RTC - DS3231 + EEPROM AT24C32 I2C Precision Module with Battery

DS3231 AT24C32 I²C Precision RTC Module (with CR2032 Slot)

A highly accurate and convenient real-time clock (RTC) module featuring a DS3231 chip and 32 KB EEPROM (AT24C32), complete with a coin-cell battery holder to maintain timekeeping when external power is removed. Ideal for microcontroller projects, data loggers, and embedded applications.

Key Features & Specs

• Main RTC Chip: DS3231M/SN — temperature-compensated crystal oscillator (TCXO) ensures ±2 ppm accuracy from 0 °C to +40 °C (up to ±3.5 ppm in full range) 
• EEPROM: AT24C32, providing 32 KB (4096 bytes) non-volatile storage
• Operating Voltage: 2.7–5.5 V (commonly used at 3.3 V or 5 V)
• Backup Supply: CR2032 coin-cell battery (battery included)
• Interface: I²C, with addresses 0x68 (RTC) and 0x57 (EEPROM); supports up to 400 kHz bus speed
• Time Calendar: Years, months, days, hours, minutes, seconds, leap-year correction through 2100
• Alarms: Two programmable time-of-day alarms, plus square-wave / interrupt output (SQW/INT)
• Temperature Sensor: Integrated thermometer with ±3 °C accuracy, accessible over I²C

Physical Specs

• Dimensions: 38 × 22 × 14 mm
• Weight: Approx. 8 g

Power & Ports

• Primary Power: VCC (2.7–5.5 V), GND
• I²C Lines: SDA, SCL
• Backup: VBAT pin connects to CR2032 for uninterrupted timekeeping
• Extra Pins: SQW/INT (square-wave or alarm signal), 32 kHz output, RST available on some modules

Performance & Reliability

• Time Accuracy: ±2 ppm at room temperature (~1 min/year); ±3.5 ppm across full range
• Temperature Range: –40 °C to +85 °C
• Power Fail & VBAT: Automatically switches to battery backup when VCC drops ﹣ ensures seamless time retention

Typical Use Cases

• Timestamping events in data loggers, such as sensor recordings
• Scheduling actions — alarms, wake-up signals via SQW/INT
• Maintaining accurate time for clocks, calendars, and IoT systems
• Storage of calibration settings, configurations, or small logs in onboard EEPROM

Spec Summary:

• RTC chip: DS3231 (TCXO, ±2 ppm, integrated temp sensor)
• EEPROM: AT24C32, 32 KB storage
• Voltage: 2.7–5.5 V (works at 3.3 V / 5 V)
• Interfaces: I²C (0x68 for RTC, 0x57 for EEPROM) at up to 400 kHz
• Backup: CR2032 coin cell, battery slot included
• Alarms: 2 time-of-day alarms, square-wave output
• Temperature range: –40 °C to +85 °C
• Size & weight: 38 × 22 × 14 mm; ~8 g