Intermediate
30 min

Turn moments into opportunities with AB0805 and STM32F091RC

Sync your world with our real-time clock – experience perfect timing!

RTC 20 Click with Nucleo-64 with STM32F091RC MCU

Published Feb 26, 2024

Click board™

RTC 20 Click

Dev Board

Nucleo-64 with STM32F091RC MCU

Compiler

NECTO Studio

MCU

STM32F091RC

Experience the precision of advanced real-time clock technology, ensuring reliable timekeeping and synchronization in your solution

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Hardware Overview

How does it work?

RTC 20 Click is based on the AB0805, a low-power, real-time clock (RTC) time-keeping device from Abracon. The AB0805 is configured to transmit calendar and time data to the MCU based on a 32.768kHz quartz crystal and comes with 256 bytes of general-purpose RAM. It reads and writes clock/calendar data from and to the MCU in units ranging from seconds to the last two digits of the calendar year, providing seconds, minutes, hours, dates, days, weeks, months, years, and century information. The end-of-the-month date is automatically adjusted for months with fewer than 31 days, including corrections for the leap year until 2199. This Click board™

communicates with the MCU using the standard I2C 2-Wire interface to read data and configure settings, supporting a Fast Mode operation up to 400kHz. By utilizing an automatic backup switch feature, this RTC can use an external power source (220mF supercapacitor) when there is no power supply on its main power terminals, thus allowing for uninterrupted operation. Besides an automatic backup switchover circuit, the AB0805 has flexible inputs that aggregate various interrupt sources to an MCU. Based on this, functions like external interrupt or watchdog timer reset could be found on this Click board™ routed on the EXT and WDI pins of the mikroBUS™ socket, as well as the

primary and secondary interrupt signals routed on the IR1 and IR2 pins of the mikroBUS™ socket. In addition to the alarm/interrupt feature, the IR1 signal also provides the selectable-frequency square wave signal (512Hz default value). 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.

RTC 20 Click top side image
RTC 20 Click bottom side image

Features overview

Development board

Nucleo-64 with STM32F091RC MCU offers a cost-effective and adaptable platform for developers to explore new ideas and prototype their designs. This board harnesses the versatility of the STM32 microcontroller, enabling users to select the optimal balance of performance and power consumption for their projects. It accommodates the STM32 microcontroller in the LQFP64 package and includes essential components such as a user LED, which doubles as an ARDUINO® signal, alongside user and reset push-buttons, and a 32.768kHz crystal oscillator for precise timing operations. Designed with expansion and flexibility in mind, the Nucleo-64 board features an ARDUINO® Uno V3 expansion connector and ST morpho extension pin

headers, granting complete access to the STM32's I/Os for comprehensive project integration. Power supply options are adaptable, supporting ST-LINK USB VBUS or external power sources, ensuring adaptability in various development environments. The board also has an on-board ST-LINK debugger/programmer with USB re-enumeration capability, simplifying the programming and debugging process. Moreover, the board is designed to simplify advanced development with its external SMPS for efficient Vcore logic supply, support for USB Device full speed or USB SNK/UFP full speed, and built-in cryptographic features, enhancing both the power efficiency and security of projects. Additional connectivity is

provided through dedicated connectors for external SMPS experimentation, a USB connector for the ST-LINK, and a MIPI® debug connector, expanding the possibilities for hardware interfacing and experimentation. Developers will find extensive support through comprehensive free software libraries and examples, courtesy of the STM32Cube MCU Package. This, combined with compatibility with a wide array of Integrated Development Environments (IDEs), including IAR Embedded Workbench®, MDK-ARM, and STM32CubeIDE, ensures a smooth and efficient development experience, allowing users to fully leverage the capabilities of the Nucleo-64 board in their projects.

