Wiring the ST LPS25HB / LPS331AP Pressure, Barometer MEMS Sensor

This is the LPS25HB release by STMicroelectronics. The LPS25HB is an absolute pressure sensor with a feature that functions as a digital output barometer that rages from 260 mbar to 1260 mbar 26 kPa to 126 kPa with absolute accuracy down to ±0.2 mbar and typical RMS (Root Mean Square) noise of 0.01 mbar in high resolution these pressures can easily be transformed to altitudes. As you can see in the circuit diagram it has a 3.3v LDO Linear Regulator and pullup resistors this will allows you to work over an input voltage range of 2.5v to 5.5v and communicates on i2C / TWI and SPI bus. ST’s LPS25HB a MEMS (Microelectromechanical System) an absolute pressure, barometer sensor a small leadless, land grid array package that makes it difficult to wire directly to your microcontroller. However, you can use an LGA / SMD adapter or use our PCB milling file below.

The LPS25HB & LPS331AP pressure and barometer use the same i2C address bus, but different registers field, these IC has embedded temperature compensation with a set of various configuration options, including selectable resolutions, output data rates, FIFO operating modes, and programmable external interrupt signal. This pressure has an absolute pressure accuracy over temperatures as low as ±0.2 mbar with RMS (Root Mean Square) noise of 0.01 mbar at the highest resolution mode with enabled integrated filtering. This pressure and temperature sensor are available through a digital interface. before proceeding to use this sensor please read carefully the LPS25HB / LPS331AP Datasheet.

Requirements

Arduino IDE | PlatformIO
Test Boards :
- Note: The Diagram below is using Raspberry Pi PICO (please refer to your MCU’s respective pin-outs & bus configuration)
Resistors (See below diagram for required value)
Regulator (3.3V LDO)
Capacitor(See below diagram for required value)

Wiring Diagram / Schematics

LPS25HB Sketch Source Code

#include <Wire.h>
#include <LPS.h>
LPS ps; //Initialize i2C 
void setup()
{
  Serial.begin(9600);
  Serial.print("14CORE | TEST LPS25HB / LPS331AP");
  delay(2000);
  Wire.begin();
  Serial.print("Initializing .................. ");
  if (!ps.init())
  {
    Serial.println("Error: Failed to read pressure sensor!");
    while (1);
  }

  ps.enableDefault();
}

void loop()
{
  float pressure = ps.readPressureMillibars();
  float altitude = ps.pressureToAltitudeMeters(pressure);
  float temperature = ps.readTemperatureC();
  Serial.print("p: ");
  Serial.print(pressure);
  Serial.print(" mbar\ta: ");
  Serial.print(altitude);
  Serial.print(" m\tt: ");
  Serial.print(temperature);
  Serial.println(" deg C");
  delay(100);
}

#include <Wire.h>

#include <LPS.h>

LPS ps; //Initialize i2C

void setup()

{

Serial.begin(9600);

Serial.print("14CORE | TEST LPS25HB / LPS331AP");

delay(2000);

Wire.begin();

Serial.print("Initializing .................. ");

if (!ps.init())

{

Serial.println("Error: Failed to read pressure sensor!");

while (1);

}

ps.enableDefault();

}

void loop()

{

float pressure = ps.readPressureMillibars();

float altitude = ps.pressureToAltitudeMeters(pressure);

float temperature = ps.readTemperatureC();

Serial.print("p: ");

Serial.print(pressure);

Serial.print(" mbar\ta: ");

Serial.print(altitude);

Serial.print(" m\tt: ");

Serial.print(temperature);

Serial.println(" deg C");

delay(100);

}

LPS25HB Sketch Code w/o Library

#include<Wire.h>

// LPS25HB I2C address is 0x5C(92)
#define Addr 0x5C

void setup() 
{
  // Initialise I2C communication as MASTER 
  Wire.begin();
  // Initialise Serial communication, set baud rate = 9600
  Serial.begin(9600);

  // Start I2C Transmission
  Wire.beginTransmission(Addr);
  // Select control register 1
  Wire.write(0x20);
  // Set active mode, continuous Update
  Wire.write(0x90);
  // Stop I2C Transmission
  Wire.endTransmission();
  delay(300); 
}

void loop()
{
  unsigned int data[3];
  // Start I2C Transmission
  Wire.beginTransmission(Addr);
  // Select pressure data register
  Wire.write(0x28 | 0x80);
  // Stop I2C Transmission
  Wire.endTransmission();
  
  // Request 3 bytes of data
  Wire.requestFrom(Addr, 3);

