The duties of a sensor hub are rather specific. They usually take the form of an additional micro-controller unit, a coprocessor or a DSP that integrates data from various sensors and processes them for the benefit of the main central processor. Not only does this technology off-load several jobs from the main central processing unit of a product, it saves battery consumption and provides an upward jump in its performance.
Most smartphone, tablet and wearable manufacturers including application developers are targeting mobile devices in the near future that will always be aware of their surroundings and activities. This will lead to providing meaningful results and content to the user. Inputs for the Always-on Context Awareness will be delivered by numerous sensors located within a mobile device, a separate micro-controller or a sensor hub fusing and computing their data.
PNI Sensor Corp. is making such a tiny 2×2 millimeter package as a sensor hub. It is by far the smallest, smartest and the lowest power-consuming implementation of a sensor hub. Consuming barely 200µA, this sensor hub implements the complete sensors function for the latest KitKat Version 4.4, as mandated by Google. Furthermore, PNI has incorporated all the KitKat functions without implementing an extra processor. This will greatly extend the battery lives of Android devices, even if they are using all their functions 24×7.
Android device manufacturers have two other choices. They could write their own fusion software and have them run on processors such as from Atmel or ARM. They could even license such software from others. On the other hand, OEMs could use smart sensors that have some functions implemented on-chip, while running the rest on the application processor. However, both the above methods are power-hungry and likely to consume up to ten times the power compared to the solution offered by PNI.
SENtral-K hub (the K standing for Google’s KitKat), from PNI can handle all the hardware connections from the MEMS sensors, while managing the virtual sensor functions in the software including the dedicated state-machine logic. The hub uses a tiny processor, the Synopsys ARC, along with specialized state-machines. Together, they achieve 140-thousand FLOPS or floating-point operations every second, while consuming less than 200µA at 1.8V. Being sensor agnostic, SENtral-K allows OEMs to select the lowest power consuming sensors from all different suppliers. This includes sensors such as for ambient light, pressure, proximity, magnetometer, gyroscope, accelerometers and many more.
SENtral-K combines all the outputs from the raw sensors and provides KitKat with the necessary functions it demands. These include functions such as step-detect, step-count, significant motion, linear acceleration including all the functions based on location and others that Google wants to incorporate at all times for their apps such as Google Now. The tiny chip comes fully pre-programmed to handle all functions demanded by Google’s KitKat 4.4.
For example, SENtral-K is capable of handling Android 4.4 KitKat functions such as those with nine degrees of freedom or DOF – 3-axis magnetometer, 3-axis gyro and 3-axis accelerometer. It can also handle six DOF – accelerometer and gyro or accelerometer and magnetometer. Other functions it can handle include Timestamp, Data Batching, Uncalibrated Sensor, Calibrated sensor, Significant Motion, Step Detect/Count, Linear Acceleration and Gravity.