SparkFun Absolute Digital Barometer - LPS28DFW (Qwiic) Hookup Guide

2023-02-28 | By SparkFun Electronics

License: See Original Project Environmental Qwiic

Courtesy of SparkFun

Guide by EL DUDERINO

Introduction

The SparkFun Absolute Digital Barometer - LPS28DFW (Qwiic) (Standard Size and Micro Size) ‎offer a unique barometer breakout featuring the LPS28DFW from STMicroelectronics^©. The ‎LPS28DFW is an absolute barometer with a water-resistant package making it perfect for pressure ‎measurement applications where the sensor is exposed to or even submerged in water¹.‎

SparkFun Absolute Digital Barometer - LPS28DFW (Qwiic)‎

SparkFun Micro Absolute Digital Barometer - LPS28DFW ‎‎(Qwiic)‎

The sensor has two full-scale measurement ranges of 260 - 1260hPa and 260 - 4060hPa with an ‎absolute pressure accuracy of 0.5hPa. The LPS28DFW is composed a piezoresistive pressure ‎sensor with a metal lid and gel encasing to protect the sensing elements from water and other ‎environmental hazards.‎

In this guide we'll cover the features and specifications of the LPS28DFW and other hardware ‎present on these Qwiic breakouts as well as the Arduino library we have written to interact with the ‎sensor.‎

‎1. Important! While the LPS28DFW is protected from water, the rest of the components on these ‎breakouts are not protected by any conformal coating and can be damaged by exposure to liquids. ‎Users who intend to use these breakouts in applications where the board may be exposed to water, ‎or other liquids should apply conformal coating to the board prior to use.‎

Required Materials

To follow along with this guide, you will need a microcontroller to communicate with the LPS28DFW. ‎Below are a few options that come Qwiic-enabled out of the box:‎

If your chosen microcontroller is not already Qwiic-enabled, you can add that functionality with one ‎or more of the following items:‎

You will also need at least one Qwiic cable to connect the breakout to your microcontroller.‎

Suggested Reading

If you aren't familiar with the Qwiic system, we recommend reading here for an overview.‎

qwiic_1

We would also recommend taking a look at the following tutorials if you aren't familiar with the ‎concepts covered in them. If you are using one of the Qwiic Shields listed above, you may want to ‎read through their respective Hookup Guides as well before you get started with the SparkFun ‎Absolute Digital Barometer - LPS28DFW (Qwiic).‎

I2C: An introduction to I2C, one of the main embedded communications protocols in use today.‎
Serial Terminal Basics: This tutorial will show you how to communicate with your serial devices ‎using a variety of terminal emulator applications.‎
Qwiic Shield for Arduino & Photon Hookup Guide: Get started with our Qwiic ‎ecosystem with the Qwiic shield for Arduino or Photon.‎
SparkFun Qwiic Shield for Arduino Nano Hookup Guide: Hookup Guide for the ‎SparkFun Qwiic Shield for Arduino Nano.‎

Hardware Overview

In this section we'll take a closer look at the LPS28DFW and other hardware on these Qwiic ‎breakouts.‎

LPS28DFW Absolute Pressure Sensor

The LPS28DFW from STMicroelectronics is a digital output absolute pressure sensor with a gel-‎filled metal lid protecting the sensing element from moisture making it ideal for applications such as ‎water depth measurements or other pressure-sensing projects in wet environments.‎

sensor_2

The LPS28DFW has two user-selectable measurement ranges (260 to 1260hPa and 260 to ‎‎4060hPa) with an absolute pressure accuracy of 0.5hPa and supports output data rates of 1 to ‎‎200Hz. The sensor supports communication over I²C and MIPI I3C^SM interfaces (though I3C ‎communication is not covered in this guide or the Arduino Library). The table below outlines some ‎of the parameters for the LPS28DFW. For a complete overview of the sensor, refer to ‎the datasheet.‎

table_3

I²C Interface

The standard size routes the I²C interface to a pair of Qwiic connectors as well as a 0.1"-spaced ‎PTH header for users who prefer a traditional soldered connection. Both breakouts route the ‎sensor's interrupt (INT) pin to a PTH pin.‎

interface_4

Both boards set the LPS28DFW's I²C address to 0x5C by default. Adjust the ADR jumper to change ‎to the alternate address (0x5D) or open it completely to toggle the address using the ADR PTH pin ‎‎(Standard size only). More information on this jumper in the Solder Jumpers section below.‎