Nucleo 64 with STM32F091RC MCU double side image

Microcontroller Overview

MCU Card / MCU

default

Architecture

ARM Cortex-M0

MCU Memory (KB)

256

Silicon Vendor

STMicroelectronics

Pin count

64

RAM (Bytes)

32768

You complete me!

Accessories

Click Shield for Nucleo-64 comes equipped with two proprietary mikroBUS™ sockets, allowing all the Click board™ devices to be interfaced with the STM32 Nucleo-64 board with no effort. This way, Mikroe allows its users to add any functionality from our ever-growing range of Click boards™, such as WiFi, GSM, GPS, Bluetooth, ZigBee, environmental sensors, LEDs, speech recognition, motor control, movement sensors, and many more. More than 1537 Click boards™, which can be stacked and integrated, are at your disposal. The STM32 Nucleo-64 boards are based on the microcontrollers in 64-pin packages, a 32-bit MCU with an ARM Cortex M4 processor operating at 84MHz, 512Kb Flash, and 96KB SRAM, divided into two regions where the top section represents the ST-Link/V2 debugger and programmer while the bottom section of the board is an actual development board. These boards are controlled and powered conveniently through a USB connection to program and efficiently debug the Nucleo-64 board out of the box, with an additional USB cable connected to the USB mini port on the board. Most of the STM32 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 STM32 Nucleo-64 board with our Click Shield for Nucleo-64, you can access hundreds of Click boards™, working with 3.3V or 5V logic voltage levels.

Click Shield for Nucleo-64 accessories 1 image

Used MCU Pins

mikroBUS™ mapper

Secondary Interrupt
PC0
AN
Watchdog Timer Reset
PC12
RST
NC
NC
CS
NC
NC
SCK
NC
NC
MISO
NC
NC
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
External Interrupt
PC8
PWM
Primary Interrupt
PC14
INT
NC
NC
TX
NC
NC
RX
I2C Clock
PB8
SCL
I2C Data
PB9
SDA
NC
NC
5V
Ground
GND
GND
1

Take a closer look

Click board™ Schematic

RTC 20 Click Schematic schematic

Step by step

Project assembly

Click Shield for Nucleo-64 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the Nucleo-64 with STM32F091RC MCU as your development board.

Click Shield for Nucleo-64 front image hardware assembly
Nucleo 64 with STM32F401RE MCU front image hardware assembly
EEPROM 13 Click front image hardware assembly
Prog-cut hardware assembly
Nucleo-64 with STM32XXX MCU MB 1 Mini B Conn - 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
Clicker 4 for STM32F4 HA 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 via Debug Mode

1. Once the code example is loaded, pressing the "DEBUG" button initiates the build process, programs it on the created setup, and enters Debug mode.

2. After the programming is completed, a header with buttons for various actions within the IDE becomes visible. Clicking the green "PLAY" button starts reading the results achieved with the Click board™. The achieved results are displayed in the Application Output tab.

DEBUG_Application_Output

Software Support

Library Description

This library contains API for RTC 20 Click driver.

Key functions:

  • rtc20_set_time - RTC 20 set time function.

  • rtc20_set_date - RTC 20 set date function.

  • rtc20_get_time - RTC 20 get time function.

Open Source

Code example

This example can be found in NECTO Studio. Feel free to download the code, or you can copy the code below.

/*!
 * @file main.c
 * @brief RTC 20 Click example
 *
 * # Description
 * This example demonstrates the use of the RTC 20 click board™
 * by reading and displaying the RTC time and date values.
 *
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * Initialization of I2C module, log UART and additional pins.
 * After driver initialization the app set RTC time to 23:59:50
 * and set date to Tuesday 28.02.2023.
 *
 * ## Application Task
 * This is an example that shows the use of a RTC 20 Click board™.
 * In this example, we read and display the current time ( PM ) 
 * and date ( day of the week ), which we also previously set.
 * Results are being sent to the Usart Terminal where you can track their changes.
 * All data logs write on USB changes every 1 sec.
 *
 *
 * @author Nenad Filipovic
 *
 */

