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Ensure secure I2C data exchange with ISO1540 and PIC18F26J11

Completely isolated, completely bidirectional I2C

I2C Isolator Click with EasyPIC v7

Published Nov 01, 2023

Click board™

I2C Isolator Click

Development board

EasyPIC v7

Compiler

NECTO Studio

MCU

PIC18F26J11

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

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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

EasyPIC v7 is the seventh generation of PIC development boards specially designed to develop embedded applications rapidly. It supports a wide range of 8-bit PIC microcontrollers from Microchip and has 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 in one place, such as switches, buttons, indicators, connectors, and others. With four different connectors for each port, EasyPIC v7 allows you to connect accessory boards, sensors, and custom electronics more efficiently than ever. Each part of

the EasyPIC 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 various external power sources, including an external 12V power supply, 7-23V AC or 9-32V DC via DC connector/screw terminals, and a power source via the USB Type-B (USB-B) connector. Communication options such as

USB-UART and RS-232 are also included, alongside the well-established mikroBUS™ standard, three display options (7-segment, graphical, and character-based LCD), and several different DIP sockets. These sockets cover a wide range of 8-bit PIC MCUs, from PIC10F, PIC12F, PIC16F, PIC16Enh, PIC18F, PIC18FJ, and PIC18FK families. EasyPIC 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 v7 horizontal image

Microcontroller Overview

MCU Card / MCU

default

Architecture

PIC

MCU Memory (KB)

64

Silicon Vendor

Microchip

Pin count

28

RAM (Bytes)

3800

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
RC3
SCL
I2C Data
RC4
SDA
Power Supply
5V
5V
Ground
GND
GND
2

Take a closer look

Schematic

I2C Isolator Click Schematic schematic

Step by step

Project assembly

EasyPIC v7 front image hardware assembly

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

EasyPIC v7 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 v7 Access MB 2 - 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
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

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 Click driver.

Key functions:

  • i2cisolator_generic_write - Generic write function

  • i2cisolator_generic_read - Generic read 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 
 * \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 );
}

void main ( void )
{
    application_init( );

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


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

Additional Support

Resources