30 min

Monitor and control pressure differentials with ease using LMIS025B and STM32F207ZG

Digital excellence in pressure sensing

VAV Press Click with UNI-DS v8

Published Oct 14, 2023

Click board™

VAV Press Click

Development board



NECTO Studio



Our digital differential pressure sensor is engineered to provide precise and reliable readings for a wide range of applications, from industrial automation to environmental monitoring



Hardware Overview

How does it work?

VAV Press Click is based on the LMIS025B, a low differential pressure sensor from TE Connectivity that offers a digital output for reading pressure over the specified pressure span. The innovative LMI technology features superior sensitivity, especially for ultra-low pressures ranging from 0 to 25Pa / 0 to 0.25mbar (0.1 in H2O). It is based on thermal flow measurement of gas through a micro-flow channel integrated within the sensor chip. The extremely low gas flow through the sensor ensures high immunity to dust contamination, humidity, and long tubing compared to other flow-based pressure sensors,

including the outstanding long-term stability, precision with patented real-time offset compensation, and linearization techniques. The LMIS025B offers two modes of operation: Continuous mode with a 5ms sampling time, which provides a near-continuous stream of pressure data, and low-power mode with a 400μA Standby current which wakes the device from Sleep to serve pressure data “on-demand”. The first measurement in either mode is available after a warm-up and conversion sequence, which takes approximately 25 ms. VAV Press Click communicates with MCU using the standard I2C

2-Wire interface, offering linearized digital output through a 16-bit sigma-delta A/D conversion. Besides, it also allows the choice of the least significant bit of its I2C slave address by positioning the SMD jumper labeled as ADDR SEL to an appropriate position marked as 0 and 1. 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. Also, it comes equipped with a library containing functions and an example code that can be used as a reference for further development.

VAV Press Click top side image
VAV Press Click bottom side image

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.

UNI-DS v8 horizontal image

Microcontroller Overview

MCU Card / MCU



8th Generation


ARM Cortex-M3

MCU Memory (KB)


Silicon Vendor


Pin count


RAM (Bytes)


Used MCU Pins

mikroBUS™ mapper

Power Supply
I2C Clock
I2C Data

Take a closer look


VAV Press Click Schematic schematic

Step by step

Project assembly

Fusion for PIC v8 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the UNI-DS v8 as your development board.

Fusion for PIC v8 front image hardware assembly
GNSS2 Click front image hardware assembly
SiBRAIN for PIC32MZ1024EFK144 front image hardware assembly
GNSS2 Click complete accessories setup image hardware assembly
v8 SiBRAIN Access 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 Compiler Selection Step Image hardware assembly
NECTO Output Selection Step Image hardware assembly
Necto image step 6 hardware assembly
Necto image step 7 hardware assembly
Necto image step 8 hardware assembly
Necto image step 9 hardware assembly
Necto image step 10 hardware assembly
Necto PreFlash Image hardware assembly

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.

UART Application Output Step 1

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.

UART Application Output Step 2

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".

UART Application Output Step 3

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.

UART Application Output Step 4

Software Support

Library Description

This library contains API for VAV Press Click driver.

Key functions:

  • vavpress_set_default_sensor_param - VAV Press set default sensor parameter function

  • vavpress_get_dif_press_and_temp - VAV Press get differential pressure and temperature function

  • vavpress_retrieve_electronic_signature - VAV Press retrieve electronic signature function

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 main.c
 * @brief VavPress Click example
 * # Description
 * This library contains API for the Vav Press click driver.
 * This demo application shows an example of 
 * differential pressure and temperature measurement.
 * The demo application is composed of two sections :
 * ## Application Init
 * Initialization of I2C module and log UART.
 * After driver initialization and default settings, 
 * the app display retrieve the electronic signature 
 * and set the sensor parameters data.
 * ## Application Task
 * This is an example that shows the use of a Vav Press click board™.
 * Logs pressure difference value [ Pa ] and temperature [ degree Celsius ] value.
 * Results are being sent to the Usart Terminal where you can track their changes.
 * @author Nenad Filipovic

#include "board.h"
#include "log.h"
#include "vavpress.h"

static vavpress_t vavpress;
static log_t logger;
static float diff_press;
static float temperature;
vavpress_el_signature_data_t el_signature_data;
vavpress_sensor_param_data_t param_data;

void application_init ( void ) {
    log_cfg_t log_cfg;            /**< Logger config object. */
    vavpress_cfg_t vavpress_cfg;  /**< Click config object. */

     * 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_printf( &logger, "\r\n" );
    log_info( &logger, " Application Init " );

    // Click initialization.

    vavpress_cfg_setup( &vavpress_cfg );
    VAVPRESS_MAP_MIKROBUS( vavpress_cfg, MIKROBUS_1 );
    err_t init_flag = vavpress_init( &vavpress, &vavpress_cfg );
    if ( init_flag == I2C_MASTER_ERROR ) {
        log_error( &logger, " Application Init Error. " );
        log_info( &logger, " Please, run program again... " );

        for ( ; ; );

    vavpress_default_cfg ( &vavpress );
    log_info( &logger, " Application Task " );
    Delay_ms( 100 );
    vavpress_retrieve_electronic_signature( &vavpress, &el_signature_data );
    Delay_ms( 100 );

    log_printf( &logger, "--------------------------------\r\n" );
    log_printf( &logger, " Firmware Version : %.3f        \r\n", el_signature_data.firmware_version );
    log_printf( &logger, " Pressure Range   : %d Pa       \r\n", el_signature_data.pressure_range );
    log_printf( &logger, " Part #           : %.11s       \r\n", el_signature_data.part_number );
    log_printf( &logger, " Lot #            : %.7s        \r\n", el_signature_data.lot_number );
    log_printf( &logger, " Output Type      : %c          \r\n", el_signature_data.output_type );
    log_printf( &logger, " Scale Factor     : %d          \r\n", el_signature_data.scale_factor );
    log_printf( &logger, " Calibration ID   : %.2s        \r\n", el_signature_data.calibration_id );
    log_printf( &logger, " Week number      : %d          \r\n", el_signature_data.week_number );
    log_printf( &logger, " Year number      : %d          \r\n", el_signature_data.year_number );
    log_printf( &logger, " Sequence number  : %d          \r\n", el_signature_data.sequence_number );
    log_printf( &logger, "--------------------------------\r\n" );
    Delay_ms( 2000 );
    param_data.scale_factor_temp = 72;
    param_data.scale_factor_press = el_signature_data.scale_factor;
    param_data.readout_at_known_temperature = 50;
    param_data.known_temperature_c = 24.0;
    Delay_ms( 100 );

void application_task ( void ) {   
    err_t error_flag = vavpress_get_dif_press_and_temp( &vavpress, &param_data, &diff_press, &temperature );
    if ( error_flag == VAVPRESS_OK ) {
        log_printf( &logger, " Diff. Pressure    : %.4f Pa\r\n", diff_press );
        log_printf( &logger, " Temperature       : %.4f C\r\n", temperature );
        log_printf( &logger, "--------------------------------\r\n" );
        Delay_ms( 2000 );
    } else {
        log_error( &logger, " Communcation Error. " );
        log_info( &logger, " Please, run program again... " );

        for ( ; ; );

void main ( void ) {
    application_init( );

    for ( ; ; ) {
        application_task( );

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

Additional Support