  // Read 3 bytes of data
  // pressure lsb first
  if(Wire.available() == 3)
  {
    data[0] = Wire.read();
    data[1] = Wire.read();
    data[2] = Wire.read();
  }
  delay(300);
    
  // Convert pressure data
  float pressure = ((data[2] * 65536) + (data[1] * 256) + data[0]) / 4096.0;
  
  // Output data to serial monitor
  Serial.print("Pressure is : ");
  Serial.print(pressure);
  Serial.println(" hPa"); 
  delay(1000);
}

#include<Wire.h>

// LPS25HB I2C address is 0x5C(92)

#define Addr 0x5C

void setup()

{

// Initialise I2C communication as MASTER

Wire.begin();

// Initialise Serial communication, set baud rate = 9600

Serial.begin(9600);

// Start I2C Transmission

Wire.beginTransmission(Addr);

// Select control register 1

Wire.write(0x20);

// Set active mode, continuous Update

Wire.write(0x90);

// Stop I2C Transmission

Wire.endTransmission();

delay(300);

}

void loop()

{

unsigned int data[3];

// Start I2C Transmission

Wire.beginTransmission(Addr);

// Select pressure data register

Wire.write(0x28 | 0x80);

// Stop I2C Transmission

Wire.endTransmission();

// Request 3 bytes of data

Wire.requestFrom(Addr, 3);

// Read 3 bytes of data

// pressure lsb first

if(Wire.available() == 3)

{

data[0] = Wire.read();

data[1] = Wire.read();

data[2] = Wire.read();

}

delay(300);

// Convert pressure data

float pressure = ((data[2] * 65536) + (data[1] * 256) + data[0]) / 4096.0;

// Output data to serial monitor

Serial.print("Pressure is : ");

Serial.print(pressure);

Serial.println(" hPa");

delay(1000);

}

LPS25HB Java Source Code

Get the Java /PI4J Library here

import com.pi4j.io.i2c.I2CBus;
import com.pi4j.io.i2c.I2CDevice;
import com.pi4j.io.i2c.I2CFactory;
import java.io.IOException;

public class LPS25HB
{
	public static void main(String args[]) throws Exception
	{
		// Create I2C bus
		I2CBus bus = I2CFactory.getInstance(I2CBus.BUS_1);
		// Get I2C device, LPS25HB I2C address is 0x5C(72)
		I2CDevice device = bus.getDevice(0x5C);
		
		// Active mode, Continuous Update
		device.write(0x20, (byte)0x90);
		Thread.sleep(500);
		
		// Read 3 bytes of data from address 0x28(40), lsb first
		byte[] data = new byte[3];
		device.read(0x28 | 0x80, data, 0, 3);
		
		// Convert data to hPa
		double pressure = (((data[2] & 0xff) * 65536) + ((data[1] & 0xff) * 256) + (data[0] & 0xff)) / 4096.0;
		
		// Output to the screen
		System.out.printf("Pressure is : %.2f hPa %n", pressure);
	}
}

import com.pi4j.io.i2c.I2CBus;

import com.pi4j.io.i2c.I2CDevice;

import com.pi4j.io.i2c.I2CFactory;

import java.io.IOException;

public class LPS25HB

{

public static void main(String args[]) throws Exception

{

// Create I2C bus

I2CBus bus = I2CFactory.getInstance(I2CBus.BUS_1);

// Get I2C device, LPS25HB I2C address is 0x5C(72)

I2CDevice device = bus.getDevice(0x5C);

// Active mode, Continuous Update

device.write(0x20, (byte)0x90);

Thread.sleep(500);

// Read 3 bytes of data from address 0x28(40), lsb first

byte[] data = new byte[3];

device.read(0x28 | 0x80, data, 0, 3);

// Convert data to hPa

double pressure = (((data[2] & 0xff) * 65536) + ((data[1] & 0xff) * 256) + (data[0] & 0xff)) / 4096.0;

// Output to the screen

System.out.printf("Pressure is : %.2f hPa %n", pressure);

}

LPS25HB MicroPython Code

MicroPython Download Library Here

import smbus
import time

# Get I2C bus
bus = smbus.SMBus(1)

# LPS25HB address, 0x5C(92)
# Select Control register, 0x20(32)
#		0x90(144)	Active mode, Continous update
bus.write_byte_data(0x5C, 0x20, 0x90)

time.sleep(0.1)

# LPS25HB address, 0x5C(92)
# Read data back from 0x28(40), with Command register, 0x80(128)
# 3 bytes, Pressure LSB first
data = bus.read_i2c_block_data(0x5C, 0x28 | 0x80, 3)

