Beginner
10 min

Detect how much pressure is in the air with LPS331AP and STM32F031K6

Absolute piezoresistive pressure sensor for different environments and applications

Pressure Click with Nucleo 32 with STM32F031K6 MCU

Published Oct 01, 2024

Click board™

Pressure Click

Dev. board

Nucleo 32 with STM32F031K6 MCU

Compiler

NECTO Studio

MCU

STM32F031K6

Measure pressure accurately, with a typical relative accuracy of ±0.1mbar and an absolute accuracy of ±2mbar, even when subjected to high pressures

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Hardware Overview

How does it work?

Pressure Click is based on the LPS331AP, a high accuracy, low-power 24-bit absolute barometric pressure sensor from STMicroelectronics. The LPS331AP provides a typical relative accuracy over pressure of ±0.1mbar and absolute accuracy of ±2mbar with high overpressure capability. It measures absolute pressure from 260mbar to 1260mbar over a wide operating temperature range. The complete device includes a sensing element based on a piezoresistive Wheatstone bridge and an interface that takes the information from the sensing element to the host MCU as a digital signal. The sensing element consists of a suspended membrane realized inside a single mono-silicon substrate capable of detecting

pressure, manufactured using a dedicated process developed by ST called VENSENS. This process allows building of a mono-silicon membrane above an air cavity with a controlled gap and defined pressure. On the other hand, the LPS331AP's interface is manufactured using a standard CMOS process and factory calibrated at three temperatures and two pressures for sensitivity and accuracy. Pressure Click allows using both I2C and SPI interfaces. The selection can be made by positioning SMD jumpers labeled as COMM SEL in an appropriate position. Note that all the jumpers' positions must be on the same side, or the Click board™ may become unresponsive. While the I2C interface is selected, the LPS331AP allows

choosing the least significant bit (LSB) of its I2C slave address using the SMD jumper labeled I2C ADD. This Click board™ also possesses an additional interrupt pin, routed to the INT pin on the mikroBUS™ socket, indicating when a specific pressure event occurs. This Click board™ can only be operated with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. Also, this Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used as a reference for further development.

Pressure Click hardware overview image

Features overview

Development board

Nucleo 32 with STM32F031K6 MCU board provides an affordable and flexible platform for experimenting with STM32 microcontrollers in 32-pin packages. Featuring Arduino™ Nano connectivity, it allows easy expansion with specialized shields, while being mbed-enabled for seamless integration with online resources. The

board includes an on-board ST-LINK/V2-1 debugger/programmer, supporting USB reenumeration with three interfaces: Virtual Com port, mass storage, and debug port. It offers a flexible power supply through either USB VBUS or an external source. Additionally, it includes three LEDs (LD1 for USB communication, LD2 for power,

and LD3 as a user LED) and a reset push button. The STM32 Nucleo-32 board is supported by various Integrated Development Environments (IDEs) such as IAR™, Keil®, and GCC-based IDEs like AC6 SW4STM32, making it a versatile tool for developers.

Nucleo 32 with STM32F031K6 MCU double side image

Microcontroller Overview

MCU Card / MCU

default

Architecture

ARM Cortex-M0

MCU Memory (KB)

32

Silicon Vendor

STMicroelectronics

Pin count

32

RAM (Bytes)

4096

You complete me!

Accessories

Click Shield for Nucleo-32 is the perfect way to expand your development board's functionalities with STM32 Nucleo-32 pinout. The Click Shield for Nucleo-32 provides two mikroBUS™ sockets to add any functionality from our ever-growing range of Click boards™. We are fully stocked with everything, from sensors and WiFi transceivers to motor control and audio amplifiers. The Click Shield for Nucleo-32 is compatible with the STM32 Nucleo-32 board, providing an affordable and flexible way for users to try out new ideas and quickly create prototypes with any STM32 microcontrollers, choosing from the various combinations of performance, power consumption, and features. The STM32 Nucleo-32 boards do not require any separate probe as they integrate the ST-LINK/V2-1 debugger/programmer and come with the STM32 comprehensive software HAL library and various packaged software examples. This development platform provides users with an effortless and common way to combine the STM32 Nucleo-32 footprint compatible board with their favorite Click boards™ in their upcoming projects.

Click Shield for Nucleo-32 accessories 1 image

Used MCU Pins

mikroBUS™ mapper

NC
NC
AN
NC
NC
RST
SPI Chip Select
PA4
CS
SPI Clock
PB3
SCK
SPI Data OUT
PB4
MISO
SPI Data IN
PB5
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
NC
NC
PWM
Interrupt
PA12
INT
NC
NC
TX
NC
NC
RX
I2C Clock
PB6
SCL
I2C Data
PB7
SDA
NC
NC
5V
Ground
GND
GND
1

Take a closer look

Click board™ Schematic

Pressure Click Schematic schematic

Step by step

Project assembly

Click Shield for Nucleo-144 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the Nucleo 32 with STM32F031K6 MCU as your development board.

