Balance barometric pressure with BMP280 and STM32F405RG
Under pressure, we thrive!
Published Oct 12, 2023
Click board™
Pressure 4 Click
Dev Board
UNI-DS v8
Compiler
NECTO Studio
MCU
STM32F405RG
Trust in our digital barometric sensor to keep you informed, whether you're an outdoor enthusiast, researcher, or IoT developer, enabling data-driven decisions and insights
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Hardware Overview
How does it work?
Pressure 4 Click is based on the BMP280, a digital pressure sensor from Bosch Sensortec. This sensor is produced using the Bosch proprietary APSM manufacturing technology. APSM is an abbreviation for the Advanced Porous Silicon Membrane, which is CMOS compatible technology, used to hermetically seal the sensor cavity, in an all-silicon process. This advanced MEMS technology offers a high measurement precision of only 0.12 hPa, as well as low TOC (thermal coefficient) of only 1.5 Pa/K. The sensor is enclosed in a small metal lid housing and is very resilient: it can operate in a range of 300 hPa to 1100 hPa but can withstand up to 20,000 hPa before the membrane breaks down. The BMP280 offers a set of pressure and temperature measurement options. It can be programmed to skip either thermal or pressure measurement, allowing faster measurement of the required property. The low TOC of only 1.5K/Pa allows reading of the pressure with very small drift over temperature. Resolution of 0.12 hPa allows calculating of the altitude with the accuracy of 1m, which is ideal for indoor navigation applications (drones, flying toy models, and similar). Since this device is aimed at low power applications, it is
powered by the mikroBUS™ 3.3V rail and does not allow voltages up to 5V. Therefore the Click board™ supports only 3.3V MCUs and it is not intended to be connected or controlled via the 5V MCU without a proper level shifting circuitry. This sensor is comprised of a mixed signal front end (ASIC) and the piezo-sensitive pressure sensing element. The ASIC section provides analog to digital conversion of the measurement as well as the signal processing, in the form of the IIR filtering. The measurement readings and the compensation parameters are available at I2C or SPI bus pins of the BMP280 routed to the mikroBUS™ standard SPI and I2C pins. Pressure 4 click offers a selection between the two, by switching SMD jumpers labeled as I2C SPI to an appropriate position. Note that all the jumpers have to be placed to the same side, as mixed SPI and I2C positions will render the Click board™ unresponsive. Additionally, selection of the I2C communication protocol allows the least significant bit (LSB) of the I2C slave address of the device to be set. This can be done with the SMD jumper, labeled as I2C ADDR. The overall power consumption depends on several factors, such as the oversampling value, measurement rate, power
mode, standby duration, and so on. Bosch Sensortec recommends a set of operational parameters for different applications, in a form of a table, in the BMP280 datasheet. In general, this sensor allows several power modes, regardless of the selected measurement parameters, such as Sleep, Forced, and Normal mode. When the measurement is completed, the raw ADC values will be available in the output registers. However, to obtain actual pressure and temperature readings, a compensation algorithm needs to be applied to these raw values. A set of compensation parameters is available in the non-volatile memory of each sensor device. These compensation parameters take into account slight differences between the produced sensors and each BMP280 sensor device has its own set of compensation parameters. The BMP280 datasheet offers detailed instructions on how to apply these compensating algorithms properly. However, MikroElektronika provides a library that contains functions, which can be used for the simplified operation of the Pressure 4 click. The library also contains an example application, which demonstrates their use. This example application can be used as a reference for custom designs.
