Intermediate
30 min
0

Provide galvanic isolation of digital I2C signals with MAX14937 and STM32F215ZG

Full i2C interface isolation

I2C Isolator 4 Click with Fusion for STM32 v8

Published Mar 02, 2023

Click board™

I2C Isolator 4 Click

Development board

Fusion for STM32 v8

Compiler

NECTO Studio

MCU

STM32F215ZG

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

Fusion for STM32 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 32-bit ARM® Cortex®-M based MCUs from STMicroelectronics, 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, Fusion for STM32 v8 provides a fluid and immersive working experience, allowing

access anywhere and under any circumstances at any time. Each part of the Fusion for STM32 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. Fusion for STM32 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.

Fusion for STM32 v8 horizontal image

Microcontroller Overview

MCU Card / MCU

default

Type

8th Generation

Architecture

ARM Cortex-M3

MCU Memory (KB)

1024

Silicon Vendor

STMicroelectronics

Pin count

144

RAM (Bytes)

131072

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
PB8
SCL
I2C Data
PB9
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

Fusion for PIC v8 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the Fusion for STM32 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 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