Solder Jumpers

Both LPS28DFW Qwiic breakouts have three solder jumpers labeled: PWR, I2C, and ADR. The ‎table below outlines the jumpers' label, default state, function, and any notes about their behavior.‎

jumpers_5 ‎

table__6

Board Dimensions

The boards match the Standard and Micro form-factors for Qwiic breakouts measuring 1" x 1" ‎‎(Standard) and 0.5" x 0.3" (Micro). The Standard breakout has four mounting holes, and the Micro ‎has one. All mounting holes fit a size 4-40 screw.‎

dimensions_7

dimensions_7a

‎Hardware Assembly

Now that we're familiar with the LPS28DFW breakouts, we can start assembling our circuit.‎

Qwiic/I²C Assembly

The fastest and easiest way to get started using the breakouts is to connect the Qwiic connector on ‎the breakout to a Qwiic-enabled development board like the SparkFun RedBoard Artemis with a ‎Qwiic cable and as shown in the image below.‎

assembly_8

If you would prefer a more secure and permanent connection with the Standard Size breakout, you ‎can solder headers or wire to the PTH header on the board.‎

Conformal Coating for Waterproofing

While the LPS28DFW's gel filled cap protects the sensing element from liquid and other ‎environmental effects, the breakouts do not have any coating to protect the other components from ‎damage due to exposure to liquids. A protective coating is required for applications that expose the ‎board(s) to liquid. This tutorial on customizing LilyPad LED colors has tips on how to apply a ‎conformal coating.‎

LPS28DFW Arduino Library

Note: This library assumes you are using the latest version of the Arduino IDE on your desktop. If ‎this is your first time using Arduino, please review our tutorial on installing the Arduino IDE. If you ‎have not previously installed an Arduino library, please check out our installation guide.‎

The SparkFun LPS28DFW Arduino Library provides a quick and easy way to get started configuring ‎and measuring pressure data from the sensor. Install the library using the Arduino Library Manager ‎tool by searching for "SparkFun LPS28DFW". Users who prefer to manually install the library can ‎download a copy of it from the GitHub repository by clicking the button below:‎

SPARKFUN LPS28DFW ARDUINO LIBRARY

Library Functions

The list below outlines and describes the functions available in the SparkFun LPS28DFW Arduino ‎Library. For detailed information on the parameters and use of all functions, refer to the .cpp file in ‎the library.‎

Device Initialization and Configuration

‎'int32_t begin(uint8_t address = LPS28DFW_I2C_ADDRESS_DEFAULT, TwoWire& wirePort ‎‎= Wire);' - Begin communication with the sensor over I² at the defined address and on the ‎defined port. If no error occur, perform a soft reset and initialize the sensor
‎'int32_t init();' - Enables the BDU and IF_ADD_INC bits in the control registers
‎'int32_t boot();' - Enables the BOOT bit in the control registers
‎'int32_t reset();' - Resets the sensor
‎'int32_t setModeConfig(lps28dfw_md_t* mode);' - Configures the operation mode settings for ‎the sensor including range and ODR
‎'int32_t getModeConfig(lps28dfw_md_t* mode);' - Returns the operation mode settings
‎'int32_t getStatus(lps28dfw_stat_t* status);' - Returns the sensor status bits such as data ‎ready, overrun, etc

Sensor Data

‎'int32_t getSensorData();' - Get pressure data from the sensor

Interrupt Control and Feature Selection

‎'int32_t setInterruptMode(lps28dfw_int_mode_t* intMode);' - Configures the interrupt pin to ‎be either HIGH/LOW and LATCHED/PULSED
‎'int32_t enableInterrupts(lps28dfw_pin_int_route_t* intRoute);' - Enables the data ready and ‎FIFO interrupt conditions
‎'int32_t getInterruptStatus(lps28dfw_all_sources_t* status);' - Returns the status of the ‎interrupt flags

