Receive accurate readings of air pressure with LPS25HB and ATmega644P

Your favorite weather forecaster

Published Jun 21, 2023

Click board™

Barometer Click

Dev. board

EasyAVR v7

Compiler

NECTO Studio

MCU

ATmega644P

With its ability to detect subtle pressure variations, this solution helps you make informed decisions regarding outdoor activities and travel plans

Hardware Overview

How does it work?

Barometer Click is based on the LPS25HB, a high-resolution, digital output pressure sensor from STMicroelectronics. The LPS25HB includes a sensing element based on a piezoresistive Wheatstone bridge approach. When pressure is applied, the membrane deflection induces an imbalance in the Wheatstone bridge piezoresistance, whose output signal is converted into a 24-bit digital value by the selectable digital interface. The LPS25HB's interface is factory-calibrated at three temperatures and two pressures for sensitivity and accuracy. The LPS25HB delivers low-pressure noise with low power consumption and operates over an extended temperature range. It has a selectable

absolute pressure range, from 260 up to 1260hPa, with typical absolute pressure and temperature accuracy of ±0.2hPa and ±2°C, ideally suited for various pressure-based applications. Barometer Click allows the use of both I2C and SPI interfaces with a maximum frequency of 400kHz for I2C and 10MHz for SPI communication. The selection can be made by positioning SMD jumpers in an appropriate position marked as I2C or SPI. 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 LPS25HB allows choosing the least significant bit (LSB) of its I2C slave address using the SMD jumper labeled I2C ADR. This Click board™

also possesses an additional interrupt pin, routed to the INT pin on the mikroBUS™ socket labeled as RDY, indicating when a new measured pressure data is available, simplifying data synchronization in digital systems or optimizing system power consumption. This Click board™ can be operated only with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. However, the Click board™ comes equipped with a library containing functions and an example code that can be used as a reference for further development.

Features overview

Development board

EasyAVR v7 is the seventh generation of AVR development boards specially designed for the needs of rapid development of embedded applications. It supports a wide range of 16-bit AVR microcontrollers from Microchip and has a broad set of unique functions, such as a powerful onboard mikroProg programmer and In-Circuit debugger over USB. The development board is well organized and designed so that the end-user has all the necessary elements in one place, such as switches, buttons, indicators, connectors, and others. With four different connectors for each port, EasyAVR v7 allows you to connect accessory boards, sensors, and custom electronics more

efficiently than ever. Each part of the EasyAVR v7 development board contains the components necessary for the most efficient operation of the same board. An integrated mikroProg, a fast USB 2.0 programmer with mikroICD hardware In-Circuit Debugger, offers many valuable programming/debugging options and seamless integration with the Mikroe software environment. Besides it also includes a clean and regulated power supply block for the development board. It can use a wide range of external power sources, including an external 12V power supply, 7-12V AC or 9-15V DC via DC connector/screw terminals, and a power source via the USB Type-B (USB-B)

connector. Communication options such as USB-UART and RS-232 are also included, alongside the well-established mikroBUS™ standard, three display options (7-segment, graphical, and character-based LCD), and several different DIP sockets which cover a wide range of 16-bit AVR MCUs. EasyAVR v7 is an integral part of the Mikroe ecosystem for rapid development. Natively supported by Mikroe software tools, it covers many aspects of prototyping and development thanks to a considerable number of different Click boards™ (over a thousand boards), the number of which is growing every day.

Microcontroller Overview

MCU Card / MCU

Architecture

AVR

MCU Memory (KB)

Silicon Vendor

Microchip

Pin count

RAM (Bytes)

4096

Used MCU Pins

mikroBUS™ mapper

RST

SPI Chip Select

PA5

SPI Clock

PB7

SCK

SPI Data OUT

PB6

MISO

SPI Data IN

PB5

MOSI

Power Supply

3.3V

Ground

GND

PWM

Data Ready

PD2

INT

I2C Clock

PC0

SCL

I2C Data

PC1

SDA

Ground

GND

Take a closer look

Click board™ Schematic

Step by step

Project assembly

EasyAVR v7 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the EasyAVR v7 as your development board.

NECTO Output Selection Step Image hardware assembly

In the advanced settings, pay special attention to the Redirect standard output field. By default, it is set to Application output as the method of displaying final results. To show results via a UART terminal, select the “UART” option in that field and click the “SAVE” button. You will be returned to the Compiler field, and now you can move on to the next step by pressing the “NEXT” button.

Buck 22 Click front image hardware assembly

EasyAVR v7 MB 1 - upright/background hardware assembly

NECTO Compiler Selection Step Image hardware assembly

Necto DIP image step 7 hardware assembly

EasyPIC PRO v7a Display Selection 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 Barometer Click driver.

Key functions:

barometer_get_temperature_c - Read temperature in degrees Celsius function
barometer_get_pressure - Read pressure in milibars function
barometer_check_status - Check sensor status 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 
 * \brief Barometer Click example
 * 
 * # Description
 * This application measures temperature and pressure data.
 *
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * Initialization driver enable's - I2C, set default configuration and start write log.
 * 
 * ## Application Task  
 * This is a example which demonstrates the use of Barometer Click board.
 * ## NOTE
 * External pull-up resistors are required on I2C lines, if the Click board is configured for I2C mode.
 * 
 * 
 * \author MikroE Team
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "barometer.h"

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

static barometer_t barometer;
static log_t logger;

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

void application_init ( void )
{
    log_cfg_t log_cfg;
    barometer_cfg_t 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( log_cfg );
    log_init( &logger, &log_cfg );
    log_info( &logger, "---- Application Init ----" );

    //  Click initialization.

    barometer_cfg_setup( &cfg );
    BAROMETER_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    barometer_init( &barometer, &cfg );

    barometer_default_cfg( &barometer );

    // Check sensor id
    if ( barometer_check_id( &barometer ) != BAROMETER_DEVICE_ID )
    {
        log_printf( &logger, "   ERROR  \r\n " );
    }
    else
    {
        log_printf( &logger, "   Initialization  \r\n" );
    }
        
    log_printf( &logger, "-------------------------------- \r\n" );
    Delay_100ms( );
}

void application_task ( void )
{
    float temperature_c;
    float pressure;

    temperature_c = barometer_get_temperature_c( &barometer );
    Delay_100ms( );

    pressure = barometer_get_pressure( &barometer );
    Delay_100ms( );

    log_printf( &logger, " Temperature : %.2f\r\n", temperature_c );

    log_printf( &logger, " Pressure    : %.2f\r\n", pressure );
    log_printf( &logger, "-------------------------------- \r\n" );

    Delay_1sec( );
}

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