The document provides an overview of the LIS331DLH MEMS digital output motion sensor from STMicroelectronics. It describes the sensor's key features such as wide voltage compatibility, low power modes, and integrated self-test. Applications include motion detection, free-fall detection, display orientation, and more. Block diagrams are shown of the sensor's architecture, interrupt generation, and SPI interface. A demonstration kit is also mentioned.
Welcome to the training module on An Overview Study of MEMS sensor Accelerometer.
This training module will introduce about basic working principle and other interfacing details of the MEMS device.
The LIS331DLH is an ultra low-power high performance three axes linear accelerometer belonging to the ânanoâ family, with digital I2C/SPI serial interface standard output. The device features ultra low-power operational modes that allow advanced power saving and smart sleep to wake-up functions. The LIS331DLH has dynamically user selectable full scales of ±2 g /±4 g /±8 g and it is capable of measuring accelerations with output data rates from 0.5 Hz to 1 kHz. The device may be configured to generate interrupt signal by inertial wake-up/free-fall events as well as by the position of the device itself
Low- g MEMS accelerometers are widely used for tilt sensing in consumer electronics and industrial applications, such as screen rotation and automobile security alert systems. Another popular application for low- g accelerometers is tilt compensated electronic compasses for map rotation and personal navigation devices.
Here is the block diagram of the LIS331.
This page gives information about the terminology for MEMS sensor like Sensitivity, Zero-g level, Sleep to wake-up.
The ultra-low power LIS331DLH digital accelerometer is housed in a 3 x 3 x 1 mm LGA-16 package. It has an I2C / SPI digital serial interface for 3-axis acceleration outputs, so no external ADC chip is required. It also features a dynamically user-selectable full-scale measurement range of ±2 g / ±4 g / ±8 g , with output data rates from 0.5 Hz to 1 kHz. The LIS331DLH, have been factory calibrated.
The device has two pins which can be activated to generate either the data-ready signal or the interrupt signal. The functionality of the pins is selected acting on bit I1(2)_CFGx bits of the CTRL_REG3 register. the data-ready (DR) signal rises to 1 when a new set of acceleration data has been generated and is available for reading. The signal is reset after all the enabled channels are read through the serial interface.
The LIS331DLH can operate in the following four modes, which can be selected through the configuration of CTR_REG1 and CTRL_REG5. the PowerMode (PM) and DataRate (DR) bits of CTRL_REG1 register are used to select the basic operating modes (Power Down, Normal mode and Low Power). The TurnOn bits of the CTRL_REG5 register are used to enable Sleep to Wake, which is an advanced mode involving the interrupt configuration In Normal mode, data are generated at the data rate (ODR) selected through the DR bits and for the axis enabled through the Zen, Yen and Xen bits of the CTRL_REG1 register. Data generated for a disabled axis is 00h. in Power Down mode, almost all internal blocks of the device are switched off to minimize power consumption
The LIS331DLH provides embedded high-pass filtering capability to easily remove the DC component of the measured acceleration. It is possible to independently apply the filter on the output data and/or on the interrupts data through the FDS, HPen1 and HPen2 bits of the CTRL_REG2 register configuration.
The LIS331DLH interrupt signals can behave as free-fall, wake-up or 6D orientation detection. When an interrupt condition is verified, the interrupt signal is generated and by reading the INT1_SRC and INT2_SRC registers it is possible to determine which condition has occurred. FF or WU interrupt generation is selected through the AOI bit in INTx_CFG register. If the AOI bit is â0â, signals coming from comparators are put in logical âORâ when an interrupt condition is applied, the interrupt signal remains high even if the condition returns to a non-interrupt status, until a reading of the INTx_SRC register is performed
The LIS331DLH SPI is a bus slave. The SPI allows to write and read the registers of the device. The Serial Interface interacts with the outside world with 4 wires: CS , SPC , SDI and SDO . CS is the serial port enable and it is controlled by the SPI master. It goes low at the start of the transmission and goes back high at the end. SPC is the serial port clock and it is controlled by the SPI master. It is stopped high when CS is high (no transmission). SDI and SDO are respectively the serial port data input and output. Those lines are driven at the falling edge of SPC and should be captured at the rising edge of SPC . The SPI Read command is performed with 16 clock pulses. Multiple byte read command is performed adding blocks of 8 clock pulses at the previous one.
The ST7-USB microcontroller included on the board allows communication between the sensor device and the PC. The user can interact with the hardware through the GUI provided with the kit. It requires the installation of a dedicated driver which is included in the installation pack, together with a GUI interface which allows simple interaction with the sensor.
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