#include "board.h"
#include "log.h"
#include "rtc20.h"

static rtc20_t rtc20;
static log_t logger;
static uint8_t new_sec = 255;
static rtc20_time_t time;
static rtc20_date_t date;

/**
 * @brief RTC 20 display day of week name function.
 * @details This function display the name of day of the week.
 */
static void display_day_of_week ( void );

void application_init ( void ) 
{
    log_cfg_t log_cfg;  /**< Logger config object. */
    rtc20_cfg_t rtc20_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.
    rtc20_cfg_setup( &rtc20_cfg );
    RTC20_MAP_MIKROBUS( rtc20_cfg, MIKROBUS_1 );
    if ( I2C_MASTER_ERROR == rtc20_init( &rtc20, &rtc20_cfg ) ) 
    {
        log_error( &logger, " Communication init." );
        for ( ; ; );
    }

    time.hour   = 23;
    time.minute = 59;
    time.second = 50;
    if ( RTC20_OK == rtc20_set_time( &rtc20, time ) )
    {
        log_printf( &logger, "  Set time : %.2d:%.2d:%.2d\r\n", 
                    ( uint16_t ) time.hour, ( uint16_t ) time.minute, ( uint16_t ) time.second );
    }

    date.day_of_week = RTC20_DW_TUESDAY;
    date.day         = 28;
    date.month       = 2;
    date.year        = 23;
    if ( RTC20_OK == rtc20_set_date( &rtc20, date ) )
    {
        log_printf( &logger, "  Set date : %.2d-%.2d-%.2d\r\n", 
                    ( uint16_t ) date.day, ( uint16_t ) date.month, ( uint16_t ) date.year );
    }

    Delay_ms( 1000 );
    log_printf( &logger, "---------------------\r\n" );
}

void application_task ( void ) 
{
    if ( RTC20_OK == rtc20_get_time( &rtc20, &time ) )
    {
        if ( RTC20_OK == rtc20_get_date( &rtc20, &date ) )
        {
            if ( time.second != new_sec )
            {
                log_printf( &logger, "  Date : %.2d-%.2d-%.2d\r\n", 
                            ( uint16_t ) date.day, ( uint16_t ) date.month, ( uint16_t ) date.year );
                display_day_of_week( );
                log_printf( &logger, "  Time : %.2d:%.2d:%.2d\r\n", 
                            ( uint16_t ) time.hour, ( uint16_t ) time.minute, ( uint16_t ) time.second );
                log_printf( &logger, "- - - - - - - - - - -\r\n" );
                new_sec = time.second;
                Delay_ms( 1 );
            }
        }
    }
    Delay_ms( 1 );
}

void main ( void ) 
{
    application_init( );

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

static void display_day_of_week ( void ) 
{
    switch ( date.day_of_week ) 
    {
        case RTC20_DW_SUNDAY: 
        {
            log_printf( &logger, "Sunday\r\n" );
            break;
        }
        case RTC20_DW_MONDAY: 
        {
            log_printf( &logger, "Monday\r\n" );
            break;
        }
        case RTC20_DW_TUESDAY: 
        {
            log_printf( &logger, "Tuesday\r\n" );
            break;
        }
        case RTC20_DW_WEDNESDAY: 
        {
            log_printf( &logger, "Wednesday\r\n" );
            break;
        }
        case RTC20_DW_THURSDAY: 
        {
            log_printf( &logger, "Thursday\r\n" );
            break;
        }
        case RTC20_DW_FRIDAY: 
        {
            log_printf( &logger, "Friday\r\n" );
            break;
        }
        case RTC20_DW_SATURDAY: 
        {
            log_printf( &logger, "Saturday\r\n" );
            break;
        }
        default:
        {
            log_printf( &logger, "Unknown\r\n" );
        }
    }
}

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

Additional Support

Resources

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