Intermediate
30 min

Capture magnetic field data with exceptional detail using AS5311 and PIC18LF24K50

Your guide to accurate magnetometry

Magneto 4 Click with EasyPIC v8

Published Nov 01, 2023

Click board™

Magneto 4 Click

Development board

EasyPIC v8

Compiler

NECTO Studio

MCU

PIC18LF24K50

Discover how our magnetometer solution empowers industries and scientists to navigate the complex world of magnetism with unparalleled accuracy

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Hardware Overview

How does it work?

Magneto 4 Click is based on the AS5311, a high resolution magnetic linear encoder from ams OSRAM which integrates Hall elements, a low-noise analog front-end, and a digital signal processing (DSP), on the same die. It is a System-on-Chip used for performing highly accurate measurements. It is designed to be used along with a multi-pole magnetic strip or ring. A pole length should be 1.0mm, while the strip should be placed about 3mm above the IC surface. The magnetic strip movement is translated into a 12-bit word on the output. In other words, the output is cycled from 0 to 4095 for each 2mm the strip moves. Also, this means that the movement resolution goes down to 488nm per LSB. The AS5311 can output the movement data in several different formats: it can either output the bit-string over the serial interface, or by using the 12-bit pulse-width modulated signal (PWM). The pulse width of the PWM signal starts with 1µs and is increased for every 0.488μm. The maximum pulse width is 4095µs, which corresponds to a magnet movement of 2mm. The incremental outputs allow this Click board™ to be used in place of a mechanical or optical quadrature encoder. These two outputs are phase-shifted for 90 degrees: the output A leads output B when the magnet is moving from right to left and vice-versa:

output B leads output A when the magnet is moving from left to right. The resolution of the incremental outputs is 10 bits per pole pair (1024 steps), which results in a step length of 1.95μm. An additional index pin is triggered for each pulse pair. These pins can be disabled by using the Chip Select (CS) pin: whenever the CS pin is at a HIGH logic level, all the incremental output pins (A, B, Index) are disabled (fixed at a HIGH logic state). To prevent flickering in border-conditions, there is a hysteresis of 2 LSBs implemented. The serial interface is very similar to SPI. However, depending on the correlation between the Chip Select pin and the clock signal logic state, two data modes are available: if the CS pin is pulled to a HIGH logic state (or floating) during the clock HIGH pulse, the AS5311 will report the magnitude (strength) of the magnetic field. Else, it will output the absolute linear position data. The output data contains both the magnetic/positional data bits (11 bits) and status bits (5 bits). The status report includes offset compensation status, "CORDIC" overflow status, linearity alarm status, and two magnetic field strength status bits. The AS5311 can use either two hardware pins (MagINCn, MagENCn) routed to the additional header, or two status bits within the status report. These two bits/pins are used to describe the magnitude of

the magnetic field. The datasheet refers to three different magnetic field magnitudes: green, yellow, and red. The green status represents the optimal strength of the magnetic field. The yellow status indicated that the obtained data may not be accurate, while the red status indicates that the magnetic field generated by the multi-pole strip or ring is weak and it is not recommended to use it. For proper operation of the Click board™, a multi-pole magnetic strip should be properly placed above the IC so that it can move along x-axis only. To support correct placing, the Click board™ comes with four holes, which can be used to accurately position the strip in place. Please refer to the datasheet for more details about the magnetic strip positioning. The Click board™ can work with MCUs that use with both 3.3V and 5V supply voltages. The power supply selection on this click is a bit specific: to select 3.3V, both SMD jumpers grouped under the 3.3V label should be populated, while the SMD jumper under the 5V label should not be populated. Selecting 5V is done by removing two SMD jumpers under the 3.3V label and populating one SMD jumper under the 5V label. Please note that populating all the SMD jumpers at once may lead to malfunction.

Magneto 4 Click hardware overview image

Features overview

Development board

EasyPIC v8 is a development board specially designed for the needs of rapid development of embedded applications. It supports many high pin count 8-bit PIC microcontrollers from Microchip, regardless of their number of pins, and a broad set of unique functions, such as the first-ever embedded debugger/programmer. 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, EasyPIC v8 provides a fluid and immersive working experience, allowing access anywhere and under any

circumstances at any time. Each part of the EasyPIC v8 development board contains the components necessary for the most efficient operation of the same board. In addition to the advanced integrated CODEGRIP programmer/debugger module, which offers many valuable programming/debugging options and seamless integration with the Mikroe software environment, the board 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 DEVICE, and CAN are also included, including the well-established mikroBUS™ standard, two display options (graphical and character-based LCD), and several different DIP sockets. These sockets cover a wide range of 8-bit PIC MCUs, from the smallest PIC MCU devices with only eight up to forty pins. EasyPIC 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.

