Achieve completely isolated bidirectional I2C communication with ADuM1252 and PIC18F4515

Reliable and high-speed data transfer with the added benefit of isolation

Published Dec 22, 2023

Click board™

I2C Isolator 7 Click

Dev. board

EasyPIC v8

Compiler

NECTO Studio

MCU

PIC18F4515

Help devices from different "worlds" (with different power sources or electrical characteristics) to talk to each other safely and consistently

Hardware Overview

How does it work?

I2C Isolator 7 Click is based on the ADuM1252, an ultra-low power, bidirectional I2C isolator from Analog Devices. It features independent power supplies on both sides. Side 1 is reserved for 3.3V and 5V of mikroBUS™ socket rails, while side 2 can be supplied in a range of 1.71V up to 5.5V. To prevent latch-up action, its side 1 outputs comprise a special buffer that regulates the logic-low voltage, and the input logic-low threshold is

lower than the output logic-low voltage. In addition, side 2 features conventional buffers that do not regulate logic-low output voltage. I2C Isolator 7 Click uses a standard 2-Wire I2C interface to allow the host MCU to have an isolated bidirectional data transfer with a connected I2C device to the I2C terminals. As we mentioned, besides the I2C bus, the power supply is isolated, too. Places for optional pull-ups on the I2C bus are

left unpopulated. You can solder resistors according to your needs. 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. Also, this Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used for further development.

I2C Isolator 7 Click hardware overview image

Features overview

Development board

EasyPIC v8 is a development board specially designed for the needs of rapid development of embedded applications. It supports many high pin count 8-bit PIC microcontrollers from Microchip, regardless of their number of pins, and a broad set of unique functions, such as the first-ever embedded debugger/programmer. 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, EasyPIC v8 provides a fluid and immersive working experience, allowing access anywhere and under any

circumstances at any time. Each part of the EasyPIC v8 development board contains the components necessary for the most efficient operation of the same board. In addition to the advanced integrated CODEGRIP programmer/debugger module, which offers many valuable programming/debugging options and seamless integration with the Mikroe software environment, the board 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 DEVICE, and CAN are also included, including the well-established mikroBUS™ standard, two display options (graphical and character-based LCD), and several different DIP sockets. These sockets cover a wide range of 8-bit PIC MCUs, from the smallest PIC MCU devices with only eight up to forty pins. EasyPIC 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.

Microcontroller Overview

MCU Card / MCU

Architecture

PIC

MCU Memory (KB)

Silicon Vendor

Microchip

Pin count

RAM (Bytes)

3968

Used MCU Pins

mikroBUS™ mapper

RST

ID COMM

RE0

SCK

MISO

MOSI

Power Supply

3.3V

Ground

GND

PWM

INT

I2C Clock

RC3

SCL

I2C Data

RC4

SDA

Power Supply

Ground

GND

Take a closer look

Click board™ Schematic

I2C Isolator 7 Click Schematic schematic

Step by step

Project assembly

EasyPIC v8 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the EasyPIC v8 as your development board.

NECTO Output Selection Step Image hardware assembly

In the advanced settings, pay special attention to the Redirect standard output field. By default, it is set to Application output as the method of displaying final results. To show results via a UART terminal, select the “UART” option in that field and click the “SAVE” button. You will be returned to the Compiler field, and now you can move on to the next step by pressing the “NEXT” button.

GNSS2 Click front image hardware assembly

GNSS2 Click complete accessories setup image hardware assembly

EasyPIC v8 Access DIPMB 1 - upright/background hardware assembly

NECTO Compiler Selection Step Image hardware assembly

Necto DIP image step 7 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 7 Click driver.

Key functions:

i2cisolator7_generic_write - This function shall generate a START signal, followed by len number of writes from data_in.
i2cisolator7_generic_read - This function shall generate a START signal, followed by len number of reads from the bus placing the data in data_out.
i2cisolator7_write_then_read - This function performs a write operation followed by a read operation on the bus by using I2C serial interface.

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 I2C Isolator 7 Click example
 *
 * # Description
 * This demo application shows an example of an I2C Isolator 7 Click 
 * wired to the PRESS Click board™ for reading device ID (Who am I).
 * The library also includes an I2C writing and reading functions.
 *
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * The initialization of I2C module and log UART.
 * After driver initialization, the app sets the PRESS Click board™ slave address.
 *
 * ## Application Task
 * This example demonstrates the use of the I2C Isolator 7 Click board™.
 * Logs device ID values of the PRESS Click board™ 
 * wired to the I2C Isolator 7 Click board™.
 *
 *
 * @author Nenad Filipovic
 *
 */

#include "board.h"
#include "log.h"
#include "i2cisolator7.h"

#define PRESS_DEVICE_ADDRESS               0x5C
#define PRESS_REG_WHO_AM_I                 0x0F
#define PRESS_WHO_AM_I                     0xB4

static i2cisolator7_t i2cisolator7;
static log_t logger;

void application_init ( void ) 
{
    log_cfg_t log_cfg;  /**< Logger config object. */
    i2cisolator7_cfg_t i2cisolator7_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.
    i2cisolator7_cfg_setup( &i2cisolator7_cfg );
    I2CISOLATOR7_MAP_MIKROBUS( i2cisolator7_cfg, MIKROBUS_1 );
    if ( I2C_MASTER_ERROR == i2cisolator7_init( &i2cisolator7, &i2cisolator7_cfg ) ) 
    {
        log_error( &logger, " Communication init." );
        for ( ; ; );
    }
    Delay_ms ( 100 );
    
    if ( I2CISOLATOR7_ERROR == i2cisolator7_set_slave_address( &i2cisolator7, PRESS_DEVICE_ADDRESS ) )
    {
        log_error( &logger, " Set I2C Slave address ERROR." );
        for ( ; ; );
    }
    Delay_ms ( 100 );

    log_info( &logger, " Application Task " );
    log_printf( &logger, "---------------------\r\n" );
    Delay_ms ( 100 );
}

void application_task ( void ) 
{
    uint8_t device_id = 0;
    uint8_t reg = PRESS_REG_WHO_AM_I;
    if ( I2CISOLATOR7_OK == i2cisolator7_write_then_read( &i2cisolator7, &reg, 1, &device_id, 1 ) )
    {
        if ( PRESS_WHO_AM_I == device_id )
        {
            log_printf( &logger, " Device ID: 0x%.2X\r\n", ( uint16_t ) device_id );
            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