{"product_id":"2126-lps331ap-pressure-altitude-sensor-carrier-with-voltage-regulator","title":"LPS331AP Pressure\/Altitude Sensor Carrier with Voltage Regulator","description":"\u003cp\u003eThis carrier for ST’s LPS331AP digital barometer measures pressures from 260 mbar to 1260 mbar (26 kPa to 126 kPa) with absolute pressure accuracy over temperature down to ±2 mbar (0.2 kPa) and typical RMS noise of 0.02 mbar (0.002 kPa) in high-resolution mode.  These pressures can easily be converted to altitudes.  The board has a 3.3 V linear regulator and integrated level shifters that allow it to work over an input voltage range of 2.5 V to 5.5 V, and the 0.1″ pin spacing makes it easy to use with standard solderless breadboards and 0.1″ perfboards.  The sensor offers I²C and SPI interfaces.\u003c\/p\u003e\n\u003cbr\u003e\u003ctable class=\"picture_with_caption right\"\u003e\u003ctr\u003e\n\u003ctd\u003e\u003ca href=\"https:\/\/a.pololu-files.com\/picture\/0J4422.1200.jpg?0bcb858bc8915543fee3e6306a49ca9c\" class=\"noscript-fallback\"\u003e\u003cimg alt=\"\" class=\"zoomable\" data-gallery-pictures=\"[{\" id pressure sensor carrier with voltage regulator bottom view dimensions. data-picture-id=\"0J4422\" data-picture-longest_side=\"409\" src=\"https:\/\/a.pololu-files.com\/picture\/0J4422.250.jpg?0bcb858bc8915543fee3e6306a49ca9c\"\u003e\u003c\/a\u003e\u003c\/td\u003e\n\u003cp\u003e\u003c\/p\u003e\n\u003c\/tr\u003e\u003c\/table\u003e\n\u003ch2\u003eOverview\u003c\/h2\u003e\n\u003cp\u003eThis board is a compact (0.4″ × 0.9″) carrier for ST’s LPS331AP MEMS absolute pressure sensor, or barometer; we therefore recommend careful reading of the \u003ca href=\"\/file\/0J622\/LPS331AP.pdf\"\u003eLPS331AP datasheet\u003c\/a\u003e (453k pdf) before using this product.  The LPS331 is a great IC, but its small, leadless, LGA package makes it difficult for the typical student or hobbyist to use.  It also operates at voltages below 3.6 V, which can make interfacing difficult for microcontrollers operating at 5 V.  This carrier board addresses these issues by incorporating additional electronics, including a 3.3 V voltage regulator and level-shifting circuits, while keeping the overall size as compact as possible.  The board ships fully populated with its SMD components, including the LPS331AP, as shown in the product picture.\u003c\/p\u003e\n\u003cp\u003eThe LPS331 features embedded temperature compensation and has many configurable options, including selectable resolutions, a choice of output data rates, and two programmable external interrupt signals.  Its pressure output has an absolute accuracy as low as ±2 mbar (0.2 kPa), with RMS noise of 0.02 mbar (0.002 kPa) in the highest-resolution mode. Pressure and temperature sensor data are available through a digital interface, which can be configured to operate in either I²C or SPI mode, and can be used for altimetry. (See the Sample Code section below for an Arduino library that can be used to turn this sensor into an altimeter).\u003c\/p\u003e\n\u003cp\u003eThe carrier board includes a low-dropout linear voltage regulator that provides the 3.3 V required by the LPS331, which allows the sensor to be powered from a 2.5 V to 5.5 V supply.  The regulator output is available on the VDD pin and can supply almost 150 mA to external devices. The breakout board also includes a circuit that shifts the I²C\/SPI clock and data in lines to the same logic voltage level as the supplied VIN, making it simple to interface the board with 5 V systems, and the board’s 0.1″ pin spacing makes it easy to use with standard \u003ca href=\"https:\/\/www.pololu.com\/category\/28\/solderless-breadboards\"\u003esolderless breadboards\u003c\/a\u003e and 0.1″ perfboards.