Intermediate
30 min

Provide galvanic isolation of digital I2C signals with MAX14937 and MK64FN1M0VDC12

Full i2C interface isolation

I2C Isolator 4 Click with Clicker 2 for Kinetis

Published Mar 02, 2023

Click board™

I2C Isolator 4 Click

Dev Board

Clicker 2 for Kinetis

Compiler

NECTO Studio

MCU

MK64FN1M0VDC12

Completely isolated I2C interface

A

A

Hardware Overview

How does it work?

I2C Isolator 4 Click is based on the MAX14937, a two-channel, 5kVRMS I2C digital isolator from Analog Devices. The MAX14937 bidirectionally buffers the two I2C signals across the isolation barrier and supports I2C clock-stretching while providing 5kVrms of galvanic isolation. It transfers digital signals between circuits with different power domains at ambient temperatures and offers glitch-free operation, excellent reliability,

and very long operational life. The wide temperature range and high isolation voltage make the device ideal for harsh industrial environments. This Click board™ also possesses two terminals labeled as VIN and SDA/SCL at the bottom of the Click board™, where VIN represents the B-side power supply of the isolator, while the other corresponds to the isolated bidirectional logic-bus terminal.

This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the VCC SEL jumper. This way, both 3.3V and 5V capable MCUs can use the communication lines properly. However, the Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used, as a reference, for further development.

i2c-isolator-4-click-hardware-overview

Features overview

Development board

Clicker 2 for Kinetis is a compact starter development board that brings the flexibility of add-on Click boards™ to your favorite microcontroller, making it a perfect starter kit for implementing your ideas. It comes with an onboard 32-bit ARM Cortex-M4F microcontroller, the MK64FN1M0VDC12 from NXP Semiconductors, two mikroBUS™ sockets for Click board™ connectivity, a USB connector, LED indicators, buttons, a JTAG programmer connector, and two 26-pin headers for interfacing with external electronics. Its compact design with clear and easily recognizable silkscreen markings allows you to build gadgets with unique functionalities and

features quickly. Each part of the Clicker 2 for Kinetis development kit contains the components necessary for the most efficient operation of the same board. In addition to the possibility of choosing the Clicker 2 for Kinetis programming method, using a USB HID mikroBootloader or an external mikroProg connector for Kinetis programmer, the Clicker 2 board also includes a clean and regulated power supply module for the development kit. It provides two ways of board-powering; through the USB Micro-B cable, where onboard voltage regulators provide the appropriate voltage levels to each component on the board, or

using a Li-Polymer battery via an onboard battery connector. All communication methods that mikroBUS™ itself supports are on this board, including the well-established mikroBUS™ socket, reset button, and several user-configurable buttons and LED indicators. Clicker 2 for Kinetis is an integral part of the Mikroe ecosystem, allowing you to create a new application in minutes. Natively supported by Mikroe software tools, it covers many aspects of prototyping thanks to a considerable number of different Click boards™ (over a thousand boards), the number of which is growing every day.

Clicker 2 for Kinetis dimensions image

Microcontroller Overview

MCU Card / MCU

default

Architecture

ARM Cortex-M4

MCU Memory (KB)

1024

Silicon Vendor

NXP

Pin count

121

RAM (Bytes)

262144

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
NC
NC
INT
NC
NC
TX
NC
NC
RX
I2C Clock
PD8
SCL
I2C Data
PD9
SDA
Power Supply
5V
5V
Ground
GND
GND
1

Take a closer look

Schematic

I2C Isolator 4 Click Schematic schematic

Step by step

Project assembly

Clicker 2 for PIC32MZ front image hardware assembly

Start by selecting your development board and Click board™. Begin with the Clicker 2 for Kinetis as your development board.

Clicker 2 for PIC32MZ front image hardware assembly
GNSS2 Click front image hardware assembly
Prog-cut hardware assembly
GNSS2 Click complete accessories setup image hardware assembly
Micro B Connector Clicker 2 Access - upright/background hardware assembly
Necto image step 2 hardware assembly
Necto image step 3 hardware assembly
Necto image step 4 hardware assembly
Necto image step 5 hardware assembly
Necto image step 6 hardware assembly
Flip&Click PIC32MZ MCU step hardware assembly
Necto No Display image step 8 hardware assembly
Necto image step 9 hardware assembly
Necto image step 10 hardware assembly
Debug Image Necto Step hardware assembly

Track your results in real time

Application Output via Debug Mode

1. Once the code example is loaded, pressing the "DEBUG" button initiates the build process, programs it on the created setup, and enters Debug mode.

