Beginner
10 min

Get in sync with mother nature uaing DHT22 and ATmega328P

Stay ahead of the weather

DHT22 Click with Arduino UNO Rev3

Published Feb 14, 2024

Click board™

DHT22 Click

Dev. board

Arduino UNO Rev3

Compiler

NECTO Studio

MCU

ATmega328P

Our temperature and humidity sensing solution delivers the data you need for informed decision-making, risk assessment, and proactive maintenance, enabling you to take timely actions and ensure optimal conditions in any setting

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Hardware Overview

How does it work?

DHT22 Click is based on the DHT22, a digital humidity sensor with an integrated temperature sensor and a calibrated output signal from Aosong Electronics. The DHT22 utilizes an exclusive digital-signal-collecting technique and humidity sensing technology, assuring its reliability and stability. It can read humidity over the full range of 0 to 100% RH with a typical accuracy of ±2-5%, while its maximum temperature range is from -40 to 80°C with a typical accuracy of ±0.5°C. As mentioned, the DHT22 uses a capacitive humidity sensor and

a thermistor to measure the surrounding air, providing a digital signal for the host controller on one of the two possible mikroBUS™ pins, CS and Int pins of the mikroBUS™ socket marked as SD1 and SD2. An onboard SMD jumper labeled as SDA SEL can select the desirable processing line, placing it in an appropriate position marked as SDA1 or SDA2. This Click board™ only requires careful timing to grab the data. The DHT22 can only get new data once every two seconds, meaning the sensor readings can be up to two

seconds old. This Click board™ can operate with both 3.3V and 5V logic voltage levels selected via the PWR SEL jumper. This way, it is allowed for both 3.3V and 5V capable MCUs to 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.

DHT22 Click hardware overview 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
NC
NC
RST
Data Signal
PB2
CS
NC
NC
SCK
NC
NC
MISO
NC
NC
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
NC
NC
PWM
Data Signal
PC3
INT
NC
NC
TX
NC
NC
RX
NC
NC
SCL
NC
NC
SDA
Power Supply
5V
5V
Ground
GND
GND
1

Take a closer look

Click board™ Schematic

DHT22 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
Barometer 13 Click front image hardware assembly
Prog-cut hardware assembly
Arduino UNO Rev3 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 DHT22 Click driver.

Key functions:

  • dht22_start_signal - Sends start signal to the sensor function

  • dht22_check_sensor_response - Release the bus to wait the sensor response signal function

  • dht22_get_sensor_data - Reading data from the sensor function

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 DHT22 Click example
 *
 * # Description
 * This is a example which demonstrates the use of DHT22 Click board by
 * measuring temperature and relative humidity.
 *
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * Initializes the SDA data pin depending on the selected GPIO pin (SDA1/SDA2)
 * and log module.
 *
 * ## Application Task
 * Reads the temperature and humidity from the sensor and 
 * displays the values on the USB UART.
 *
 * \author Nemanja Medakovic
 *
 */

#include "board.h"
#include "log.h"
#include "dht22.h"

static dht22_t dht22;
static log_t logger;

void application_init ( void )
{
    log_cfg_t log_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... ----" );

    dht22_cfg_t dht22_cfg;

    //  Click initialization.

    dht22_cfg_setup( &dht22_cfg );
    DHT22_MAP_MIKROBUS( dht22_cfg, MIKROBUS_1 );

    if ( dht22_init( &dht22, &dht22_cfg ) == DHT22_ERROR )
    {
        log_info( &logger, "---- Application Init Error. ----" );
        log_info( &logger, "---- Please, run program again... ----" );

        for ( ; ; );
    }

    log_info( &logger, "---- Application Init done. ----" );
}

void application_task ( void )
{
    uint8_t resp_stat = DHT22_RESP_NOT_READY;
    uint32_t sens_meas = 0;
    float dht22_temp = 0;
    float dht22_hum = 0;
    
    dht22_init_sda_output( &dht22 );
    
    if ( dht22_start_signal( &dht22 ) == DHT22_OK )
    {
        dht22_init_sda_input( &dht22 );
        
        if ( dht22_check_sensor_response( &dht22, &resp_stat ) == DHT22_OK )
        {
            if ( resp_stat == DHT22_RESP_READY )
            {
                if ( dht22_get_sensor_data( &dht22, &sens_meas ) == DHT22_OK )
                {
                    dht22_temp = dht22_calculate_temperature( &dht22, sens_meas );
                    dht22_hum = dht22_calculate_humidity( &dht22, sens_meas );

                    log_printf( &logger, " Humidity : %.2f %%\r\n", dht22_hum );
                    log_printf( &logger, " Temperature : %.2f degC\r\n", dht22_temp );
                    log_printf( &logger, " ---------------------------\r\n", dht22_temp );
                    Delay_ms( 1000 );
                }
                
            }
        }
    }
}

void main ( void )
{
    application_init( );

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

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

Additional Support

Resources

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