FIFO Buffer Control

‎'int32_t setFIFOConfig(lps28dfw_fifo_md_t* fifoConfig);' - Sets the FIFO configuration ‎parameters
‎'int32_t getFIFOConfig(lps28dfw_fifo_md_t* fifoConfig);' - Returns settigs of FIFO buffer
‎'int32_t getFIFOLength(uint8_t* numData);' - Returns the number of samples stored in the ‎FIFO buffer (up to 128)
‎'int32_t getFIFOData(lps28dfw_fifo_data_t* data, uint8_t numData);' - Gets pressure data from ‎the FIFO buffer
‎'int32_t flushFIFO();' - Clear all data from the FIFO buffer

Reference Mode Control

‎'int32_t setReferenceMode(lps28dfw_ref_md_t* mode);' - Sets the sensor to operate in ‎reference mode. When called it stores the latest pressure data as a reference pressure. The ‎reference pressure can be used with Threshold Mode to trigger interrupts
‎'int32_t setThresholdMode(lps28dfw_int_th_md_t* mode);' - Configures the sensor to trigger ‎interrupts when the pressure measured exceeds a threshold relative to the defined reference ‎pressure
‎'int32_t getReferencePressure(int16_t* pressRaw);' - Returns the value stored for the ‎reference pressure

Arduino Examples

Now let's take a closer look at a few of the examples included in the LPS28DFW Arduino Library.‎

Example 1 - Basic Readings

The first example covers the basics of polling the LPS28DFW for pressure and temperature data ‎over I²C. Open the example by navigating to File > Examples > SparkFun LPS28DFW Arduino ‎Library > Example1_BasicReadings. Select your Board and Port and click the Upload button. ‎Once upload completes, open the serial monitor with the baud set to 115200 and watch pressure ‎and temperature data print out.‎

The code assumes the sensor uses the default I²C address so if you have adjusted the ADR jumper ‎to switch to the alternate address, comment/uncomment the line with the correct value listed:‎

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uint8_t i2cAddress = LPS28DFW_I2C_ADDRESS_DEFAULT; // 0x5C
//uint8_t i2cAddress = LPS28DFW_I2C_ADDRESS_SECONDARY; // 0x5D

The example attempts to initialize the sensor with default settings in I²C at the specified address. If ‎it cannot initialize properly, the code prints out an error in over serial:‎

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while(pressureSensor.begin(i2cAddress) != LPS28DFW_OK)
    {
        // Not connected, inform user
        Serial.println("Error: LPS28DFW not connected, check wiring and I2C address!");

        // Wait a bit to see if connection is established
        delay(1000);
    }

If you see this error, double check the sensor is connected properly and set to the correct I²C ‎address and reset the development board or re-upload the code.‎

The main loop gets temperature and pressure data measurements from the sensor every second:‎

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{
    // Get measurements from the sensor. This must be called before accessing
    // the pressure data, otherwise it will never update
    pressureSensor.getSensorData();

    // Print temperature and pressure
    Serial.print("Temperature (C): ");
    Serial.print(pressureSensor.data.heat.deg_c);
    Serial.print("\t\t");
    Serial.print("Pressure (hPa): ");
    Serial.println(pressureSensor.data.pressure.hpa);

    // Only print every second
    delay(1000);
}

Try moving the sensor up and down to see the pressure data change.‎

Example 3 - Interrupts

Example 3 shows how to set up and use data ready interrupts triggered by the sensor. The code ‎defaults to use D2 as the interrupt pin on a connected development board. If your board does not ‎support external interrupts on D2, adjust this line:‎

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int interruptPin = 2

If you're not sure which pins on your development board support external interrupts, this reference ‎page lists usable digital pins for most common Arduino development boards.‎

After initializing the LPS28DFW, the code sets the ODR to 1Hz, configures the interrupt pin to ‎operate in Data Ready mode and attaches the interrupt to the pin defined above (D2:‎

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ps28dfw_md_t modeConfig =
    {
        .fs  = LPS28DFW_1260hPa,    // Full scale range
        .odr = LPS28DFW_1Hz,        // Output data rate
        .avg = LPS28DFW_4_AVG,      // Average filter
        .lpf = LPS28DFW_LPF_DISABLE // Low-pass filter
    };
    pressureSensor.setModeConfig(&modeConfig);

