Ensure healthy air quality by monitoring humidity and temperature with HDC3021 and PIC18LF26K42

Your solution for accurate environmental data

Published Nov 01, 2023

Click board™

Temp&Hum 24 Click

Dev. board

EasyPIC v8

Compiler

NECTO Studio

MCU

PIC18LF26K42

By seamlessly integrating temperature and humidity measurement, this solution enables real-time insights for efficient climate control and environmental management

Hardware Overview

How does it work?

Temp&Hum 24 Click is based on the HDC3021, an integrated interface digital sensor that incorporates both humidity and temperature sensing elements, an analog-to-digital converter, calibration memory, and an I2C compatible interface from Texas Instruments in one package. The sensor performs best when operated within the recommended average temperature and humidity range of 0-50°C and 10-50%RH, with each measurement in a 16-bit format. The HDC3021 also provides excellent measurement accuracy at low power (±0.5%RH and ±0.1°C over a wide operating temperature range). The HDC3021 measures relative humidity through variations in the capacitance of a polymer dielectric. This sensor has a polyimide tape to cover the opening of the humidity sensor element, which protects it from pollutants that can be produced as part of the manufacturing process. The tape must be removed after the final stages of assembly to measure the relative humidity in the ambient environment accurately. To remove the polyimide tape from the humidity sensor element, TI recommends using an ESD-safe tweezer to

grip the adhesive-free tab in the top right corner and slowly peel the adhesive from the top-right corner towards the bottom-left corner in an upward direction. This will help to reduce the risk of scratching the humidity sensor element. Due to contaminants, the natural aging of the sensor's polymer dielectric, and exposure to extreme operating conditions resulting in long-term drift, the HDC3021 accuracy can incur an offset. Thanks to the Offset Error Correction, the RH sensor offset reduces due to aging, exposure to extreme operating conditions, and contaminants to return the sensor to within accuracy specifications. This Click board™ communicates with an MCU using the standard I2C 2-Wire interface to read data and configure settings, supporting Fast Mode Plus up to 1MHz. The HDC3021 also has two measurement modes: Trigger-on-demand and Auto Measurement. Trigger-on Demand is a single temperature and relative humidity measurement reading triggered through an I2C command as needed. After the measurement is converted, the sensor remains in Sleep mode until another I2C command is

received. Auto Measurement mode is a recurring temperature and relative humidity measurement reading, eliminating the need to initiate a measurement request through an I2C command repeatedly. The HDC3021 wakes from Sleep to measurement mode in this mode based on the selected sampling rate. Besides, the HDC3021 allows choosing the least significant bit (LSB) of its I2C slave address using the SMD jumpers labeled ADDR SEL. It also possesses an additional interrupt alert signal, routed on the ALR pin of the mikroBUS™ socket, to provide a notification of ambient temperature and relative humidity measurements that violate programmed thresholds and general reset function routed on the RST pin of the mikroBUS™ socket. 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 for further development.

Temp&Hum 24 Click hardware overview image

Features overview

Development board

EasyPIC v8 is a development board specially designed for the needs of rapid development of embedded applications. It supports many high pin count 8-bit PIC microcontrollers from Microchip, regardless of their number of pins, and a broad set of unique functions, such as the first-ever embedded debugger/programmer. The development board is well organized and designed so that the end-user has all the necessary elements, such as switches, buttons, indicators, connectors, and others, in one place. Thanks to innovative manufacturing technology, EasyPIC v8 provides a fluid and immersive working experience, allowing access anywhere and under any

circumstances at any time. Each part of the EasyPIC v8 development board contains the components necessary for the most efficient operation of the same board. In addition to the advanced integrated CODEGRIP programmer/debugger module, which offers many valuable programming/debugging options and seamless integration with the Mikroe software environment, the board also includes a clean and regulated power supply module for the development board. It can use a wide range of external power sources, including a battery, an external 12V power supply, and a power source via the USB Type-C (USB-C) connector.

