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Real Time Clocks

The DS3231 is a highly accurate real-time clock (RTC) integrated circuit that maintains precise time using an internal temperature-compensated crystal oscillator (TCXO). The letters "DS" initially were for Dallas Semiconductor, the name of the company that originally created the chip.

Key features:

  • Accuracy within ±2ppm (about 1 minute/year) across -40°C to +85°C
  • Battery backup using CR2032 for continuous timekeeping
  • I2C interface operating at 400kHz
  • Built-in temperature sensor (±3°C accuracy)
  • Two programmable time-of-day alarms

The device stores time data in BCD format across multiple registers:

0x00: Seconds 0x01: Minutes 0x02: Hours 0x03: Day 0x04: Date 0x05: Month 0x06: Year

Example: Reading hour register 0x02 returns value 0x15 in BCD, representing 15:00 (3:00 PM).

Driver

We will be using the

How Long Will The Battery Last

The typical operational duration of the backup coin-cell battery in real-time clock circuits ranges from 2 to 10 years, depending on temperature conditions and current draw.

The DS3231 RTC module used in our kits draw 3μA at room temperature typically operates for 8 years on a single CR2032 battery. The key factors affecting battery life are:

  • Operating temperature (lower temps extend life)
  • Current draw of the RTC (varies by model)
  • Battery capacity (typical CR2032 = 220mAh)
  • Additional features active (temperature sensing, alarms, etc.)

References

DS3231 Data Sheet on the Analog Devices Website - note that Analog Devices acquired Dallas Semiconductor.