InvenSense MPU-6555 6-axis motion sensor for wrist-worn devices

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The MPU-6555 is InvenSense’s 6-axis (3-axis gyroscope + 3-axis accelerometer) activity detection device, working in conjunction with its Automatic Activity Recognition library (AAR) in a 3 x 3 x 0.9 mm (24-pin QFN) package. The product is suitable for Smart Watch, Smart Band and Fitness Tracker applications.

The unit uses data calculated on the on-chip DMP (digital motion processor) to recognise new activities typically within 10 s and with 95% accuracy for true positives. The AAR library offers a pedometer that benefits from the awareness of knowing which activities will require steps and which will not, as well as elevation tracking. The library is optimised to recognise the user’s ‘persistent’ activity, making it useful for cataloguing the user’s daily fitness level.

The product also features a 512 B FIFO that can lower the traffic on the serial bus interface and reduce power consumption. With its dedicated I²C sensor bus, the device directly accepts inputs from external I²C devices. It is also designed to interface with multiple non-inertial digital sensors, such as pressure sensors, on its auxiliary I²C port.

The gyroscope has a programmable full-scale range of ±250, ±500, ±1000 and ±2000 degrees/s and low rate noise at 0.01 dps/√Hz. The accelerometer has a user-programmable accelerometer full-scale range of ±2, ±4, ±8 and ±16 g. Factory-calibrated initial sensitivity of both sensors reduces production-line calibration requirements. Other features include on-chip 16-bit ADCs, programmable digital filters, a precision clock with 1% drift from -40 to 85°C, an embedded temperature sensor and programmable interrupts.