Adafruit’s got a handy breakout board for the DS1307 RTC available. This chip isn’t nearly as accurate as the DS3231 used in the Chronodot but it’s quite a bit cheaper. The breakout makes ...

only implementation of a synchronization core allowing to read and write a I2C Realtime Clock (RTC) like the DS1307 or MCP7941x. Access to the RTC is done from the FPGA without software interaction.

DS1307 modules are readily available, and often the cheapest RTC solution available at most ... The RV-1805 draws so little power that this Sparkfun module gets by without a backup battery at ...