New-Tech Europe Digital Magazine | Feb 2016

processor. Such drivers are specific for the module and include the communication protocol as well. Choices need to be made for the hardware layer (e.g. I2C, SPI, UART) and the communication protocol. The communication protocols used by some modules are flexible in terms of output configuration and/ or integration level. For example, the communication protocol of Fairchild’s FMT1000 series is implemented for low-level binary communication, for C/C++ interfaces and as DLL/.so for Windows/Linux. Ready-to-run sample code is available for ARM ® mbed™. Test and Calibration System integrators face several challenges when mounting MEMS on a board. For instance, the soldering process may influence the factory (statistical) calibration. A module, in which the inertial sensors are mounted, doesn’t have these detrimental effects. The calibration parameters in discrete inertial sensors are statistical values. This means that the variability is significant. Accelerometer biases of

specifications is often required. Next is the need for knowledge of MEMS, sensors and sensor fusion, which is also time-consuming. Another challenge in the quickly changing landscape of MEMS sensors is that keeping track of changes and EOL/PCN-notices by vendors also consumes valuable time. Dedicated MCU Retrieving data from the MEMS sensors is the first step. The next step is to find an MCU to process this data. This requires making estimations to determine the required RAM and program memory, necessitating advanced knowledge of the sensor fusion algorithm, OS, drivers and signal processing. The type of processor selected has a significant impact on system architecture, and without experience in designing an IMU and associated signal processing and sensor fusion, this can be a long and complex process. Signal Processing Signal processing is the next step in converting the MEMS signals to a sensible output. For motion tracking, the user is often interested in low-bandwidth signals. Yet, a high

bandwidth is required to compensate for vibrations and coning/sculling errors. A signal processing pipeline needs to be optimized for the anticipated motion. Also, since every MEMS sensor is different, the signal processing pipeline should be tailored to the specific MEMS sensor to make the best use of its capabilities. An incorrectly designed signal processing pipeline will negatively affect the performance of the module’s output. OS drivers and communication To communicate with the module, there needs to be drivers for the host, typically an application

New-Tech Magazine Europe l 49