An Overview Study on MEMS digital output motion sensor: LIS331DLH


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An Overview Study on MEMS digital output motion sensor: LIS331DLH

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  • 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 “nano” 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 ‘0’, signals coming from comparators are put in logical “OR” 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.
  • Thank you for taking the time to view this presentation on “ An Overview Study of MEMS sensor: Accelerometer” . If you would like to learn more or go on to purchase some of these devices, you may either click on the part list link right beside the play button on the TechCast portal, or simply call our sales hotline. For more technical information you may either visit the STMicroelectronics site, or if you would prefer to speak to someone live, please call our hotline number, or use our ‘live chat’ online facility. You may visit element14 e-community to post your questions.
  • An Overview Study on MEMS digital output motion sensor: LIS331DLH

    1. 1. An Overview Study on MEMS digital output motion sensor: LIS331DLH <ul><li>Source: STMicroelectronics </li></ul>
    2. 2. Introduction <ul><li>Purpose </li></ul><ul><ul><li>An Overview Study on MEMS digital output motion sensor: LIS331DLH </li></ul></ul><ul><li>Outline </li></ul><ul><ul><li>Features and Application of MEMS device </li></ul></ul><ul><ul><li>Block Diagram and Terminology </li></ul></ul><ul><ul><li>Tilt Measurement using accelerometer </li></ul></ul><ul><ul><li>Block diagram of Interrupt and Data Ready signal </li></ul></ul><ul><ul><li>operating mode, High Pass Filter, SPI bus Interface </li></ul></ul><ul><ul><li>Demo Kit Details </li></ul></ul><ul><li>Content </li></ul><ul><ul><li>14 pages </li></ul></ul>
    3. 3. Features <ul><li>■ Wide supply voltage, 2.16 V to 3.6 V </li></ul><ul><li>■ Low voltage compatible IOs, 1.8 V </li></ul><ul><li>■ Ultra low-power mode consumption down to 10 μA </li></ul><ul><li>■ ±2 g /±4 g /±8 g dynamically selectable full-scale </li></ul><ul><li>■ I2C/SPI digital output interface </li></ul><ul><li>■ 16 bit data output </li></ul><ul><li>■ 2 independent programmable interrupt generators for free-fall and </li></ul><ul><li>motion detection </li></ul><ul><li>■ Sleep to wake-up function </li></ul><ul><li>■ 6D orientation detection </li></ul><ul><li>■ Embedded self-test </li></ul><ul><li>■ 10000 g high shock survivability </li></ul><ul><li>■ ECOPACK® RoHS and “Green” compliant </li></ul>
    4. 4. Applications <ul><li>■ Motion activated functions </li></ul><ul><li>■ Free-fall detection </li></ul><ul><li>■ Intelligent power saving for handheld devices </li></ul><ul><li>■ Pedometer </li></ul><ul><li>■ Display orientation </li></ul><ul><li>■ Gaming and virtual reality input devices </li></ul><ul><li>■ Impact recognition and logging </li></ul><ul><li>■ Vibration monitoring and compensation </li></ul>
    5. 5. Block Diagram
    6. 6. Terminology <ul><li>Sensitivity </li></ul><ul><li>Sensitivity describes the gain of the sensor </li></ul><ul><li>Its value changes very little over temperature and also time </li></ul><ul><li>As the sensor can measure DC accelerations this can be done easily by pointing the axis of interest towards the centre of the earth </li></ul><ul><li>Zero-g level </li></ul><ul><li>Zero- g level offset (TyOff) describes the deviation of an actual output signal from the ideal output signal if no acceleration is present </li></ul><ul><li>A sensor in a steady state on a horizontal surface will measure 0 g in X axis and 0 g in Y axis whereas the Z axis will measure 1 g </li></ul><ul><li>Sleep to wake-up </li></ul><ul><li>The “sleep to wake-up” function, in conjunction with low-power mode, allows to further reduce the system power consumption and develop new smart applications </li></ul><ul><li>LIS331DLH may be set in a low-power operating mode, characterized by lower date rates refreshments. </li></ul>
    7. 7. Tilt measurement using a low- g 3-axis accelerometer <ul><li>Xb, Yb and Zb are the handheld device body axes with a forward-right-down configuration </li></ul><ul><li>XA, YA and ZA are the accelerometer sensing axes </li></ul><ul><li>Pitch and roll angles are referenced to the local horizontal plane, which is perpendicular to the Earth's gravity </li></ul><ul><li>Pitch (α) is defined as the angle between the Xb axis and the horizontal plane </li></ul><ul><li>Roll (β) is defined as the angle between the Yb axis and the horizontal plane </li></ul>
    8. 8. Interrupt and Data Ready signal generation block diagram
    9. 9. Operating modes <ul><li>● Normal mode </li></ul><ul><li>● Power down </li></ul><ul><li>● Low power </li></ul><ul><li>● Sleep to wake </li></ul>
    10. 10. High Pass Filter
    11. 11. Free-fall and wake-up Interrupts
    12. 12. SPI Bus Interface SPI read protocol SPI write protocol
    13. 13. Demonstration kit STEVAL-MKI022V1 <ul><li>The LIS331DLH is a low-power 3-axis linear accelerometer with digital output </li></ul><ul><li>The device includes a sensing </li></ul><ul><li>element and an IC interface capable of translating information from the sensing element into a measured signal </li></ul>
    14. 14. Additional Resource <ul><li>For ordering LIS331XX, please click the part list or </li></ul><ul><li>Call our sales hotline </li></ul><ul><li>For more product information go to </li></ul><ul><ul><li> </li></ul></ul><ul><li>Visit element14 to post your question </li></ul><ul><ul><li> </li></ul></ul><ul><li>For additional inquires contact our technical service hotline or even use our “Live Technical Chat” online facility </li></ul>