscope), acceleration (accelerometer) and heading (compass sensor) for the structures of the Android-Gingerbread programming interface (API).
The new APIs (Quaternion, rotation matrix, linear acceleration and gravity) enable application developers to benefit from the advantages of combined sensors for gyroscopes, acceleration and compasses. The MPL 3.2 software solves the problems related to the integration of numerous sensors into the Android operating system by connecting directly to the Gingerbread hardware abstraction level (HAL) and by delivering 9-axis sensor fusion data to the new APIs without the requirement for complex, processor-hungry calculations of motion algorithms by the application processor. This is achieved by coordinating the MPL with a Compagnion MotionProcessor featuring embedded DMP and integrated motion algorithms, in order to relieve the application processor from 9-axis sensor fusion calculations.