2. After the programming is completed, a header with buttons for various actions within the IDE becomes visible. Clicking the green "PLAY" button starts reading the results achieved with the Click board™. The achieved results are displayed in the Application Output tab.

DEBUG_Application_Output

Software Support

Library Description

This library contains API for I2C Isolator 4 Click driver.

Key functions:

  • i2cisolator4_generic_write I2C Isolator 4 I2C writing function.

  • i2cisolator4_generic_read I2C Isolator 4 I2C reading function.

  • i2cisolator4_set_slave_address I2C Isolator 4 set I2C Slave address 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 I2cIsolator4 Click example
 *
 * # Description
 * This library contains API for the I2C Isolator 4 click driver.
 * This demo application shows an example of an I2C Isolator 4 click 
 * wired to the VAV Press click for reading 
 * 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 set VAV Press click I2C slave address ( 0x5C ) 
 * and enable device.
 *
 * ## Application Task
 * This is an example that shows the use of an I2C Isolator 4 click board™.
 * Logs pressure difference [ Pa ] and temperature [ degree Celsius ] values 
 * of the VAV Press click wired to the I2C Isolator 4 click board™.  
 * Results are being sent to the Usart Terminal where you can track their changes.
 *
 * @note
 * void get_dif_press_and_temp ( void ) - Get differential pressure and temperature function. 
 *
 * @author Nenad Filipovic
 *
 */

#include "board.h"
#include "log.h"
#include "i2cisolator4.h"

#define I2CISOLATOR4_VAV_PRESS_DEV_ADDR                            0x5C
#define I2CISOLATOR4_VAV_PRESS_CMD_START_PRESSURE_CONVERSION       0x21
#define I2CISOLATOR4_VAV_PRESS_PRESS_SCALE_FACTOR                  1200
#define I2CISOLATOR4_VAV_PRESS_TEMP_SCALE_FACTOR                     72
#define I2CISOLATOR4_VAV_PRESS_READOUT_AT_KNOWN_TEMPERATURE         105
#define I2CISOLATOR4_VAV_PRESS_KNOWN_TEMPERATURE_C                   23.1

static i2cisolator4_t i2cisolator4;
static log_t logger;
static float diff_press;
static float temperature;

void get_dif_press_and_temp ( void ) {
    uint8_t rx_buf[ 4 ];
    int16_t readout_data;
    
    i2cisolator4_generic_read( &i2cisolator4, I2CISOLATOR4_VAV_PRESS_CMD_START_PRESSURE_CONVERSION, &rx_buf[ 0 ], 4 );
    
    readout_data = rx_buf[ 1 ];
    readout_data <<= 9;
    readout_data |= rx_buf[ 0 ];
    readout_data >>= 1;
    
    diff_press = ( float ) readout_data;
    diff_press /= I2CISOLATOR4_VAV_PRESS_PRESS_SCALE_FACTOR;
   
    readout_data = rx_buf[ 3 ];
    readout_data <<= 8;
    readout_data |= rx_buf[ 2 ];
    
    temperature = ( float ) readout_data;
    temperature -= I2CISOLATOR4_VAV_PRESS_READOUT_AT_KNOWN_TEMPERATURE;
    temperature /= I2CISOLATOR4_VAV_PRESS_TEMP_SCALE_FACTOR;
    temperature += I2CISOLATOR4_VAV_PRESS_KNOWN_TEMPERATURE_C;
    
}

void application_init ( void ) {
    log_cfg_t log_cfg;                    /**< Logger config object. */
    i2cisolator4_cfg_t i2cisolator4_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_info( &logger, " Application Init " );

    // Click initialization.

    i2cisolator4_cfg_setup( &i2cisolator4_cfg );
    I2CISOLATOR4_MAP_MIKROBUS( i2cisolator4_cfg, MIKROBUS_1 );
    err_t init_flag = i2cisolator4_init( &i2cisolator4, &i2cisolator4_cfg );
    if ( init_flag == I2C_MASTER_ERROR ) {
        log_error( &logger, " Application Init Error. " );
        log_info( &logger, " Please, run program again... " );

        for ( ; ; );
    }

    log_info( &logger, " Application Task " );
    Delay_ms( 100 );
    
    log_printf( &logger, "--------------------------------\r\n" );
    log_printf( &logger, "     Set I2C Slave Address      \r\n" );
    i2cisolator4_set_slave_address ( &i2cisolator4, I2CISOLATOR4_VAV_PRESS_DEV_ADDR );
    Delay_ms( 100 );
}

void application_task ( void ) {
    get_dif_press_and_temp( );
    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 );
}

void main ( void ) {
    application_init( );

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

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

Additional Support

Resources

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