RTC 9 Click is a real-time clock module that has an extremely low power consumption, allowing it to be used with a single button cell battery, for an extended period of time. This board features the M41T82, real-time clock (RTC) with battery switchover, from ST Microelectronics. It features factory-calibrated accuracy of ±5 ppm typically, automatic switchover and reset output circuitry, programmable alarm with interrupt function, and more. All these features make RTC 9 Click excellent choice for manufacturers for applications such as portable applications, logging devices, wearables, medical equipment, and similar.

RTC 9 Click is supported by a mikroSDK compliant library, which includes functions that simplify software development.

RTC 9 click is based on the M41T82, an extreme low power real-time clock/calendar (RTC) module from ST Microelectronics. Thanks to its high integration level, this module provides high time accuracy, factory calibrated to ±5 ppm even after two reflows, with a very low count of external components required. It has a full RTC function, offering programmable counters, alarms, and an interrupt engine with selectable event reporting sources. The operational parameters are stored within the internal user SRAM memory, which is battery-backed, thus allowing their persistence in the event of the complete power failure.

M41T82 features a built-in 32.768 kHz oscillator. However, RTC 9 Click has an external oscillator too, in order to achieve the best accuracy possible. Eight bytes of the register map are used for the clock/calendar function and are configured in binary-coded decimal (BCD) format. An additional 17 bytes of the register map provide status/control of the two alarms, watchdog, 8-bit counter, and square wave functions. An additional seven bytes are made available as user SRAM. M41T82 supports the I2C communication interface, which is also used on the RTC 9 Click for communicating with the main microcontroller through the mikroBUS socket.

Functions available to the user include a non-volatile, time-of-day clock/calendar, two alarm interrupts, watchdog timer, programmable 8-bit counter, and square wave outputs. The eight clock address locations contain the century, year, month, date, day, hour, minute, second, and tenths/hundredths of a second in 24-hour BCD format. Corrections for 28, 29 (leap year), 30, and 31 day months are made automatically.

This Click board™ is designed to be operated with both 3.3V and 5V logic levels that can be selected via VCC SEL jumper. This allows for both 3.3V and 5V capable MCUs to use the I2C communication lines properly.

• Interface: I²C
• Compatibility: mikroBUS™
• Dimensions: 42.9 x 25.4mm
• Input Voltage: 3.3V or 5V
• Supply Voltage (for R version): Min. 2.7V, Typ. 3.3V, Max. 5.5V
• Supply Current: 365nA
• Accuracy: 5ppm
• Operating Temperature Range: Min. -40°C, Max. +85°C

• Schematic
• M41T82 Datasheet
• mikroSDK
• GitHub