Communication options such as USB-UART, USB DEVICE, and CAN are also included, including the well-established mikroBUS™ standard, two display options (graphical and character-based LCD), and several different DIP sockets. These sockets cover a wide range of 8-bit PIC MCUs, from the smallest PIC MCU devices with only eight up to forty pins. EasyPIC v8 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

PIC

MCU Memory (KB)

Silicon Vendor

Microchip

Pin count

RAM (Bytes)

4096

Used MCU Pins

mikroBUS™ mapper

Reset

RA0

RST

SCK

MISO

MOSI

Power Supply

3.3V

Ground

GND

PWM

Alert Interrupt

RB1

INT

I2C Clock

RC3

SCL

I2C Data

RC4

SDA

Power Supply

Ground

GND

Take a closer look

Click board™ Schematic

Step by step

Project assembly

EasyPIC v8 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the EasyPIC v8 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

EasyPIC v8 Access DIPMB 1 - upright/background hardware assembly

NECTO Compiler Selection Step Image hardware assembly

Necto DIP image step 7 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 Temp&Hum 24 Click driver.

Key functions:

temphum24_read_temp_and_rh - This function reads the temperature in celsius and the relative humidity level in percents
temphum24_read_temp_history - This function reads the temperature minimum and maximum values since the beginning of the measurements
temphum24_read_rh_history - This function reads the relative humidity minimum and maximum values since the beginning of measurements

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 TempHum 24 Click example
 *
 * # Description
 * This example demonstrates the use of Temp & Hum 24 Click board by reading
 * the temperature and humidity data.
 * 
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * Initializes the driver and performs the Click default configuration which
 * resets the device and starts the auto measurement mode with data rate of 1 Hz.
 *
 * ## Application Task
 * Reads the temperature (degrees C) and the relative humidity (%RH) data and 
 * displays the results on the USB UART approximately once per second. It also
 * reads and displays the minimum and maximum values measured since the beginning
 * of measurements.
 *
 * @author Stefan Filipovic
 *
 */

#include "board.h"
#include "log.h"
#include "temphum24.h"

static temphum24_t temphum24;
static log_t logger;

void application_init ( void ) 
{
    log_cfg_t log_cfg;  /**< Logger config object. */
    temphum24_cfg_t temphum24_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.
    temphum24_cfg_setup( &temphum24_cfg );
    TEMPHUM24_MAP_MIKROBUS( temphum24_cfg, MIKROBUS_1 );
    if ( I2C_MASTER_ERROR == temphum24_init( &temphum24, &temphum24_cfg ) ) 
    {
        log_error( &logger, " Communication init." );
        for ( ; ; );
    }
    
    if ( TEMPHUM24_ERROR == temphum24_default_cfg ( &temphum24 ) )
    {
        log_error( &logger, " Default configuration." );
        for ( ; ; );
    }
    
    log_info( &logger, " Application Task " );
}

void application_task ( void ) 
{
    float temp = 0, hum = 0;
    if ( TEMPHUM24_OK == temphum24_read_temp_and_rh ( &temphum24, &temp, &hum ) )
    {
        float min_temp = 0, max_temp = 0;
        float min_rh = 0, max_rh = 0;
        log_printf ( &logger, " Temperature: %.2f C\r\n", temp );
        if ( TEMPHUM24_OK == temphum24_read_temp_history ( &temphum24, &min_temp, &max_temp ) )
        {
            log_printf ( &logger, " MIN: %.2f C\r\n MAX: %.2f C\r\n", min_temp, max_temp );
        }
        log_printf ( &logger, "\r\n Humidity: %.1f %%RH\r\n", hum );
        if ( TEMPHUM24_OK == temphum24_read_rh_history ( &temphum24, &min_rh, &max_rh ) )
        {
            log_printf ( &logger, " MIN: %.1f %%RH\r\n MAX: %.1f %%RH\r\n", min_rh, max_rh );
        }
        log_printf ( &logger, "----------------------\r\n" );
        Delay_ms ( 1000 );
    }
}

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