Features overview
Development board
UNI-DS v8 is a development board specially designed for the needs of rapid development of embedded applications. It supports a wide range of microcontrollers, such as different STM32, Kinetis, TIVA, CEC, MSP, PIC, dsPIC, PIC32, and AVR MCUs regardless of their number of pins, and a broad set of unique functions, such as the first-ever embedded debugger/programmer over WiFi. The development board is well organized and designed so that the end-user has all the necessary elements, such as switches, buttons, indicators, connectors, and others, in one place. Thanks to innovative manufacturing technology, UNI-DS v8 provides a fluid and immersive working experience, allowing access anywhere and under any
circumstances at any time. Each part of the UNI-DS v8 development board contains the components necessary for the most efficient operation of the same board. An advanced integrated CODEGRIP programmer/debugger module offers many valuable programming/debugging options, including support for JTAG, SWD, and SWO Trace (Single Wire Output)), and seamless integration with the Mikroe software environment. Besides, it also includes a clean and regulated power supply module for the development board. It can use a wide range of external power sources, including a battery, an external 12V power supply, and a power source via the USB Type-C (USB-C) connector. Communication options such as USB-UART, USB
HOST/DEVICE, CAN (on the MCU card, if supported), and Ethernet is also included. In addition, it also has the well-established mikroBUS™ standard, a standardized socket for the MCU card (SiBRAIN standard), and two display options for the TFT board line of products and character-based LCD. UNI-DS v8 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
Type
8th Generation
Architecture
ARM Cortex-M4
MCU Memory (KB)
1024
Silicon Vendor
STMicroelectronics
Pin count
64
RAM (Bytes)
196608
Used MCU Pins
mikroBUS™ mapper
Take a closer look
Schematic
Step by step
Project assembly
Start by selecting your development board and Click board™. Begin with the UNI-DS v8 as your development board.
Track your results in real time
Application Output
After pressing the "FLASH" button on the left-side panel, it is necessary to open the UART terminal to display the achieved results. By clicking on the Tools icon in the right-hand panel, multiple different functions are displayed, among which is the UART Terminal. Click on the offered "UART Terminal" icon.
Once the UART terminal is opened, the window takes on a new form. At the top of the tab are two buttons, one for adjusting the parameters of the UART terminal and the other for connecting the UART terminal. The tab's lower part is reserved for displaying the achieved results. Before connecting, the terminal has a Disconnected status, indicating that the terminal is not yet active. Before connecting, it is necessary to check the set parameters of the UART terminal. Click on the "OPTIONS" button.
In the newly opened UART Terminal Options field, we check if the terminal settings are correct, such as the set port and the Baud rate of UART communication. If the data is not displayed properly, it is possible that the Baud rate value is not set correctly and needs to be adjusted to 115200. If all the parameters are set correctly, click on "CONFIGURE".
The next step is to click on the "CONNECT" button, after which the terminal status changes from Disconnected to Connected in green, and the data is displayed in the Received data field.
Software Support
Library Description
This library contains API for Pressure 4 Click driver.
Key functions:
pressure4_read_id- This function returns the contents of the chipid registerpressure4_get_temperature- This function returning the calculated temperature valuepressure4_get_pressure- This function returning the calculated value of the pressure
Open Source
Code example
This example can be found in NECTO Studio. Feel free to download the code, or you can copy the code below.
/*!
* \file
* \brief Pressure4 Click example
*
* # Description
* This app measure barometric pressure.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Initializes the click board.
*
* ## Application Task
* The pressure and temperature data is read from the sensor
* and it is printed to the UART.
*
* \author MikroE Team
*
*/
// ------------------------------------------------------------------- INCLUDES
#include "board.h"
#include "log.h"
#include "pressure4.h"
// ------------------------------------------------------------------ VARIABLES
static pressure4_t pressure4;
static log_t logger;
// ------------------------------------------------------ APPLICATION FUNCTIONS
void application_init ( void )
{
log_cfg_t log_cfg;
pressure4_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.
pressure4_cfg_setup( &cfg );
PRESSURE4_MAP_MIKROBUS( cfg, MIKROBUS_1 );
pressure4_init( &pressure4, &cfg );
pressure4_default_cfg( &pressure4 );
Delay_ms( 100 );
}
void application_task ( void )
{
double pressure;
double temperature;
temperature = pressure4_get_temperature( &pressure4 );
log_printf( &logger, "Temperature : %.2lf \r\n", temperature );
Delay_ms( 100 );
pressure = pressure4_get_pressure( &pressure4 );
log_printf( &logger, "Pressure : %.2lf hPa \r\n", pressure );
log_printf( &logger, "========================\r\n" );
Delay_ms( 500 );
}
void main ( void )
{
application_init( );
for ( ; ; )
{
application_task( );
}
}
// ------------------------------------------------------------------------ END