EasyPIC v8 horizontal image

Microcontroller Overview

MCU Card / MCU

default

Architecture

PIC

MCU Memory (KB)

16

Silicon Vendor

Microchip

Pin count

28

RAM (Bytes)

2048

You complete me!

Accessories

Rotary Magnetic Holder is an addition designed for use alongside a magnetic rotary position sensor. It comes with a plastic stand measuring 22x16x10 millimeters (L x W x H), as well as an adjustable shaft with a 6mm diameter magnet. The plastic frame has four round feet that fit into holes in the board near the magnetic rotary position sensor, with a 6mm diameter hole on top to match the adjustable shaft that carries the magnet. This shaft has a height adjustment screw on it, allowing the user to adjust it between 18 and 22 millimeters. This way, fast prototyping and quick measurements of the magnet characteristics are allowed during development.

Magneto 4 Click accessories image

Used MCU Pins

mikroBUS™ mapper

Encoder Output A
RA3
AN
Encoder Output B
RA0
RST
SPI Chip Select
RA5
CS
SPI Clock
RC3
SCK
SPI Data OUT
RC4
MISO
NC
NC
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
PWM Output
RC1
PWM
Index Output
RB1
INT
NC
NC
TX
NC
NC
RX
NC
NC
SCL
NC
NC
SDA
Power Supply
5V
5V
Ground
GND
GND
2

Take a closer look

Schematic

Magneto 4 Click Schematic schematic

Step by step

Project assembly

EasyPIC v8 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the EasyPIC v8 as your development board.

EasyPIC v8 front image hardware assembly
LTE IoT 5 Click front image hardware assembly
MCU DIP 28 hardware assembly
LTE IoT 5 Click complete accessories setup image hardware assembly
EasyPIC v8 28pin-DIP Access - 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 DIP 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 Magneto 4 Click driver.

Key functions:

  • magneto4_get_magnetic_status - Get Magnetic measurement status

  • magneto4_get_encoder_position - Encoder position

  • magneto4_get_encoder_direction - Encoder direction

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 Magneto4 Click example
 * 
 * # Description
 * Reads and logs magnetic field strength values
 * if magnetic field strength values bigger than 3000, 
 * start magnetic linear position mode,   
 * when moving the sensor from left to right the position for 1 step is reduced.
 *
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * Initializes Driver init and sets start encoder position on the zero.
 * Reads and logs magnetic field strength values.
 * For starting an encoder, it is necessary that the magnetic field strength 
 * is greater than 3000.
 * 
 * ## Application Task  
 * When moving the sensor from left to right, one step is added 
 * and when moving from right to left, the position for 1 step is reduced.
 * 
 * \author Luka Filipovic
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "magneto4.h"

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

static magneto4_t magneto4;
static log_t logger;

static int32_t enc_position;
static int32_t old_position = 255;
static int16_t magnetic_field = 0;

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

void application_init ( void )
{
    log_cfg_t log_cfg;
    magneto4_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.

    magneto4_cfg_setup( &cfg );
    MAGNETO4_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    magneto4_init( &magneto4, &cfg );
    
    magneto4_default_cfg ( &magneto4 );
    
    log_printf( &logger, " --- Please, bring the magnet close ---\r\n" );

    while ( magnetic_field < MAGNETO4_MAX_MAGNETIC_FIELD_VALUE )
    {
        magnetic_field = magneto4_get_magnetic_field( &magneto4 );
        log_printf( &logger, " Magnetic field strength : %d\r\n", magnetic_field );
        Delay_ms( 1000 );
    }
    
    Delay_ms( 1500 );
    log_printf( &logger, " --- Magnetic Linear Position ---\r\n" );
}

void application_task ( void )
{
    //  Task implementation.
    
    magneto4_get_encoder_position( &magneto4 );
    
    enc_position = magneto4.encoder_position;

    if ( old_position != enc_position )
    {
        log_printf( &logger, " Encoder position : %d\r\n", enc_position );
        log_printf( &logger, " ------------------------\r\n" );
    }
    
    old_position = enc_position;
}

void main ( void )
{
    application_init( );

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


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

Additional Support

Resources