SwitchDoc Labs DS3231, AT24C32 EPROM, Battery and Software Includes Open Source Software for DS3231 and AT24C32 for Arduino and Raspberry Pi A low-cost, accurate I2C real-time clock module with an temperature-compensated crystal oscillator (TCXO) improving long-term accuracy. Includes 32K bits of non-volatile memory organzied as 4K by 8bit memory. Includes software. Clock accuracy is 2 ppm and error is about 1 minute per year. See benchmark on switchdoc.com Includes Battery Backup