Intermediate
30 min

Provide galvanic isolation of digital I2C signals with MAX14937 and PIC32MZ2048EFH144

Full i2C interface isolation

I2C Isolator 4 Click with EasyPIC Fusion v7

Published Mar 02, 2023

Click board™

I2C Isolator 4 Click

Dev Board

EasyPIC Fusion v7

Compiler

NECTO Studio

MCU

PIC32MZ2048EFH144

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

EasyPIC Fusion v7 is the seventh generation of PIC development boards specially designed to develop embedded applications rapidly. It supports a wide range of 16/32-bit PIC microcontrollers from Microchip and a broad set of unique functions, such as a powerful onboard mikroProg programmer and In-Circuit debugger over USB-B. 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. With two different connectors for each port, EasyPIC Fusion v7 allows you to connect accessory boards, sensors, and custom electronics more efficiently than ever. Each part of

the EasyPIC Fusion v7 development board contains the components necessary for the most efficient operation of the same board. An integrated mikroProg, a fast USB 2.0 programmer with mikroICD hardware In-Circuit Debugger, offers many valuable programming/debugging options and seamless integration with the Mikroe software environment. Besides it also includes a clean and regulated power supply block for the development board. It can use a wide range of external power sources, including an external 12V power supply, 7-12V AC or 9-15V DC via DC connector/screw terminals, and a power source via the USB Type-B (USB-B) connector. Communication options such

as USB-UART, USB-HOST, CAN, and Ethernet are also included, including the well-established mikroBUS™ standard, one display option for the TFT board line of products, and a standard TQFP socket for the seventh-generation MCU cards. This socket covers a wide range of 16-bit dsPIC/PIC24 and 32-bit PIC32 MCUs. EasyPIC Fusion v7 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 Fusion v7 horizontal image

Microcontroller Overview

MCU Card / MCU

default

Type

7th Generation

Architecture

PIC32

MCU Memory (KB)

2048

Silicon Vendor

Microchip

Pin count

144

RAM (Bytes)

524288

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
RA2
SCL
I2C Data
RA3
SDA
Power Supply
5V
5V
Ground
GND
GND
1

Take a closer look

Click board™ Schematic

I2C Isolator 4 Click Schematic schematic

Step by step

Project assembly

EasyPIC Fusion v7 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the EasyPIC Fusion v7 as your development board.

EasyPIC Fusion v7 front image hardware assembly
GNSS2 Click front image hardware assembly
EasyPIC FUSION v7 ETH MCUcard with PIC32MZ2048EFH144 front image hardware assembly
GNSS2 Click complete accessories setup image hardware assembly
EMxPRO-STM32-TIVA/EPIC Fusion v7 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
EasyPIC PRO v7a MCU Selection Necto Step hardware assembly
EasyPIC PRO v7a Display Selection Necto Step 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

This Click board can be interfaced and monitored in two ways:

  • Application Output - Use the "Application Output" window in Debug mode for real-time data monitoring. Set it up properly by following this tutorial.

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

The complete application code and a ready-to-use project are available through the NECTO Studio Package Manager for direct installation in the NECTO Studio. The application code can also be found on the MIKROE GitHub account.

/*!
 * @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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