RTC 17 Click is a compact add-on board that accurately keeps the time of a day. This board features the RV5C387A, a CMOS real-time clock with a built-in interrupt generation function from Nisshinbo Micro Devices Inc, to perform serial transmission of time and calendar data to the MCU. The BU9873 provides information like year, month, day, weekday, hours, minutes, and seconds based on a 32.768kHz quartz crystal through an I2C serial interface to transmit time and calendar data to the MCU. It also has an alarm function that outputs an interrupt signal to the MCU when the day of the week, hour, or minute matches with the preset time. This Click board™ is suitable for various time-keeping applications, including daily alarms, metering applications, and others requiring an accurate RTC for their operation.

RTC 17 Click is supported by a mikroSDK compliant library, which includes functions that simplify software development.

RTC 17 Click as its foundation uses the RV5C387A, an I2C configurable real-time clock/calendar optimized for low power operations from Nisshinbo Micro Devices Inc. The RV5C387A is configured to transmit calendar and time data to the MCU and comes with an integrated interrupt generation function. It reads and writes time data from and to the MCU in units ranging from seconds to the last two digits of the calendar year. The calendar year will automatically be identified as a leap year when its last two digits are a multiple of 4. Consequently, leap years up to the year 2099 can automatically be recognized.

This Click board™ communicates with MCU using the standard I2C 2-Wire interface to read data and configure settings, supporting a Fast Mode operation up to 400kHz. It also incorporates an alarm circuit configured to generate an interrupt signal to the INT pin of the mikroBUS™ socket from its A, B, or C interrupt pin at preset times. The alarm circuit allows two types of alarm settings specified by the Alarm_W registers and the Alarm_D registers.

The Alarm_W registers (interrupt B) allow a week, hour, and minute alarm settings, including combinations of multiple day-of-week settings such as Monday, Wednesday, while the Alarm_D registers (interrupt C) allow an hour and minute alarm settings. Besides, the RV5C387A can generate periodic interrupt signals aside from interrupt signals generated by the alarm circuit from interrupt A pin. The RTC 17 Click also has an onboard header labeled CLKO, which provides clock pulses of 32kHz.

The most common RTC configuration, like this one, is a battery-backed up, which maintains time and continues its work without interruption in the event of a power failure. That’s why, in addition to the BU9873, the RTC 17 Click is equipped with a button cell battery holder compatible with the 3000TR battery holder, suitable for 12mm Coin Cell batteries.

This Click board™ can operate with both 3.3V and 5V logic voltage levels selected via the VCC 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 that contains easy-to-use functions and an example code that can be used, as a reference, for further development.

• Interface: I²C
• Compatibility: mikroBUS™
• Dimensions: 42.9 x 25.4mm
• Input Voltage: 3.3V or 5V
• Clock Output CLKO: 32 kHz
• Operating Temperature Range: Min. -40°C, Typ. +25°C, Max. +85°C

• Schematic
• RV5C387A Datasheet
• mikroSDK
• GitHub