Expand the general-purpose input/output capabilities of ATmega2560 with DS2408

For projects that require more I/O ports than what the MCU natively supports

Expand 3 Click with Arduino Mega 2560 Rev3

Published Mar 08, 2024

Click board™

Expand 3 Click

Dev. board

Arduino Mega 2560 Rev3

Compiler

NECTO Studio

MCU

ATmega2560

Enhance your projects with the easy-to-use I/O expander that adds more functionality to any MCU through a simple 1-Wire interface

Hardware Overview

How does it work?

Expand 3 Click is based on the DS2408, an 8-channel programmable I/O expander from Analog Devices. The DS2408 has a factory-lasered 64-bit registration number that connects multiple same Click boards™ to the same data line. It communicates with the host MCU through a standard Dallas Semiconductor 1-Wire interface (15.3kbps or 100kbps), with PIO outputs configured as open-drain, providing a maximum on-resistance of 100Ω. A robust PIO channel-access communication protocol ensures that PIO output-setting changes occur error-free. It is suitable for latching PIO logic states into external circuitry, such as a D/A converter (DAC) or microcontroller data bus. This Click board™ communicates with MCU using the 1-Wire interface that, by definition,

requires only one data line (and ground) for communication with MCU. In the absence of a main power supply, the data line can also power the sensor parasitically. The 1-Wire communication line is routed to the GP SEL jumper, allowing the 1-Wire communication signal to the PWM pin or the AN pin of the mikroBUS™ socket. These pins are labeled OW0 and OW1, respectively, the same as the SMD jumper positions, making selecting the desired pin straightforward. Besides, the user is provided with the possibility of external use of the data line (OW) through the unpopulated header in the manner and needs that best suit the desired application, alongside a reset feature. Each DS2408 has its own unalterable and unique 64-bit ROM registration number that is, as mentioned, factory-lasered into

the chip. The registration number guarantees unique identification and addresses the device in a multidrop 1-Wire net environment. Multiple DS2408 devices can reside on a common 1-Wire bus and can operate independently of each other. The DS2408 also supports 1-Wire conditional search capability based on programmable PIO conditions or Power-on-Reset activity. This Click board™ can operate with both 3.3V and 5V logic voltage levels selected via the PWR 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.

Features overview

Development board

Arduino Mega 2560 is a robust microcontroller platform built around the ATmega 2560 chip. It has extensive capabilities and boasts 54 digital input/output pins, including 15 PWM outputs, 16 analog inputs, and 4 UARTs. With a 16MHz crystal

oscillator ensuring precise timing, it offers seamless connectivity via USB, a convenient power jack, an ICSP header, and a reset button. This all-inclusive board simplifies microcontroller projects; connect it to your computer via USB or power it up

using an AC-to-DC adapter or battery. Notably, the Mega 2560 maintains compatibility with a wide range of shields crafted for the Uno, Duemilanove, or Diecimila boards, ensuring versatility and ease of integration.

Arduino Mega 2560 Rev3 double side image

Microcontroller Overview

MCU Card / MCU

Architecture

AVR

MCU Memory (KB)

256

Silicon Vendor

Microchip

Pin count

100

RAM (Bytes)

8192

You complete me!

Accessories

Click Shield for Arduino Mega comes equipped with four mikroBUS™ sockets, with two in the form of a Shuttle connector, allowing all the Click board™ devices to be interfaced with the Arduino Mega board with no effort. Featuring an AVR 8-bit microcontroller with advanced RISC architecture, 54 digital I/O pins, and Arduino™ compatibility, the Arduino Mega board offers limitless possibilities for prototyping and creating diverse applications. This board is controlled and powered conveniently through a USB connection to program and debug the Arduino Mega board efficiently out of the box, with an additional USB cable connected to the USB B port on the board. Simplify your project development with the integrated ATmega16U2 programmer and unleash creativity using the extensive I/O options and expansion capabilities. There are eight switches, which you can use as inputs, and eight LEDs, which can be used as outputs of the MEGA2560. In addition, the shield features the MCP1501, a high-precision buffered voltage reference from Microchip. This reference is selected by default over the EXT REF jumper at the bottom of the board. You can choose an external one, as you would usually do with an Arduino Mega board. There is also a GND hook for testing purposes. Four additional LEDs are PWR, LED (standard pin D13), RX, and TX LEDs connected to UART1 (mikroBUS™ 1 socket). 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 Mega board with Click Shield for Arduino Mega, you can access hundreds of Click boards™, working with 3.3V or 5V logic voltage levels.