# Convert the data to hPa
pressure = (data[2] * 65536 + data[1] * 256 + data[0]) / 4096.0

# Output data to screen
print "Barometric Pressure is : %.2f hPa" %pressure

import smbus

import time

# Get I2C bus

bus = smbus.SMBus(1)

# LPS25HB address, 0x5C(92)

# Select Control register, 0x20(32)

# 0x90(144) Active mode, Continous update

bus.write_byte_data(0x5C, 0x20, 0x90)

time.sleep(0.1)

# LPS25HB address, 0x5C(92)

# Read data back from 0x28(40), with Command register, 0x80(128)

# 3 bytes, Pressure LSB first

data = bus.read_i2c_block_data(0x5C, 0x28 | 0x80, 3)

# Convert the data to hPa

pressure = (data[2] * 65536 + data[1] * 256 + data[0]) / 4096.0

# Output data to screen

print "Barometric Pressure is : %.2f hPa" %pressure

LPS25HB C-Code

#include <stdio.h>
#include <stdlib.h>
#include <linux/i2c-dev.h>
#include <sys/ioctl.h>
#include <fcntl.h>

void main()
{
	// Create I2C bus
	int file;
	char *bus = "/dev/i2c-1";
	if((file = open(bus, O_RDWR)) < 0)
	{
		printf("Failed to open the bus. \n");
		exit(1);
	}
	// Get I2C device, LPS25HB I2C address is 0x5C(72)
	ioctl(file, I2C_SLAVE, 0x5C);
	
	// Select control register(0x20)
	// Active mode, Continuous Update(0x90)
	char config[2] = {0};
	config[0] = 0x20;
	config[1] = 0x90;
	write(file, config, 2); 
	sleep(1);

	// Read 3 bytes of data from register(0x28)
	// Pressure lsb first
	char reg[1] = {0x28 | 0x80};
	write(file, reg, 1);
	char data[3] = {0};
	if(read(file, data, 3) != 3)
	{
		printf("Error : Input/Output error \n");
	}
	else
	{
		// Convert the data
		float pressure = ((data[2] * 65536) + ((data[1] * 256) + data[0])) / 4096.0;

		// Output data to screen
		printf("Pressure is : %.2f hPa \n", pressure);
	}
}

#include <stdio.h>

#include <stdlib.h>

#include <linux/i2c-dev.h>

#include <sys/ioctl.h>

#include <fcntl.h>

void main()

{

// Create I2C bus

int file;

char *bus = "/dev/i2c-1";

if((file = open(bus, O_RDWR)) < 0)

{

printf("Failed to open the bus. \n");

exit(1);

}

// Get I2C device, LPS25HB I2C address is 0x5C(72)

ioctl(file, I2C_SLAVE, 0x5C);

// Select control register(0x20)

// Active mode, Continuous Update(0x90)

char config[2] = {0};

config[0] = 0x20;

config[1] = 0x90;

write(file, config, 2);

sleep(1);

// Read 3 bytes of data from register(0x28)

// Pressure lsb first

char reg[1] = {0x28 | 0x80};

write(file, reg, 1);

char data[3] = {0};

if(read(file, data, 3) != 3)

{

printf("Error : Input/Output error \n");

}

else

{

// Convert the data

float pressure = ((data[2] * 65536) + ((data[1] * 256) + data[0])) / 4096.0;

// Output data to screen

printf("Pressure is : %.2f hPa \n", pressure);

}

LPS25HB CircuitPython Code

CircuitPython Library can be found here

import time
import board
import adafruit_lps2x

i2c = board.I2C()  # uses board.SCL and board.SDA
# i2c = board.STEMMA_I2C()  # For using the built-in STEMMA QT connector on a microcontroller
# uncomment and comment out the line after to use with the LPS22
# lps = adafruit_lps2x.LPS22(i2c)
lps = adafruit_lps2x.LPS25(i2c)

while True:
    print("Pressure: %.2f hPa" % lps.pressure)
    print("Temperature: %.2f C" % lps.temperature)
    time.sleep(1)

import time

import board

import adafruit_lps2x

i2c = board.I2C() # uses board.SCL and board.SDA

# i2c = board.STEMMA_I2C() # For using the built-in STEMMA QT connector on a microcontroller

# uncomment and comment out the line after to use with the LPS22

# lps = adafruit_lps2x.LPS22(i2c)

lps = adafruit_lps2x.LPS25(i2c)

while True:

print("Pressure: %.2f hPa" % lps.pressure)

print("Temperature: %.2f C" % lps.temperature)

time.sleep(1)

PCB Board Milling / Gerber File

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