DS3231 is a low-cost, high-precision I2C real-time clock (RTC), with an integrated temperature compensated crystal oscillator (TCXO) and crystal.The device includes a battery input that maintains accurate timing when the main power is turned off. The integrated crystal improves the long-term accuracy of the device and reduces the number of components in the production line. The DS3231 is available in both commercial and industrial temperature ranges and is available in a 16-lead 300-mil SO package. RTCmaintains seconds, minutes, hours, day, date, month, and year information.Months less than 31 days will automatically adjust the end of the month, including leap year correction. The operating format of the clock can be 24 hours or a 12-hour format with / AM / PM indication. Two programmable alarm clocks and a settable square wave output are provided. The address and data are transmitted serially via the I2C bidirectional bus. The precision, temperature-compensated voltage reference and comparator circuit monitors VCC status, detects a power failure, provides a reset output, and automatically switches to a backup power supply if necessary. In addition, the / RST monitor pin can be used as a manual input to generate a μP reset. In addition to high timing accuracy, the DS3231 has several additional features that extend the range of features and options available on the system host. The device integrates a very accurate digital temperature sensor, which can be accessed via the I2C * interface (as in the case of time). The accuracy of the temperature sensor is ± 3 ° C. On-chip control circuitry enables automatic power detection and manages power switching between primary and standby power supplies (ie, low-voltage batteries). If the main power supply fails, the device can continue to provide accurate timing and temperature, performance is not affected. The on-chip reset function can be used to restart the system microprocessor when the main power is reapplied or the voltage value is returned to the allowable range.
   
   

Module parameters:
1. Size: 38mm (length) * 22mm (width) * 14mm (H) 
2. Weight: 8G 
3. To Operating voltage: 3.3--5.5V 
4. The clock chip: high-precision clock chip the DS3231 
5. The clock accuracy: 0 in the range of 40 ℃, the accuracy of 2ppm, the error was about 1 minute 
6. with two calendar alarm 
7. The programmable square-wave output 
8. Real-time clock generator seconds, minutes, hours, day, date, month and year time, and provide valid leap year compensation to 2100 
9. the chip comes with an internal temperature sensor accuracy of 3 deg.] C ± 
10. the memory chip: AT24C32 (storage capacity 32K) 
11.IIC bus interface, the maximum transmission speed of 400KHz (working voltage of 5V) 
12. IIC can cascade other equipment, 24C32 address can / A1 / A2 modified by short circuit A0, for the default address 0x57 
13. a rechargeable battery with LIR2032, to ensure the system after a power failure, the clock then any normal walking 
14. packing: anti-static single packing 
wiring instructions (with Arduino uno r3 as an example):
→ the A5 the SCL 
the SDA → the A4 
the VCC → 5V 
the GND → the GND