\u003c\/p\u003e\n\u003cp\u003eFor sensor fusion applications, \u003ca href=\"https:\/\/www.pololu.com\/product\/2469\"\u003eAltIMU-10 v3\u003c\/a\u003e inertial measurement unit combines the LPS331AP with an \u003ca href=\"https:\/\/www.pololu.com\/product\/2129\"\u003eL3GD20H\u003c\/a\u003e 3-axis gyro and an \u003ca href=\"https:\/\/www.pololu.com\/product\/2127\"\u003eLSM303D\u003c\/a\u003e 3-axis accelerometer and 3-axis magnetometer on a single board, providing ten independent readings that can be used to calculate an absolute orientation and altitude.\u003c\/p\u003e\n\u003cp class=\"note\"\u003eThis module is a lower-cost alternative to our newer \u003ca href=\"https:\/\/www.pololu.com\/product\/2867\"\u003eLPS25HB carrier\u003c\/a\u003e, which offers improved accuracy, reduced output noise, and a built-in FIFO (First In, First Out) buffer allows the sensor to store pressure readings for burst transmission or to output a running average to further reduce output noise.\u003c\/p\u003e\n\u003ch3 class=\"clear\"\u003eSpecifications\u003c\/h3\u003e\n\u003cul\u003e\n\t\u003cli\u003eDimensions: 0.4″ × 0.9″ × 0.1″ (10 mm × 23 mm × 3 mm)\u003c\/li\u003e\n\t\u003cli\u003eWeight without header pins: 0.6 g (0.02 oz)\u003c\/li\u003e\n\t\u003cli\u003eOperating voltage: 2.5 V to 5.5 V\u003c\/li\u003e\n\t\u003cli\u003eSupply current: 2 mA\u003c\/li\u003e\n\t\u003cli\u003eOutput format (I²C\/SPI): 24-bit pressure reading (4096 LSb\/mbar)\u003c\/li\u003e\n\t\u003cli\u003eSensitivity range: 260 mbar to 1260 mbar (26 kPa to 126 kPa)\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eIncluded components\u003c\/h3\u003e\n\u003cp\u003eA 1×9 strip of \u003ca href=\"https:\/\/www.pololu.com\/product\/965\"\u003e0.1″ header pins\u003c\/a\u003e and a 1×9 strip of \u003ca href=\"https:\/\/www.pololu.com\/product\/967\"\u003e0.1″ right-angle header pins\u003c\/a\u003e are included, as shown in the picture below.  You can solder the header strip of your choice to the board for use with \u003ca href=\"https:\/\/www.pololu.com\/category\/70\/crimp-connector-housings\"\u003ecustom cables\u003c\/a\u003e or \u003ca href=\"https:\/\/www.pololu.com\/category\/28\/solderless-breadboards\"\u003esolderless breadboards\u003c\/a\u003e, or you can solder wires directly to the board itself for more compact installations.\u003c\/p\u003e\n\u003ctable class=\"picture_with_caption center\"\u003e\u003ctr\u003e\n\u003ctd\u003e\u003ca href=\"https:\/\/a.pololu-files.com\/picture\/0J4423.1200.jpg?9b3d382e969617de949f733d40b226bb\" class=\"noscript-fallback\"\u003e\u003cimg alt=\"\" class=\"zoomable\" data-gallery-pictures=\"[{\" id pressure sensor carrier with voltage regulator included optional headers. data-picture-id=\"0J4423\" data-picture-longest_side=\"800\" src=\"https:\/\/a.pololu-files.com\/picture\/0J4423.300.jpg?9b3d382e969617de949f733d40b226bb\"\u003e\u003c\/a\u003e\u003c\/td\u003e\n\u003cp\u003e\u003c\/p\u003e\n\u003c\/tr\u003e\u003c\/table\u003e\n\u003cp\u003eThe board has one mounting hole that works with #2 and M2 \u003ca href=\"https:\/\/www.pololu.com\/category\/101\/nuts-and-screws\"\u003escrews\u003c\/a\u003e (not included).\u003c\/p\u003e\n\u003ch2 class=\"clear\"\u003eUsing the LPS331\u003c\/h2\u003e\n\u003ch3\u003eConnections\u003c\/h3\u003e\n\u003cp\u003eRegardless of the interface being used to communicate with the LPS331AP, its VIN pin should be connected to a 2.5 V to 5.5 V source, and GND should be connected to 0 volts. (Alternatively, if you are using the sensor with a 3.3 V system, you can leave VIN disconnected and bypass the built-in regulator by connecting 3.3 V directly to VDD.)\u003c\/p\u003e\n\u003cp\u003eA minimum of two logic connections are necessary to use the LPS331 in I²C mode (this is the default mode): SCL and SDA.  