Used MCU Pins

mikroBUS™ mapper

1-Wire Data IN/OUT

PF1

Reset

PL1

RST

SCK

MISO

MOSI

Power Supply

3.3V

Ground

GND

1-Wire Data IN/OUT

PE4

PWM

INT

SCL

SDA

Power Supply

Ground

GND

Take a closer look

Click board™ Schematic

Step by step

Project assembly

Click Shield for Arduino Mega front image hardware assembly

Start by selecting your development board and Click board™. Begin with the Arduino Mega 2560 Rev3 as your development board.

Arduino Mega 2560 Rev3 front image hardware assembly

Charger 27 Click front image hardware assembly

Charger 27 Click complete accessories setup image hardware assembly

Board mapper by product8 hardware assembly

Necto No Display image step 8 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 Expand 3 Click driver.

Key functions:

expand3_write_state - This function writes data to the PIO output-latch state register which controls the open-drain output transistors of the PIO channels
expand3_read_last_state - This function reads the latest data written to the PIO using
expand3_read_current_state - This function reads the current logic state of the PIO pins

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 Expand 3 Click Example.
 *
 * # Description
 * This example demonstrates the use of Expand 3 Click board by setting and
 * reading the port state.
 *
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * Initializes the driver and performs the Click default configuration.
 *
 * ## Application Task
 * Writes a counter data to the port output pins and reads the status of the same port
 * input pins approximately every 500ms. All data are displayed on the USB UART.
 * 
 * @note
 * The PIO pins are in the open-drain mode, therefore a pull-up resistor must be added
 * to each pin. This Click board can be used in a combination with an EasyLED [MIKROE-571]
 * and EasyPULL [MIKROE-575] boards.
 *
 * @author Stefan Filipovic
 *
 */

#include "board.h"
#include "log.h"
#include "expand3.h"

static expand3_t expand3;
static log_t logger;

void application_init ( void ) 
{
    log_cfg_t log_cfg;  /**< Logger config object. */
    expand3_cfg_t expand3_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.
    expand3_cfg_setup( &expand3_cfg );
    EXPAND3_MAP_MIKROBUS( expand3_cfg, MIKROBUS_1 );
    if ( ONE_WIRE_ERROR == expand3_init( &expand3, &expand3_cfg ) ) 
    {
        log_error( &logger, " Communication init." );
        for ( ; ; );
    }
    
    if ( EXPAND3_ERROR == expand3_default_cfg ( &expand3 ) )
    {
        log_error( &logger, " Default configuration." );
        for ( ; ; );
    }

    log_info( &logger, " Application Task " );
}

void application_task ( void ) 
{
    static uint8_t out_state = 0;
    static uint8_t in_state = 0;
    if ( ( EXPAND3_OK == expand3_write_state ( &expand3, out_state ) ) && 
         ( EXPAND3_OK == expand3_read_last_state ( &expand3, &out_state ) ) )
    {
        log_printf( &logger, " Output state: 0x%.2X\r\n\n", out_state++ );
    }
    if ( EXPAND3_OK == expand3_read_current_state ( &expand3, &in_state ) )
    {
        log_printf( &logger, " Input state: 0x%.2X\r\n\n", in_state );
    }
    Delay_ms ( 500 );
}

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