Convert analog to digital signals with AD7091R and ATmega328 with additional electrical isolation between them

Isolate and digitize with precision

Published Feb 14, 2024

Click board™

ISO ADC 2 Click

Dev. board

Arduino UNO Rev3

Compiler

NECTO Studio

MCU

ATmega328

Unleash the power of isolation with our cutting-edge A/D converter!

Hardware Overview

How does it work?

ISO ADC 2 Click is based on the AD7091R, a 12-bit successive-approximation analog-to-digital converter (ADC) with an isolated DC-DC converter from Analog Devices. This Click board™ allows single-supply operation and consists of active Analog Devices components: AD8616, a level shifting circuit; AD7091R, an ADC stage; and ADuM5401, an output isolation stage. The AD8616 is chosen for this application because of its low offset voltage, low bias current, and low noise. The output of the OpAmp is 0.1V to 2.4V, which matches the input range of the ADC (0V to 2.5V) with a 100mV safety margin to maintain linearity. A single-pole RC filter (R2/C9) follows the OpAmp output stage to reduce the out-of-band noise. The next part of the circuit is the AD7091R, ADC chosen because of its

ultralow power, which is significantly lower than any competitive A/D converter. It features a power-down option, implemented across the serial interface to save power between conversions, described in the Modes of Operation section in the datasheet. After a successful conversion, the ADC sends the data to the MCU through galvanic isolation provided by the ADuM5401 quad-channel digital isolator with an integrated DC-DC converter. The isolator has a secondary side controller architecture with isolated pulse-width modulation (PWM) feedback, and it works on the principle common to most switching power supplies. The ISO ADC 2 Click communicates with MCU using the 3-wire SPI serial interface that operates at clock rates up to 50MHz used for accessing data from the result register

and controlling the device's modes of operation. The CONVST signal of the AD7091R routed to the RST pin on the mikroBUS™ is used to initiate the conversion process, data acquisition, and select the operation mode. This ADC requires the user to initiate a software reset upon Power-Up, and it should be noted that failure to apply the correct software reset command may result in a device malfunction. 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. 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 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.

Microcontroller Overview

MCU Card / MCU

Architecture

AVR

MCU Memory (KB)

Silicon Vendor

Microchip

Pin count

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.

Used MCU Pins

mikroBUS™ mapper

Conversion Initialization

PD2

RST

SPI Chip Select

PB2

SPI Clock

PB5

SCK

SPI Data OUT

PB4

MISO

MOSI

Power Supply

3.3V

Ground

GND

PWM

INT

SCL

SDA

Power Supply

Ground

GND

Take a closer look

Click board™ 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.

Arduino UNO Rev3 front image hardware assembly

Charger 27 Click front image hardware assembly

Charger 27 Click complete accessories setup image hardware assembly

Arduino UNO Rev3 Access MB 1 - upright/background 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 ISO ADC 2 Click driver.

Key functions:

uint16_t isoadc2_read_adc ( void ) Function for reading 12bit ADC data
uint16_t isoadc2_get_mv ( uint16_t adc_data ) Function for converting ADC to mV data

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 IsoAdc2 Click example
 *
 * # Description
 * This is an example that demonstrates the use of the ISO ADC 2 Click board.
 *
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * Initialization of SPI module and additional GPIO pins.
 *
 * ## Application Task
 * Every second reads ADC data and voltage in mV and logs result.
 *
 * @author Stefan Ilic
 *
 */

#include "board.h"
#include "log.h"
#include "isoadc2.h"

static isoadc2_t isoadc2;
static log_t logger;

void application_init ( void ) {
    log_cfg_t log_cfg;  /**< Logger config object. */
    isoadc2_cfg_t isoadc2_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.

    isoadc2_cfg_setup( &isoadc2_cfg );
    ISOADC2_MAP_MIKROBUS( isoadc2_cfg, MIKROBUS_1 );
    err_t init_flag  = isoadc2_init( &isoadc2, &isoadc2_cfg );
    if ( SPI_MASTER_ERROR == init_flag ) {
        log_error( &logger, " Application Init Error. " );
        log_info( &logger, " Please, run program again... " );

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

void application_task ( void ) {
    uint16_t rx_data;
    uint16_t mv_data;
    
    isoadc2_read_adc( &isoadc2, &rx_data );
    Delay_ms( 100 );
    isoadc2_get_mv( &isoadc2, &mv_data );
    
    log_printf( &logger, " ADC: %d \r\n", rx_data );
    log_printf( &logger, " VIN: %d mV\r\n", mv_data );
    log_printf( &logger, "---------------\r\n" );

    Delay_ms( 1000 );
}

void main ( void ) {
    application_init( );

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

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