    // Configure the LPS28DFW interrupt pin mode
    lps28dfw_int_mode_t intMode =
    {
        .int_latched  = 0, // Latching mode (not including data ready condition)
        .active_low   = 1, // Signal polarity
        .drdy_latched = 0  // Latching mode (data ready condition only)
    };
    pressureSensor.setInterruptMode(&intMode);

    // Configure the LPS28DFW to trigger interrupts when measurements finish
    lps28dfw_pin_int_route_t intRoute =
    {
        .drdy_pres = 1, // Trigger interrupts when measurements finish
        .fifo_th   = 0, // Trigger interrupts when FIFO threshold is reached
        .fifo_ovr  = 0, // Trigger interrupts when FIFO overrun occurs
        .fifo_full = 0  // Trigger interrupts when FIFO is full
    };
    pressureSensor.enableInterrupts(&intRoute);

    // Setup interrupt handler
    attachInterrupt(digitalPinToInterrupt(interruptPin), lps28dfwInterruptHandler, RISING);
}

The main loop waits for a Data Ready interrupt event to occur and then prints out the data from the ‎sensor over serial.‎

Example 5 - Reference Mode

Example 5 demonstrates how to set and use reference measurements to trigger interrupts from the ‎LPS28DFW. Reference mode allows you to store a pressure value as a reference and then monitor ‎the sensor's output to trigger an interrupt if it goes above or below the threshold value by a ‎specified amount.‎

The reference value register is READ only so we cannot manually set the threshold value in the ‎code. Instead, the code waits for the user to input they are ready to set the threshold value and ‎then enter any key to trigger the event.‎

The code sets the over and under pressure thresholds to 1hPa above/below the stored reference ‎pressure. If you want to adjust it, change the settings here:‎

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lps28dfw_int_th_md_t thresholdMode =
    {
        .threshold = 16, // Threshold above/below the reference pressure (eg. 16 = 1hPa in 1260hPa range)
        .over_th = true, // Enable the "over pressure" interrupt condition
        .under_th = true // Enable the "under pressure" interrupt condition
    };
    pressureSensor.setThresholdMode(&thresholdMode);

Note, the threshold value must be set in multiples of 16 when in Mode 1 (260-1260hPa) and ‎multiples of 8 when in Mode 2 (260-4060hPa). For example, to set the pressure threshold to ‎above/below 1hPa, set the .threshold to 16.‎

After uploading, open the serial monitor with the baud set to 115200 and get the sensor ready to ‎take the threshold measurement. Wait for the prompt and press any key to set the value. If ‎successful, you should see the serial printout below:‎

com4_9

Once the threshold is set, the main loop prints out temperature and pressure data and waits for an ‎interrupt event to trigger if the pressure readings go above or below the threshold pressure by ‎‎1hPa.‎

Troubleshooting

Waterproofing the Breakouts

As mentioned previously, these breakouts do not have any coating on them to protect the ‎components from water damage so users who intend to take advantage of the LPS28DFW's water ‎resistant design will need to coat the breakout in a waterproof coating such as conformal coating. ‎This tutorial on customizing LilyPad LED colors has tips on how to apply a conformal coating.‎

Pressure Data as Altitude

If you want to use the pressure data from the LSP28DFW to determine the altitude of the sensor, ‎refer to this section of our MPL3115A2 Breakout Hookup Guide for more information on how to ‎manipulate and correctly interpret pressure data.‎

General Troubleshooting

Not working as expected and need help?

If you need technical assistance and more information on a product that is not working as you ‎expected, we recommend heading on over to the SparkFun Technical Assistance page for some ‎initial troubleshooting.

SPARKFUN TECHNICAL ASSISTANCE PAGE‎ ‎

If you don't find what you need there, the SparkFun Forums are a great place to find and ask for ‎help. If this is your first visit, you'll need to create a Forum Account to search product forums and ‎post questions.

CREATE NEW FORUM ACCOUNT LOG INTO SPARKFUN FORUMS

Resources and Going Further

That's a wrap for this hookup guide. At this point you should have your breakout up and running ‎returning pressure data over I²C. Check out the resources below for more information on the ‎breakouts and the LPS28DFW:‎