These pins are connected to built-in level-shifters that make them safe to use at voltages over 3.3 V; they should be connected to an I²C bus operating at the same logic level as VIN.  The remaining pins are \u003cins\u003enot\u003c\/ins\u003e connected to level-shifters on the board and are \u003cins\u003enot\u003c\/ins\u003e 5V-tolerant, but our \u003ca href=\"https:\/\/www.pololu.com\/product\/2595\"\u003e4-channel bidirectional logic level shifter\u003c\/a\u003e can be used externally with those pins to achieve the same effect.\u003c\/p\u003e\n\u003cp\u003eTo use the LPS331 in the default SPI mode, four logic connections are required: SPC, SDI, SDO, and CS. These should be connected to an SPI bus operating at the same logic level as VIN. The SPI interface operates in 4-wire mode by default, with SDI and SDO on separate pins, but it can be configured to use 3-wire mode so that SDO shares a pin with SDI.\u003c\/p\u003e\n\u003ctable class=\"side_by_side_pics\"\u003e\n\t\u003ctr\u003e\n\t\t\u003ctd\u003e\u003ctable class=\"picture_with_caption center\"\u003e\n\u003ctr\u003e\u003ctd style=\"max-width: 325px\"\u003e\u003ca href=\"https:\/\/a.pololu-files.com\/picture\/0J4425.1200.jpg?2afd0b19d0d210c6e700e8d562d00e1e\" class=\"noscript-fallback\"\u003e\u003cimg alt=\"\" class=\"zoomable\" data-gallery-pictures=\"[{\" id pressure sensor carrier with voltage regulator labeled top view. data-picture-id=\"0J4425\" data-picture-longest_side=\"800\" src=\"https:\/\/a.pololu-files.com\/picture\/0J4425.325.jpg?2afd0b19d0d210c6e700e8d562d00e1e\"\u003e\u003c\/a\u003e\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003cth style=\"max-width: 325px\"\u003e\u003cp\u003eLPS331AP pressure\/altitude sensor carrier with voltage regulator, labeled top view.\u003c\/p\u003e\u003c\/th\u003e\u003c\/tr\u003e\n\u003c\/table\u003e\u003c\/td\u003e\n\t\t\u003ctd\u003e\u003ctable class=\"picture_with_caption center\"\u003e\n\u003ctr\u003e\u003ctd style=\"max-width: 300px\"\u003e\u003ca href=\"https:\/\/a.pololu-files.com\/picture\/0J4424.1200.jpg?3bbcf4fd208c9788f45b715440bc0342\" class=\"noscript-fallback\"\u003e\u003cimg alt=\"\" class=\"zoomable\" data-gallery-pictures=\"[{\" id pressure sensor carrier with voltage regulator in a breadboard. data-picture-id=\"0J4424\" data-picture-longest_side=\"800\" src=\"https:\/\/a.pololu-files.com\/picture\/0J4424.300.jpg?3bbcf4fd208c9788f45b715440bc0342\"\u003e\u003c\/a\u003e\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003cth style=\"max-width: 300px\"\u003e\u003cp\u003eLPS331AP pressure\/altitude sensor carrier with voltage regulator in a breadboard.\u003c\/p\u003e\u003c\/th\u003e\u003c\/tr\u003e\n\u003c\/table\u003e\u003c\/td\u003e\n\t\u003c\/tr\u003e\n\u003c\/table\u003e\n\u003ch3 class=\"clear\"\u003ePinout\u003c\/h3\u003e\n\u003ctable class=\"specifications center\"\u003e\n\t\u003ctr\u003e\n\t\t\u003cth\u003ePIN\u003c\/th\u003e\n\t\t\u003cth\u003eDescription\u003c\/th\u003e\n\t\u003c\/tr\u003e\n\t\u003ctr class=\"odd\"\u003e\n\t\t\u003ctd\u003eVDD\u003c\/td\u003e\n\t\t\u003ctd style=\"text-align:left;\"\u003eRegulated 3.3 V \u003cstrong\u003eoutput\u003c\/strong\u003e. Almost 150 mA is available to power external components. (If you want to bypass the internal regulator, you can instead use this pin as a 3.3 V input with VIN disconnected.)\u003c\/td\u003e\n\t\u003c\/tr\u003e\n\t\u003ctr\u003e\n\t\t\u003ctd\u003eVIN\u003c\/td\u003e\n\t\t\u003ctd style=\"text-align:left;\"\u003eThis is the main 2.5 V to 5.5 V power supply connection. The SCL\/SPC and SDA\/SDI level shifters pull the I²C and SPI bus high bits up to this level.\u003c\/td\u003e\n\t\u003c\/tr\u003e\n\t\u003ctr class=\"odd\"\u003e\n\t\t\u003ctd\u003eGND\u003c\/td\u003e\n\t\t\u003ctd style=\"text-align:left;\"\u003eThe ground (0 V) connection for your power supply.  