Ensure accurate timekeeping with AM1805AQ and PIC18F57Q43
Ultra-low power real-time clock solution with I2C interface
Published Mar 19, 2025
Click board™
RTC 22 Click
Dev. board
Curiosity Nano with PIC18F57Q43
Compiler
NECTO Studio
MCU
PIC18F57Q43
Provide precise timekeeping for applications that need to track time accurately, such as data logging or scheduling tasks
A
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Hardware Overview
How does it work?
RTC 22 Click is based on the AM1805AQ, an ultra-low-power real-time clock with integrated power management from Ambiq. Using Ambiq’s proprietary SPOT® (Subthreshold Power Optimized Technology) CMOS platform, this RTC sets a new industry standard with power consumption as low as 14nA, making it an ideal solution for power-sensitive applications. The AM1805AQ incorporates on-chip oscillators to ensure minimal power usage while providing full RTC functionality, including battery backup, programmable timers, counters, and alarms, along with an I2C interface for communication with a host MCU. Its integrated power switch and intelligent system sleep manager enable precise control over power states, allowing the RTC to be a supervisory component in MCU-based systems such as medical devices, utility meters, data loggers, household appliances, consumer electronics, and communication equipment. The AM1805AQ’s functionality is divided into baseline timekeeping, advanced timekeeping, and power management. Baseline timekeeping uses a 32.768kHz crystal oscillator, offering maximum frequency accuracy with an ultra-low current draw of just 55nA. Its digital calibration algorithm ensures frequency tuning accuracy down to 2ppm at specific temperatures. Advanced timekeeping introduces additional oscillation modes, including an RC oscillator and an auto-calibration mode, along with a finite state machine that manages host MCU transitions between active and low-power states. The integrated power switch, with an impedance of approximately 1Ω, can cut off ground current to the host MCU, reducing sleep current to below 1nA, making RTC 22 Click an essential component for any low-power embedded system. RTC 22 Click is powered from the 3.3V
mikroBUS™ power rail but also supports standalone operation, thanks to the PWY0150S micro-energy storage device from ITEN. This highly integrated, high-power-density battery delivers up to 20mA of current with a capacity of 150µAh in a compact SMD QFN package. Designed for high performance, it supports fast charging and can endure up to 1000 cycles at 100% depth of discharge (DoD). PWY0150S’s contribution to the design ensures reliable and efficient energy storage, enabling RTC 22 Click to maintain functionality even in low-power scenarios. The battery is recharged by the onboard XC6240 series charging IC for rechargeable batteries, providing a stable 2.7V charging voltage after battery depletion. Battery power can be enabled via the VBAT switch by toggling it from OFF to ON. Transitioning to standalone operation allows for significant power savings by cutting specific traces on the back of the board, which disables the lower part of the board below the RESET button, including the power indicator and ClickID circuitry. In this low-power mode, the timer interrupt signal can be used on the IRQ pin by connecting the right-side LP CUT trace on the back of the board, whereas in normal operation, this pin is reserved for ClickID communication. This Click board™ communicates with the host MCU via an I2C interface, supporting clock frequencies up to 400kHz to ensure fast and reliable data exchange. Alongside the standard I2C pins, the board includes an INT pin, an open-drain interrupt output, that signals when the RTC is ready to be accessed through the serial interface. Additionally, the WDI pin serves as a watchdog timer reset signal, safeguarding against system failures by resetting the host MCU if it becomes unresponsive, thus ensuring continuous operation.
This pin can also function as an external interrupt input, offering further flexibility for triggering specific events within the system. RTC 22 Click also features a group of unsoldered pins that provide additional functionality and flexibility. On the left side of the board, the RSTO pin serves as an open-drain reset output signal from the main AM1805AQ IC, used to reset the host MCU or other connected devices when triggered by internal RTC events, ensuring proper system initialization and recovery. Alongside it, the EXTRST pin functions as an external reset input, allowing the host MCU or external sources to reset the RTC itself when necessary. This same reset functionality is also accessible via the onboard RESET button, offering a manual alternative for triggering a system reset. On the right side, three unsoldered pins offer further capabilities: PSW acts as a power switch output for controlling external devices (also available as PSW pin on mikroBUS™ socket), turning their power supply ON or OFF; CLK provides a square-wave clock output that can serve as a precise timing reference for the host MCU or other peripherals; and EXTI functions as an external interrupt input, allowing external signals to trigger interrupts within the RTC, facilitating event-driven operations and synchronized timing in complex embedded systems. 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. It also comes equipped with a library containing functions and example code that can be used as a reference for further development.
Features overview
Development board
PIC18F57Q43 Curiosity Nano evaluation kit is a cutting-edge hardware platform designed to evaluate microcontrollers within the PIC18-Q43 family. Central to its design is the inclusion of the powerful PIC18F57Q43 microcontroller (MCU), offering advanced functionalities and robust performance. Key features of this evaluation kit include a yellow user LED and a responsive
mechanical user switch, providing seamless interaction and testing. The provision for a 32.768kHz crystal footprint ensures precision timing capabilities. With an onboard debugger boasting a green power and status LED, programming and debugging become intuitive and efficient. Further enhancing its utility is the Virtual serial port (CDC) and a debug GPIO channel (DGI
GPIO), offering extensive connectivity options. Powered via USB, this kit boasts an adjustable target voltage feature facilitated by the MIC5353 LDO regulator, ensuring stable operation with an output voltage ranging from 1.8V to 5.1V, with a maximum output current of 500mA, subject to ambient temperature and voltage constraints.
Microcontroller Overview
MCU Card / MCU
Architecture
PIC
MCU Memory (KB)
128
Silicon Vendor
Microchip
Pin count
48
RAM (Bytes)
8196
You complete me!
