Enhance your industrial processes with ADS1247 and ATmega644

RTDs - The path to temperature excellence

Published Nov 11, 2023

Click board™

RTD 2 Click

Dev. board

EasyAVR v7

Compiler

NECTO Studio

MCU

ATmega644

Discover how our RTD solution can provide you with accurate and reliable temperature measurements for your critical processes.

Hardware Overview

How does it work?

RTD 2 Click is based on the ADS1247, a highly integrated 24-bit data converter with a programmable gain amplifier (PGA) for sensor measurement applications from Texas Instruments. The ADS1247 includes a delta-sigma (ΔΣ) ADC with an adjustable single-cycle settling digital filter, an internal oscillator, and an SPI-compatible serial interface. It also has a flexible input multiplexer with system monitoring capability and general-purpose I/O settings, a very low-drift voltage reference, and two matched current sources for sensor excitation. The ADS1247 provides a system monitor function. This function can measure the analog power supply, digital power supply, external voltage reference, or ambient temperature. Note that the system monitor function provides a coarse result. When the system monitor is enabled, the analog inputs are disconnected. The two IDAC current sources integrated into the ADS1247 are used to implement the lead-wire compensation. One IDAC current source (IDAC1) provides excitation to the RTD element. The other current source (IDAC2)

has the same current setting, which cancels lead-wire resistance by generating a voltage drop across lead-wire resistance R2 equal to the voltage drop across the R1 resistor (9.09k). Because the voltage across the RTD is measured differentially at ADC pins AIN1 and AIN2 of the ADS1247, the voltages across the lead-wire resistances cancel. The ADC reference voltage (pins REFP0 and REFN0) is derived from the voltage across the R5 resistor with the currents from IDAC1 and IDAC2, providing ratiometric cancellation of current-source drift. R5 also level shifts the RTD signal to within the ADC-specified common-mode input range. The RTD 2 Click communicates with MCU using the standard SPI serial interface with an additional data-ready signal routed on the INT pin of the mikroBUS™ socket labeled as RDY. Data Ready signal indicates when a new conversion is complete, and the conversion result is stored in the conversion result buffer. It also has an active-low Reset signal routed on the RST pin of the mikroBUS™ used to reset the device and a precise conversion control signal routed on the AN pin of

the mikroBUS™ socket labeled as STR. The ADS1247 stays in Reset Mode as long as the RST pin stays low. When the RST pin goes high, the ADC comes out of Reset Mode and can convert data. This Click board™ can work only with 3-wire probe types that MIKROE offers, such as the PT100 type Platinum Probe, an RTD probe used to measure temperatures up to 250°C. Platinum is an excellent choice since they are very stable and reusable and are resistant to corrosion or oxidation. The measurement probe is connected to the RTD 2 Click by using the screw terminal on the top of the board, and it has wires that can be 1m long, which makes it possible to measure high temperatures from a safe distance. This Click board™ can be operated only with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. Also, it comes equipped with a library containing functions and an example code that can be used as a reference for further development.

Features overview

Development board

EasyAVR v7 is the seventh generation of AVR development boards specially designed for the needs of rapid development of embedded applications. It supports a wide range of 16-bit AVR microcontrollers from Microchip and has a broad set of unique functions, such as a powerful onboard mikroProg programmer and In-Circuit debugger over USB. 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, EasyAVR v7 allows you to connect accessory boards, sensors, and custom electronics more

efficiently than ever. Each part of the EasyAVR 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 a wide range of external power sources, including an external 12V power supply, 7-12V AC or 9-15V 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 which cover a wide range of 16-bit AVR MCUs. EasyAVR 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.

Microcontroller Overview

MCU Card / MCU

Architecture

AVR

MCU Memory (KB)

Silicon Vendor

Microchip

Pin count

RAM (Bytes)

4096

You complete me!

Accessories

The PT100 3-wire temperature probe is an advanced RTD platinum sensor designed for precise temperature measurement up to 250°C. Perfectly compatible with the RTD Click board™, this probe utilizes RTD sensors - thermosensitive resistors that adapt their resistance to temperature changes. The probe's core features a meticulously crafted strip of platinum with a resistance of 100Ω at 0°C, earning the designation PT100. Key features include a temperature range of up to 250⁰ Celsius, a 3-wire configuration for enhanced accuracy, a length of 1m (100cm, 3.37 inches), Grade 2B construction for durability, and a tight tolerance of 0.5". Whether in industrial or scientific settings, the PT100 3-wire temperature probe delivers reliable and precise temperature readings, ensuring optimal performance in diverse applications.

Used MCU Pins

mikroBUS™ mapper

Conversion Start

PA7

Reset

PA6

RST

SPI Chip Select

PA5

SPI Clock

PB7

SCK

SPI Data OUT

PB6

MISO

SPI Data IN

PB5

MOSI

Power Supply

3.3V

Ground

GND

PWM

Data-Ready

PD2

INT

SCL

SDA

Ground

GND

Take a closer look

Click board™ Schematic

Step by step

Project assembly

EasyAVR v7 front image hardware assembly

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

EasyAVR v7 Access DIP MB 1 - upright/background hardware assembly

NECTO Compiler Selection Step Image hardware assembly

Necto DIP image step 7 hardware assembly

EasyPIC PRO v7a Display Selection 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 RTD 2 Click driver.

Key functions:

rtd2_check_new_data_ready - The function check new data ready
rtd2_get_temperature - The function read output data and return ambient temperature from the PT100 3-wire temperature probe
rtd2_enable_start - The function enables ADC conversion

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 Rtd 2 Click example
 * 
 * # Description
 * RTD 2 Click board is commonly used for measuring ambient temperature
 * from the PT100 3-wire temperature probe.
 *
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * Initializes the driver, performs a hardware reset, and sets the click 
 * default configuration.
 * 
 * ## Application Task  
 * Reads an ambient temperature measured by the PT100 3-wire temperature probe
 * connected to the RTD 2 click board, and logs the results on the USB UART each second.
 * 
 * \author MikroE Team
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "rtd2.h"

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

static rtd2_t rtd2;
static log_t logger;
static float temperature;

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

void application_init ( void )
{
    log_cfg_t log_cfg;
    rtd2_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.

    rtd2_cfg_setup( &cfg );
    RTD2_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    rtd2_init( &rtd2, &cfg );

    Delay_ms( 200 );

    log_printf( &logger, "----- Hardware Reset ------\r\n" );
    rtd2_hw_reset( &rtd2 );
    Delay_ms( 100 );
    
    log_printf( &logger, "-- Default configuration --\r\n" );
    rtd2_default_cfg( &rtd2 );
    Delay_ms( 1000 );
    
    log_printf( &logger, "--------------------------\r\n" );
    log_printf( &logger, "     Start Measurement    \r\n" );
    log_printf( &logger, "--------------------------\r\n" );
    Delay_ms( 100 );
}

void application_task ( void )
{
    if ( rtd2_check_new_data_ready( &rtd2 ) == RTD2_NEW_DATA_IS_READY )
    {
        temperature = rtd2_get_temperature( &rtd2 );
        log_printf( &logger, " Temperature : %.2f C\r\n", temperature );
        log_printf( &logger, "--------------------------\r\n");
        Delay_ms( 1000 );
    }
    else
    {
        rtd2_enable_start( &rtd2, RTD2_START_CONVERSION_DISABLE );
        Delay_ms( 1000 );
    }
}

void main ( void )
{
    application_init( );

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


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