RTC 16 Click is a compact add-on board that accurately keeps the time of a day. This board features the BU9873, a CMOS real-time clock that has a built-in interrupt generation function from Rohm Semiconductors. The BU9873 provides year, month, day, weekday, hours, minutes, and seconds based on a 32.768kHz quartz crystal. This RTC is connected to the MCU through an I2C interface and configured to serial transmit time and calendar data. 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 16 Click is supported by a mikroSDK compliant library, which includes functions that simplify software development.

RTC 16 Click as its foundation uses the BU9873, an I2C configurable real-time clock/calendar optimized for low power operations from Rohm Semiconductors. The BU9873 is configured to perform the serial transmission of calendar and time data to the MCU and comes with an integrated interrupt generation function. It also contains a built-in high-precision oscillation adjustment circuit which enables the adjustment of time counts with a digital method and correct deviations in the oscillation frequency of the crystal oscillator. This RTC is also characterized by an automatic leap year recognition until the future 2099 year.

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. An alarm and interrupt function is also available that outputs an interrupt signal to the INT pin of the mikroBUS™ socket when the day of the week, hour, or minute matches with the preset time. An alarm may be selectable between ON and OFF for each day of the week, allowing outputting warning every day or on a specific day indicated by a red LED marked as ALARM. Besides, the RTC 16 Click also has an onboard header labeled CLKOUT, 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 16 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 CLKOUT: 32 kHz
• Operating Temperature Range: Min. -40°C, Typ. +25°C, Max. +85°C

• Schematic
• BU9873 Datasheet
• mikroSDK
• LibStock