Your I²C or SPI control source must also share a common ground with this board.\u003c\/td\u003e\n\t\u003c\/tr\u003e\n\t\u003ctr\u003e\n\t\t\u003ctd\u003eSDA\/SDI\/SDO\u003c\/td\u003e\n\t\t\u003ctd style=\"text-align:left;\"\u003eLevel-shifted I²C data line and SPI data in line (also doubles as SDO in 3-wire mode): HIGH is VIN, LOW is 0 V\u003c\/td\u003e\n\t\u003c\/tr\u003e\n\t\u003ctr class=\"odd\"\u003e\n\t\t\u003ctd\u003eSCL\/SPC\u003c\/td\u003e\n\t\t\u003ctd style=\"text-align:left;\"\u003eLevel-shifted I²C\/SPI clock line: HIGH is VIN, LOW is 0 V\u003c\/td\u003e\n\t\u003c\/tr\u003e\n\t\u003ctr\u003e\n\t\t\u003ctd\u003eSDO\/SA0\u003c\/td\u003e\n\t\t\u003ctd style=\"text-align:left;\"\u003eSPI data out line in 4-wire mode: HIGH is VDD, LOW is 0 V.  \u003cem\u003eThis output is not level-shifted.\u003c\/em\u003e Also used as an input to determine I²C slave address (see below).\u003c\/td\u003e\n\t\u003c\/tr\u003e\n\t\u003ctr class=\"odd\"\u003e\n\t\t\u003ctd\u003eCS\u003c\/td\u003e\n\t\t\u003ctd style=\"text-align:left;\"\u003eSPI enable (chip select). Pulled up to VDD to enable I²C communication by default; drive low to begin SPI communication.\u003c\/td\u003e\n\t\u003c\/tr\u003e\n\t\u003ctr\u003e\n\t\t\u003ctd\u003eINT2\u003c\/td\u003e\n\t\t\u003ctd style=\"text-align:left;\"\u003eProgrammable interrupt, a 3.3-V-logic-level output. \u003cem\u003eThis output is not level-shifted.\u003c\/em\u003e\n\u003c\/td\u003e\n\t\u003c\/tr\u003e\n\t\u003ctr class=\"odd\"\u003e\n\t\t\u003ctd\u003eINT1\u003c\/td\u003e\n\t\t\u003ctd style=\"text-align:left;\"\u003eProgrammable interrupt, a 3.3-V-logic-level output.  \u003cem\u003eThis output is not level-shifted.\u003c\/em\u003e\n\u003c\/td\u003e\n\t\u003c\/tr\u003e\n\u003c\/table\u003e\n\u003ch3\u003eSchematic diagram\u003c\/h3\u003e\n\u003ctable class=\"picture_with_caption center wide\"\u003e\u003ctr\u003e\n\u003ctd\u003e\u003cimg alt=\"\" class=\"wide\" data-gallery-pictures=\"[{\" id pressure sensor carrier with voltage regulator schematic diagram. data-picture-id=\"0J4420\" data-picture-longest_side=\"1023\" src=\"https:\/\/a.pololu-files.com\/picture\/0J4420.600.jpg?932ce7eeeeaa6e07a141c0ba4d44e3bc\"\u003e\u003c\/td\u003e\n\u003cp\u003e\u003c\/p\u003e\n\u003c\/tr\u003e\u003c\/table\u003e\n\u003cp\u003eThe above schematic shows the additional components the carrier board incorporates to make the LPS331AP easier to use, including the voltage regulator that allows the board to be powered from a 2.5 V to 5.5 V supply and the level-shifter circuit that allows for I²C and SPI communication at the same logic voltage level as VIN. This schematic is also available as a \u003ca href=\"\/file\/0J621\/lps331ap-pressure-altitude-sensor-carrier-with-voltage_regulator-schematic-diagram.pdf\"\u003edownloadable PDF\u003c\/a\u003e (156k pdf).\u003c\/p\u003e\n\u003ch3\u003eI²C communication\u003c\/h3\u003e\n\u003cp\u003eWith the CS pin in its default state (pulled up to VDD), the LPS331AP can be configured and its pressure reading can be queried through the I²C bus. Level shifters on the I²C clock (SCL) and data (SDA) lines enable I²C communication with microcontrollers operating at the same voltage as VIN (2.5 V to 5.5 V). A detailed explanation of the I²C interface on the LPS331 can be found in its \u003ca href=\"\/file\/0J622\/LPS331AP.pdf\"\u003edatasheet\u003c\/a\u003e (453k pdf), and more detailed information about I²C in general can be found in \u003ca href=\"\/file\/0J435\/UM10204.pdf\"\u003eNXP’s I²C-bus specification\u003c\/a\u003e (1MB pdf).\u003c\/p\u003e\n\u003cp\u003eIn I²C mode, the sensor’s 7-bit slave address has its least significant bit (LSb) determined by the voltage on the SA0 pin. The carrier board pulls SA0 to VDD through a 4.7 kΩ resistor, making the LSb 1 and setting the slave address to 1011101b by default. If the pressure sensor’s selected slave address happens to conflict with some other device on your I²C bus, you can drive SA0 low to set the LSb to 0.