Click Shield for Nucleo-144 front image hardware assembly
Nucleo 144 with STM32L4A6ZG MCU front image hardware assembly
2x4 RGB Click front image hardware assembly
Prog-cut hardware assembly
Nucleo-32 with STM32 MCU MB 1 - upright/background hardware assembly
Necto image step 2 hardware assembly
Necto image step 3 hardware assembly
Necto image step 4 hardware assembly
Necto image step 5 hardware assembly
Necto image step 6 hardware assembly
Clicker 4 for STM32F4 HA MCU Step hardware assembly
Necto No Display image step 8 hardware assembly
Necto image step 9 hardware assembly
Necto image step 10 hardware assembly
Debug Image Necto Step hardware assembly

Track your results in real time

Application Output

1. Application Output - In Debug mode, the 'Application Output' window enables real-time data monitoring, offering direct insight into execution results. Ensure proper data display by configuring the environment correctly using the provided tutorial.

2. UART Terminal - Use the UART Terminal to monitor data transmission via a USB to UART converter, allowing direct communication between the Click board™ and your development system. Configure the baud rate and other serial settings according to your project's requirements to ensure proper functionality. For step-by-step setup instructions, refer to the provided tutorial.

3. Plot Output - The Plot feature offers a powerful way to visualize real-time sensor data, enabling trend analysis, debugging, and comparison of multiple data points. To set it up correctly, follow the provided tutorial, which includes a step-by-step example of using the Plot feature to display Click board™ readings. To use the Plot feature in your code, use the function: plot(*insert_graph_name*, variable_name);. This is a general format, and it is up to the user to replace 'insert_graph_name' with the actual graph name and 'variable_name' with the parameter to be displayed.

Software Support

Library Description

This library contains API for Pressure Click driver.

Key functions:

  • pressure_generic_single_write - Generic Single Write function

  • pressure_generic_multiple_read - Generic Multiple Read function

  • pressure_get_pressure - Pressure Get function

Open Source

Code example

The complete application code and a ready-to-use project are available through the NECTO Studio Package Manager for direct installation in the NECTO Studio. The application code can also be found on the MIKROE GitHub account.

/*!
 * \file main.c
 * \brief Pressure Click example
 *
 * # Description
 * This is a example which demonstrates the use of Pressure Click board.
 * Measured pressure and temperature data from the LPS331AP sensor on Pressure
 * Click.
 *
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * Initializes I2C/SPI serial interface and puts a device to the initial state.
 * Also initializes UART console module for results logging.
 *
 * ## Application Task
 * Reads the pressure and temperature results in standard units when
 * measurement was done and sends results to the console (usb uart terminal).
 * Repeats operation every 500ms.
 *
 * \author Nemanja Medakovic
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "pressure.h"


// ------------------------------------------------------------------ VARIABLES

static pressure_t pressure;
static log_t console;
static const uint8_t deg_cels[ 3 ] = { 176, 'C', 0 };

// ------------------------------------------------------ APPLICATION FUNCTIONS

void application_init( void )
{
    pressure_cfg_t pressure_cfg;
    log_cfg_t console_cfg;

    /** 
     * Logger initialization.
     * Default baud rate: 115200
     * Default log level: LOG_LEVEL_DEBUG
     * @note If USB_UART_RX and USB_UART_TX 
     * are defined as HAL_PIN_NC, you will 
     * need to define them manually for log to work. 
     * See @b LOG_MAP_USB_UART macro definition for detailed explanation.
     */
    LOG_MAP_USB_UART( console_cfg );
    log_init( &console, &console_cfg );
    log_info( &console, "---- Application Init ----" );

    //  Click initialization.
    pressure_cfg_setup( &pressure_cfg );
    PRESSURE_MAP_MIKROBUS( pressure_cfg, MIKROBUS_1 );
    pressure_init( &pressure, &pressure_cfg );
    pressure_sw_reset( &pressure );
    pressure_default_cfg( &pressure );
}

void application_task( void )
{
    uint8_t status;
    float press;
    float temp;

    status = pressure_get_status( &pressure, PRESSURE_FLAG_MASK_P_DATA_RDY |
                                             PRESSURE_FLAG_MASK_T_DATA_RDY );

    while ( !status )
    {
        status = pressure_get_status( &pressure, PRESSURE_FLAG_MASK_P_DATA_RDY |
                                                 PRESSURE_FLAG_MASK_T_DATA_RDY );
    }

    press = pressure_get_pressure( &pressure );
    temp = pressure_get_temperature( &pressure );

    log_printf( &console, "** Pressure is %.2f mbar\r\n", press );
    log_printf( &console, "** Temperature is %.2f ", temp );
    log_printf( &console, "%s\r\n", deg_cels );
    log_printf( &console, "**************************************\r\n" );

    Delay_ms ( 500 );
}

int main ( void ) 
{
    /* Do not remove this line or clock might not be set correctly. */
    #ifdef PREINIT_SUPPORTED
    preinit();
    #endif
    
    application_init( );
    
    for ( ; ; ) 
    {
        application_task( );
    }

    return 0;
}


// ------------------------------------------------------------------------ END

Additional Support

Resources

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