Intermediate
30 min
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Achieve unparalleled precision in sensing both magnetic and gravitational fields using LSM303AGR and STM32F415ZG

Your window into magnetic and gravitational fields

LSM303AGR Click with UNI-DS v8

Published Sep 13, 2023

Click board™

LSM303AGR Click

Development board

UNI-DS v8

Compiler

NECTO Studio

MCU

STM32F415ZG

Our innovative solution opens the door to a new era of sensing capabilities, allowing you to precisely measure the magnetic and gravitational fields along three orthogonal axes. It's your key to unlocking groundbreaking insights in geophysics, navigation, and beyond.

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Hardware Overview

How does it work?

LSM303AGR Click is based on the LSM303AGR, a low-power and high-performance sensor featuring a digital linear acceleration sensor, and a digital magnetic sensor from STMicroelectronics, capable of sensing magnetic and gravitational fields in all three axes. The sensor is a highly integrated system in package (SIP), offering two independent sensors, charge amplifiers, A/D converters, and control logic sections. There are two independent I2C slave addresses for each of the sensors: 0011001b is the slave address of the accelerometer, while the 0011110b is the slave address of the magnetic sensor. These are 7bit addresses, to complete the address sequence, an R/W bit needs to be added at the end. An interrupt pin (INT_MAG/DRDY) allows the interrupt generated by an event within the LSM303AGR IC, to alert the host MCU. This pin is routed to the mikroBUS™ INT pin. The power of the LSM303AGR IC lies in its configurable interrupt engine. The function, threshold, and timing of the interrupt signal on the INT pin can be completely defined by the user. Its behavior can be programmed by setting a range of appropriate registers via the I2C bus. The sensor offers detection of many events, caused either by the sensors themselves or by the error/status events within the sensor IC. For example, the interrupt can be generated if there is data ready to be transferred to the host MCU if the FIFO buffer overflow occurred and so on.

A combination of events is also available, with either 'OR' or 'AND' function between the generated events. It allows developing HID applications, which react on tapping, moving, positioning, etc. The LSM303AGR device offers digital filtering, compensation, self-test, and more. It allows resolution, sampling time and power consumption to be adjusted, allowing the Click board™ to be tailored to any application. Trimming values for zero-g level, zero-gauss level, and sensitivity adjustment are stored into the internal non-volatile memory and are copied to the registers upon restart. This allows the sensor to perform accurate measurements without repeated calibration after each power-up cycle. Another feature used to increase the accuracy of the sensor is the hard-iron compensation, which compensates the readings, in cases when an object with magnetic properties is placed near the sensor, permanently biasing the output values. Six registers hold magnetic values for the compensation and are automatically subtracted from readings. Many signal processing features such as the low-pass and high-pass filtering, also help to obtain accurate and reliable readings from this sensor. A self-test procedure can be used to verify the functionality of the device. The internal current generates an internal magnetic field, which is then sensed by the sensors. The readings during self-test should look like in the table,

given in the LSM303AGR datasheet. If these readings look differently, a particular device can be discarded. The device contains a FIFO buffer, which can be used for the accelerometer sensor only. It is 32 levels deep, allowing 32 sets of readings along X, Y, and Z axes to be stored. The buffer can be bypassed, it can be fixed so that new data is discarded when it is full, and it can be set to streaming mode so that the new data pushes out the oldest information from the buffer. An interrupt can be triggered if a programmed threshold is exceeded so that the buffer can be read before the data is lost. The sampling frequency and the resolution can be selected from 1Hz up to 5.736 kHz and from 8 bits up to 12 bits. These settings affect the power consumption. The device can work in normal mode, high-resolution mode, and low power mode. This affects the acquisition time as well as the power consumption. In addition, the device can work in continuous mode, or in a single shot mode. A single shot mode allows the device to consume less power, as the single measurement is done on a command, after which device reverts to idle mode and the DRDY (data ready) bit is set. Again, the datasheet of the LSM303AGR offers an in-depth explanation of all the registers and their functionality.

LSM303AGR Click top side image
LSM303AGR 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

default

Type

8th Generation

Architecture

ARM Cortex-M4

MCU Memory (KB)

1024

Silicon Vendor

STMicroelectronics

Pin count

144

RAM (Bytes)

196608

Used MCU Pins

mikroBUS™ mapper

NC
NC
AN
NC
NC
RST
NC
NC
CS
NC
NC
SCK
NC
NC
MISO
NC
NC
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
NC
NC
PWM
Interrupt
PD3
INT
NC
NC
TX
NC
NC
RX
I2C Clock
PB8
SCL
I2C Data
PB9
SDA
NC
NC
5V
Ground
GND
GND
1

Take a closer look

Schematic

LSM303AGR 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
Buck 22 Click front image hardware assembly
SiBRAIN for PIC32MZ1024EFK144 front image hardware assembly
v8 SiBRAIN 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 LSM303AGR Click driver.

Key functions:

  • lsm303agr_get_acc_axis_x - Reading the raw X axis data and calculating the value

  • lsm303agr_get_mag_axis_x - Reading the raw X axis data and calculating the value

  • lsm303agr_get_mag_axis_y - Reading the raw Y axis data and calculating the value

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 LSM303AGR Click example
 * 
 * # Description
 * This example returns accel and magnet values from the LSM303AGR sensor.
 *
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * I2C Driver initaliation and setting operating modes of accelerometer and
 * magnetometer 
 * 
 * ## Application Task  
 * Reading accelerometer and magnetometer axis X,Y,Z and displaying via UART
 * 
 * 
 * \author MikroE Team
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "lsm303agr.h"

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

static lsm303agr_t lsm303agr;
static log_t logger;
static float read_data;

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

void application_init ( void )
{
    log_cfg_t log_cfg;
    lsm303agr_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.

    lsm303agr_cfg_setup( &cfg );
    LSM303AGR_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    lsm303agr_init( &lsm303agr, &cfg );
    
    lsm303agr_default_cfg ( &lsm303agr );
   
}

void application_task ( void )
{
    //  Task implementation.

    log_printf(&logger, "======== Accelerometer data ========\r\n");
    
    read_data = lsm303agr_get_acc_axis_x ( &lsm303agr );
    log_printf(&logger, "X Axis : %.2f\r\n", read_data);

    read_data = lsm303agr_get_acc_axis_y ( &lsm303agr );
    log_printf(&logger, "Y Axis : %.2f\r\n", read_data);

    read_data = lsm303agr_get_acc_axis_z ( &lsm303agr );
    log_printf(&logger, "Z Axis : %.2f\r\n", read_data);
    
    log_printf(&logger, "======== Mangetometer data ========\r\n");
    
    read_data = lsm303agr_get_mag_axis_x ( &lsm303agr );
    log_printf(&logger, "X Axis : %.2f\r\n", read_data);

    read_data = lsm303agr_get_mag_axis_y ( &lsm303agr );
    log_printf(&logger, "Y Axis : %.2f\r\n", read_data);

    read_data = lsm303agr_get_mag_axis_z ( &lsm303agr );
    log_printf(&logger, "Z Axis : %.2f\r\n", read_data);

    Delay_ms( 2000 );
}

void main ( void )
{
    application_init( );

    for ( ; ; )
    {
        application_task( );
    }
}


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

Additional Support

Resources