\u003c\/p\u003e\n\u003cp\u003eThe I²C interface on the LPS331 is compliant with the I²C fast mode (400 kHz) standard. In our tests of the board, we were able to communicate with the chip at clock frequencies up to 400 kHz; higher frequencies might work but were not tested. It is missing 50 ns spike suppression on the clock and data lines, and additional pull-ups on the clock and data lines might also be necessary to achieve compliant signal timing characteristics.\u003c\/p\u003e\n\u003ch3\u003eSPI communication\u003c\/h3\u003e\n\u003cp\u003eTo communicate with the LPS331AP in SPI mode, the CS pin (which the board pulls to VDD through a 4.7 kΩ resistor) must be driven low before the start of an SPI command and allowed to return high after the end of the command.  Level shifters on the SPI clock (SPC) and data in (SDI) lines enable SPI communication with microcontrollers operating at the same voltage as VIN (2.5 V to 5.5 V).\u003c\/p\u003e\n\u003cp\u003eIn the default 4-wire mode, the pressure sensor transmits data to the SPI master on a dedicated data out (SDO) line that is \u003cins\u003enot\u003c\/ins\u003e level-shifted. If the SPI interface is configured to use 3-wire mode instead, the SDI line doubles as SDO and is driven by the LPS331 when it transmits data to the master. A detailed explanation of the SPI interface on the LPS331 can be found in its \u003ca href=\"\/file\/0J622\/LPS331AP.pdf\"\u003edatasheet\u003c\/a\u003e (453k pdf).\u003c\/p\u003e\n\u003ch4\u003eSample code\u003c\/h4\u003e\n\u003cp\u003eWe have written a basic \u003ca href=\"https:\/\/github.com\/pololu\/lps-arduino\"\u003eArduino library for the LPS331\u003c\/a\u003e that makes it easy to interface this sensor with an \u003ca href=\"https:\/\/www.pololu.com\/product\/2191\"\u003eArduino\u003c\/a\u003e. The library makes it simple to configure the LPS331 and read the raw pressure data through I²C, and it provides functions for calculating altitude based on the measured pressure for those looking to use this sensor as an altimeter.\u003c\/p\u003e\n\u003ch3\u003eProtocol hints\u003c\/h3\u003e\n\u003cp\u003eThe datasheet provides all the information you need to use this sensor, but picking out the important details can take some time.  Here are some pointers for communicating with and configuring the LPS331AP that we hope will get you up and running a little bit faster:\u003c\/p\u003e\n\u003cul\u003e\n\t\u003cli\u003eThe pressure sensor is in power down mode by default. You have to turn it on by writing the appropriate value to the CTRL_REG1 register to choose an output data rate.\u003c\/li\u003e\n\t\u003cli\u003eYou can read or write multiple registers in a single I²C command by asserting the most significant bit of the register address to enable address auto-increment.\u003c\/li\u003e\n\t\u003cli\u003eYou can enable the same auto-increment feature in SPI mode by asserting the second bit (bit 1, called the M\u003cspan style=\"text-decoration:overline\"\u003eS\u003c\/span\u003e bit in the datasheet) of an SPI command.\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Pololu","offers":[{"title":"2-4 Settimane","offer_id":47696628973913,"sku":"POL-2126","price":5.78,"currency_code":"EUR","in_stock":true},{"title":"1 Giorno","offer_id":47885974995289,"sku":"POL-2126\/A","price":5.78,"currency_code":"EUR","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0781\/1009\/7753\/files\/0J4421.1200.jpg?v=1705455083","url":"https:\/\/robot-italy.com\/products\/2126-lps331ap-pressure-altitude-sensor-carrier-with-voltage-regulator","provider":"Robot Italy","version":"1.0","type":"link"}