Beginner
10 min

Ensure secure I2C data exchange with ISO1540 and ATmega328P

Completely isolated, completely bidirectional I2C

I2C Isolator Click with Arduino UNO Rev3

Published Feb 14, 2024

Click board™

I2C Isolator Click

Dev. board

Arduino UNO Rev3

Compiler

NECTO Studio

MCU

ATmega328P

Take your engineering solution to the next level with isolated bidirectional I2C-compatible communication

A

A

Hardware Overview

How does it work?

I2C Isolator Click is based on the ISO1540, a 2.5kVrms I2C digital isolator from Texas Instruments. The ISO1540 enables a completely isolated I2C interface, supporting Fast Mode Plus up to 1MHz, with two isolated bidirectional channels for clock and data lines. It provides advantages such as performance, size, and power consumption compared to optocouplers, which makes it suitable for multi-master and applications where slave clock stretching is possible. Isolated bidirectional communication is accomplished by offsetting the low-level output

voltage on the MCU side to a value greater than its high-level input voltage, preventing an internal logic latch that would occur with standard digital isolators. The ISO1540 has logic input and output buffers separated by Texas Instruments Capacitive Isolation technology using a silicon dioxide (SiO2) barrier. Also, the ISO1540 internally splits a bidirectional line into two unidirectional lines, each isolated through a single-channel digital isolator. This way, each channel output is made open-drain to comply with the open-drain technology of I2C. When used with isolated

power supplies, the ISO1540 blocks high voltages, isolates grounds, and prevents noise currents from entering the local ground and interfering with or damaging sensitive circuitry. This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the VCC1 SEL jumper. Therefore, both 3.3V and 5V capable MCUs to use the communication lines properly. 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 Click hardware overview image

Features overview

Development board

Arduino UNO is a versatile microcontroller board built around the ATmega328P chip. It offers extensive connectivity options for various projects, featuring 14 digital input/output pins, six of which are PWM-capable, along with six analog inputs. Its core components include a 16MHz ceramic resonator, a USB connection, a power jack, an

ICSP header, and a reset button, providing everything necessary to power and program the board. The Uno is ready to go, whether connected to a computer via USB or powered by an AC-to-DC adapter or battery. As the first USB Arduino board, it serves as the benchmark for the Arduino platform, with "Uno" symbolizing its status as the

first in a series. This name choice, meaning "one" in Italian, commemorates the launch of Arduino Software (IDE) 1.0. Initially introduced alongside version 1.0 of the Arduino Software (IDE), the Uno has since become the foundational model for subsequent Arduino releases, embodying the platform's evolution.

Arduino UNO Rev3 double side image

Microcontroller Overview

MCU Card / MCU

default

Architecture

AVR

MCU Memory (KB)

32

Silicon Vendor

Microchip

Pin count

28

RAM (Bytes)

2048

You complete me!

Accessories

Click Shield for Arduino UNO has two proprietary mikroBUS™ sockets, allowing all the Click board™ devices to be interfaced with the Arduino UNO board without effort. The Arduino Uno, a microcontroller board based on the ATmega328P, provides an affordable and flexible way for users to try out new concepts and build prototypes with the ATmega328P microcontroller from various combinations of performance, power consumption, and features. The Arduino Uno has 14 digital input/output pins (of which six can be used as PWM outputs), six analog inputs, a 16 MHz ceramic resonator (CSTCE16M0V53-R0), a USB connection, a power jack, an ICSP header, and reset button. Most of the ATmega328P microcontroller pins are brought to the IO pins on the left and right edge of the board, which are then connected to two existing mikroBUS™ sockets. This Click Shield also has several switches that perform functions such as selecting the logic levels of analog signals on mikroBUS™ sockets and selecting logic voltage levels of the mikroBUS™ sockets themselves. Besides, the user is offered the possibility of using any Click board™ with the help of existing bidirectional level-shifting voltage translators, regardless of whether the Click board™ operates at a 3.3V or 5V logic voltage level. Once you connect the Arduino UNO board with our Click Shield for Arduino UNO, you can access hundreds of Click boards™, working with 3.3V or 5V logic voltage levels.

Click Shield for Arduino UNO accessories 1 image

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
PC5
SCL
I2C Data
PC4
SDA
Power Supply
5V
5V
Ground
GND
GND
1

Take a closer look

Click board™ Schematic

I2C Isolator Click Schematic schematic

Step by step

Project assembly

Click Shield for Arduino UNO front image hardware assembly

Start by selecting your development board and Click board™. Begin with the Arduino UNO Rev3 as your development board.

Click Shield for Arduino UNO front image hardware assembly
Arduino UNO Rev3 front image hardware assembly
Charger 27 Click front image hardware assembly
Prog-cut hardware assembly
Charger 27 Click complete accessories setup image hardware assembly
Arduino UNO Rev3 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 image step 5 hardware assembly
Necto image step 6 hardware assembly
Arduino UNO 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

1. Application Output - In Debug mode, the 'Application Output' window enables real-time data monitoring, offering direct insight into execution results. Ensure proper data display by configuring the environment correctly using the provided tutorial.

