pin_io_ds3231.txt

[GND] <-- GND
[Vin] <-- [3.3V same power source as for Arduino]
[BAT] <-- [direct positive voltage from LiPo battery. Can handel between 2.3V and 5.5V]

[DS3231][i2c SCL](logic high level is Vin) <--> [arduino][PC5](i2c SCL)
[DS3231][i2c SDA](logic high level is Vin) <--> [arduino][PC4](i2c SDA)


[DS3231][32K]	[not connected]
[DS3231][SQW]	[not connected]
[DS3231][RST]	[not connected]