Intermediate
30 min

Discover the enhanced security of a full-duplex RS-485 interface with ADM2867E and ATmega328P

The silent guardian of data integrity

RS485 Isolator 2 Click with Arduino UNO Rev3

Published Feb 14, 2024

Click board™

RS485 Isolator 2 Click

Dev. board

Arduino UNO Rev3

Compiler

NECTO Studio

MCU

ATmega328P

Full isolation and full-duplex communication - the combination that unlocks seamless data exchange without any compromises. Learn how it's done with RS485 transceiver.

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Hardware Overview

How does it work?

RS485 Isolator 2 Click is based on ADM2867E from Analog Devices. It includes a flexible integrated dc-to-dc converter optimized for low radiated emissions (EMI). The isolated dc-to-dc converter is constructed of a set of chip scale coplanar coils that are separated by an insulating material. By exciting the upper coil with an ac signal, power is magnetically coupled across the isolation barrier where it is rectified and regulated. Because no direct electrical connection exists between the top and bottom coil, the primary and secondary side of the device remain galvanically isolated. The integrated dc-to-dc converter is optimized to minimize radiated electromagnetic interference (EMI), and allows designers to meet the CISPR22/EN55022 Class B requirements on a 2-layer PCB. The ADM2867E features a proprietary transmitter architecture with a low driver output impedance, resulting in an increased differential

output voltage. This architecture is particularly useful when operating the device at lower data rates over long cable runs, where the dc resistance of the transmission line dominates signal attenuation. In these applications, the increased differential voltage extends the reach of the device to longer cable lengths. The RS485 Isolator 2 features separate digital logic pins, IND and INR, to correct cases where the driver and/or receiver are wired incorrectly. Use the IND pin to correct driver functionality when Y and Z are wired incorrectly. Use the INR pin to correct receiver functionality when A and B are wired incorrectly. When the receiver is inverted, the device maintains a Logic 1 receiver output with a 30 mV noise margin when inputs are shorted together or open circuit. The standard RS-485 receiver input impedance is 12 kΩ (1 unit load), and the standard driver can drive up to 32 unit loads. The ADM2867E transceiver has a

1/6 unit load receiver input impedance (72 kΩ), allowing up to 196 transceivers to be connected in parallel on one communication line. Any combination of these devices and other RS-485 transceivers with a total of 32 unit loads or fewer can be connected to the line.
The integrated isoPower isolated dc-to-dc converter requires up to 10 ms to power up to its set point of 3.3 V or 5 V. During this start-up time, it is not recommended to assert the DE driver enable signal. 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 as a reference for further development.

RS485 Isolator 2 Click top side image
RS485 Isolator 2 Click bottom side 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
Receiver Enable
PD2
RST
Driver Enable
PB2
CS
NC
NC
SCK
NC
NC
MISO
NC
NC
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
Receiver Inversion
PD6
PWM
Driver Inversion
PC3
INT
UART TX
PD0
TX
UART RX
PD1
RX
NC
NC
SCL
NC
NC
SDA
Power Supply
5V
5V
Ground
GND
GND
1

Take a closer look

Click board™ Schematic

RS485 Isolator 2 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 RS485 Isolator 2 Click driver.

Key functions:

  • rs485isolator2_send_bit_by_bit - Bit by bit write function.

  • rs485isolator2_set_re_pin - Set RE ( reset ) pin state.

  • rs485isolator2_set_de_pin - Set DE ( cs ) pin state.

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 Rs485Isolator2 Click example
 * 
 * # Description
 * This example reads and processes data from RS485 Isolator 2 clicks.
 *
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * Initializes the driver and enables the selected mode.
 * 
 * ## Application Task  
 * Depending on the selected mode, it reads all the received data or sends the desired message
 * every 2 seconds.
 * 
 * ## Additional Function
 * - rs485isolator2_process ( ) - The general process of collecting the received data.
 * 
 * @note
 * Wire connection guide : Driver(Master)       Slave
 *                                     Y   ->   A
 *                                     Z   ->   B
 * \author MikroE Team
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "rs485isolator2.h"
#include "string.h"

#define PROCESS_RX_BUFFER_SIZE 500

#define TEXT_TO_SEND "MikroE\r\n"

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

#define DEMO_APP_RECEIVER
// #define DEMO_APP_TRANSMITTER

static rs485isolator2_t rs485isolator2;
static log_t logger;

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

static void rs485isolator2_process ( void )
{
    int32_t rsp_size;
    
    char uart_rx_buffer[ PROCESS_RX_BUFFER_SIZE ] = { 0 };
    uint8_t check_buf_cnt;
    
    rsp_size = rs485isolator2_generic_read( &rs485isolator2, uart_rx_buffer, PROCESS_RX_BUFFER_SIZE );

    if ( rsp_size > 0 )
    {  
        log_printf( &logger, "Received data: " );
        
        for ( check_buf_cnt = 0; check_buf_cnt < rsp_size; check_buf_cnt++ )
        {
            log_printf( &logger, "%c", uart_rx_buffer[ check_buf_cnt ] );
        }
    }
    Delay_ms( 100 );
}

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

void application_init ( void )
{
    log_cfg_t log_cfg;
    rs485isolator2_cfg_t cfg;

    /** 
     * 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.

    rs485isolator2_cfg_setup( &cfg );
    RS485ISOLATOR2_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    rs485isolator2_init( &rs485isolator2, &cfg );
    Delay_ms( 100 );
    
#ifdef DEMO_APP_RECEIVER
    rs485isolator2_set_re_pin( &rs485isolator2, RS485ISOLATOR2_ENABLE_RE );
    rs485isolator2_set_de_pin( &rs485isolator2, RS485ISOLATOR2_DISABLE_DE );
    log_info( &logger, "---- Receiver mode ----" );
#endif    
#ifdef DEMO_APP_TRANSMITTER
    rs485isolator2_set_de_pin( &rs485isolator2, RS485ISOLATOR2_ENABLE_DE );
    rs485isolator2_set_re_pin( &rs485isolator2, RS485ISOLATOR2_DISABLE_RE );
    log_info( &logger, "---- Transmitter mode ----" );
#endif    
    Delay_ms( 100 );
}

void application_task ( void )
{
#ifdef DEMO_APP_RECEIVER
    rs485isolator2_process( );
#endif    
    
#ifdef DEMO_APP_TRANSMITTER
    rs485isolator2_generic_write( &rs485isolator2, TEXT_TO_SEND, 8 );
    log_info( &logger, "---- Data sent ----" );
    Delay_ms( 2000 );
#endif    
}

void main ( void )
{
    application_init( );

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


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

Additional Support

Resources

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