2. UART Terminal - Use the UART Terminal to monitor data transmission via a USB to UART converter, allowing direct communication between the Click board™ and your development system. Configure the baud rate and other serial settings according to your project's requirements to ensure proper functionality. For step-by-step setup instructions, refer to the provided tutorial.

3. Plot Output - The Plot feature offers a powerful way to visualize real-time sensor data, enabling trend analysis, debugging, and comparison of multiple data points. To set it up correctly, follow the provided tutorial, which includes a step-by-step example of using the Plot feature to display Click board™ readings. To use the Plot feature in your code, use the function: plot(*insert_graph_name*, variable_name);. This is a general format, and it is up to the user to replace 'insert_graph_name' with the actual graph name and 'variable_name' with the parameter to be displayed.

Software Support

Library Description

This library contains API for I2C Isolator Click driver.

Key functions:

  • i2cisolator_generic_write - Generic write function

  • i2cisolator_generic_read - Generic read 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 
 * \brief I2Cisolator Click example
 * 
 * # Description
 * This is an example which demonstrates the use of I2C Isolator Click board.
 *
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * Initialization driver enables - I2C,
 * sets configuration of TMP007 sensor on IrThermo 2 Click and start to write log.
 * 
 * ## Application Task  
 * In this example we use IrThermo 2 Click, measures the temperature with,
 * and calculate the temperature in degrees Celsius [ C ].
 * Results are being sent to the USART Terminal where you can track their changes.
 * All data logs on usb uart each second.
 * 
 * 
 * \author MikroE Team
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "i2cisolator.h"

/* Register Address */
#define I2CISOLATOR_IRTHERMO2_CONFIGURATION                       0x02
#define I2CISOLATOR_IRTHERMO2_OBJECT_TEMPERATURE              0x03
#define I2CISOLATOR_IRTHERMO2_STATUS_MASK_AND_ENABLE       0x05

/* Commands */       
#define I2CISOLATOR_IRTHERMO2_CFG_MODEON                           0x1000
#define I2CISOLATOR_IRTHERMO2_CFG_ALERTEN                           0x0100
#define I2CISOLATOR_IRTHERMO2_CFG_TRANSC                            0x0040
#define I2CISOLATOR_IRTHERMO2_CFG_16SAMPLE                         0x0800
#define I2CISOLATOR_IRTHERMO2_STAT_ALERTEN                         0x8000
#define I2CISOLATOR_IRTHERMO2_STAT_CRTEN                            0x4000

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

static i2cisolator_t i2cisolator;
static log_t logger;
static float temperature;

// ------------------------------------------------------- ADDITIONAL FUNCTIONS

void i2cisolator_get_temperature ( void )
{
    uint8_t temp_data[ 2 ];
    uint16_t temp;
    
    i2cisolator_generic_read( &i2cisolator, I2CISOLATOR_IRTHERMO2_OBJECT_TEMPERATURE, temp_data, 2 );
    
    temp = temp_data[ 0 ];
    temp <<= 8;
    temp |= temp_data[ 1 ];
    temp >>= 2;
    temperature = ( float ) temp;
    temperature *= 0.03125;
}

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

void application_init ( void )
{
    log_cfg_t log_cfg;
    i2cisolator_cfg_t cfg;
    uint8_t tmp;

    /** 
     * 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.

    i2cisolator_cfg_setup( &cfg );
    I2CISOLATOR_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    i2cisolator_init( &i2cisolator, &cfg );

    log_printf( &logger, "    Driver  Initialized\r\n" );
    log_printf( &logger, "---------------------------\r\n" );
    Delay_ms ( 100 );
    
    tmp =    I2CISOLATOR_IRTHERMO2_CFG_MODEON |
                I2CISOLATOR_IRTHERMO2_CFG_ALERTEN | 
                I2CISOLATOR_IRTHERMO2_CFG_TRANSC | 
                I2CISOLATOR_IRTHERMO2_CFG_16SAMPLE;
    i2cisolator_generic_write( &i2cisolator, I2CISOLATOR_IRTHERMO2_CONFIGURATION, &tmp, 1 );

    tmp =    I2CISOLATOR_IRTHERMO2_STAT_ALERTEN | 
                I2CISOLATOR_IRTHERMO2_STAT_CRTEN;
    i2cisolator_generic_write( &i2cisolator, I2CISOLATOR_IRTHERMO2_STATUS_MASK_AND_ENABLE, &tmp, 1 );    
    
    log_printf( &logger, "       Configuration\r\n" );
    log_printf( &logger, "      IrThermo 2 Click\r\n" );
    log_printf( &logger, "---------------------------\r\n" );
    Delay_ms ( 100 );
}

void application_task ( void )
{
    i2cisolator_get_temperature( );   
    
    log_printf( &logger, " Temperature : %0.2f C\r\n", temperature );
    log_printf( &logger, "---------------------------\r\n" );
    Delay_ms ( 1000 );
}

int main ( void ) 
{
    /* Do not remove this line or clock might not be set correctly. */
    #ifdef PREINIT_SUPPORTED
    preinit();
    #endif
    
    application_init( );
    
    for ( ; ; ) 
    {
        application_task( );
    }

    return 0;
}


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

Additional Support

Resources

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