Accessories
Curiosity Nano Base for Click boards is a versatile hardware extension platform created to streamline the integration between Curiosity Nano kits and extension boards, tailored explicitly for the mikroBUS™-standardized Click boards and Xplained Pro extension boards. This innovative base board (shield) offers seamless connectivity and expansion possibilities, simplifying experimentation and development. Key features include USB power compatibility from the Curiosity Nano kit, alongside an alternative external power input option for enhanced flexibility. The onboard Li-Ion/LiPo charger and management circuit ensure smooth operation for battery-powered applications, simplifying usage and management. Moreover, the base incorporates a fixed 3.3V PSU dedicated to target and mikroBUS™ power rails, alongside a fixed 5.0V boost converter catering to 5V power rails of mikroBUS™ sockets, providing stable power delivery for various connected devices.
Used MCU Pins
mikroBUS™ mapper
Take a closer look
Click board™ Schematic
Step by step
Project assembly
Start by selecting your development board and Click board™. Begin with the Curiosity Nano with PIC18F57Q43 as your development board.
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
RTC 22 Click demo application is developed using the NECTO Studio, ensuring compatibility with mikroSDK's open-source libraries and tools. Designed for plug-and-play implementation and testing, the demo is fully compatible with all development, starter, and mikromedia boards featuring a mikroBUS™ socket.
Example Description
This example demonstrates the use of RTC 22 Click by reading and displaying the time and date values.
Key functions:
rtc22_cfg_setup- Config Object Initialization function.rtc22_init- Initialization function.rtc22_set_time- This function sets the starting time values - second 100th, second, minute and hour.rtc22_read_time- This function reads the current time values - second 100th, second, minute and hour.rtc22_set_date- This function sets the starting date values - day of week, day, month and year.
Application Init
Initializes the driver, checks the communication, and sets the starting time and date.
Application Task
Reads and displays on the USB UART the current time and date values once per second.
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 RTC 22 Click example
*
* # Description
* This example demonstrates the use of RTC 22 Click board by reading and displaying
* the time and date values.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Initializes the driver, checks the communication, and sets the starting time and date.
*
* ## Application Task
* Reads and displays on the USB UART the current time and date values once per second.
*
* @author Stefan Filipovic
*
*/
#include "board.h"
#include "log.h"
#include "rtc22.h"
static rtc22_t rtc22;
static log_t logger;
static rtc22_time_t time;
static rtc22_date_t date;
/**
* @brief RTC 22 get day of week name function.
* @details This function returns the name of day of the week as a string.
* @param[in] ctx : Click context object.
* See #rtc22_t object definition for detailed explanation.
* @param[in] day_of_week : Day of week decimal value.
* @return Name of day as a string.
* @note None.
*/
static uint8_t *rtc22_get_day_of_week_name ( uint8_t day_of_week );
void application_init ( void )
{
log_cfg_t log_cfg; /**< Logger config object. */
rtc22_cfg_t rtc22_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.
rtc22_cfg_setup( &rtc22_cfg );
RTC22_MAP_MIKROBUS( rtc22_cfg, MIKROBUS_1 );
if ( I2C_MASTER_ERROR == rtc22_init( &rtc22, &rtc22_cfg ) )
{
log_error( &logger, " Communication init." );
for ( ; ; );
}
if ( RTC22_ERROR == rtc22_check_communication ( &rtc22 ) )
{
log_error( &logger, " Check communication." );
for ( ; ; );
}
time.hour = 23;
time.minute = 59;
time.second = 50;
time.second_100th = 0;
if ( RTC22_OK == rtc22_set_time ( &rtc22, &time ) )
{
log_printf( &logger, " Set time: %.2u:%.2u:%.2u\r\n",
( uint16_t ) time.hour, ( uint16_t ) time.minute, ( uint16_t ) time.second );
}
date.day_of_week = RTC22_TUESDAY;
date.day = 31;
date.month = 12;
date.year = 24;
if ( RTC22_OK == rtc22_set_date ( &rtc22, &date ) )
{
log_printf( &logger, " Set date: %s, %.2u.%.2u.20%.2u.\r\n",
rtc22_get_day_of_week_name ( date.day_of_week ),
( uint16_t ) date.day, ( uint16_t ) date.month, ( uint16_t ) date.year );
}
Delay_ms ( 100 );
log_info( &logger, " Application Task " );
}
void application_task ( void )
{
if ( RTC22_OK == rtc22_read_time ( &rtc22, &time ) )
{
log_printf( &logger, " Time: %.2u:%.2u:%.2u\r\n",
( uint16_t ) time.hour, ( uint16_t ) time.minute, ( uint16_t ) time.second );
}
if ( RTC22_OK == rtc22_read_date ( &rtc22, &date ) )
{
log_printf( &logger, " Date: %s, %.2u.%.2u.20%.2u.\r\n",
rtc22_get_day_of_week_name ( date.day_of_week ),
( uint16_t ) date.day, ( uint16_t ) date.month, ( uint16_t ) date.year );
}
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;
}
static uint8_t *rtc22_get_day_of_week_name ( uint8_t day_of_week )
{
switch ( day_of_week )
{
case RTC22_MONDAY:
{
return "Monday";
}
case RTC22_TUESDAY:
{
return "Tuesday";
}
case RTC22_WEDNESDAY:
{
return "Wednesday";
}
case RTC22_THURSDAY:
{
return "Thursday";
}
case RTC22_FRIDAY:
{
return "Friday";
}
case RTC22_SATURDAY:
{
return "Saturday";
}
case RTC22_SUNDAY:
{
return "Sunday";
}
default:
{
return "Unknown";
}
}
}
// ------------------------------------------------------------------------ END
Additional Support
Resources
Category:RTC
