SainSmart SX105 Multifunction Expansion Board for Raspberry Pi B+ Input Voltage 6V to 23Vdc converted to 5V, 3A via step-down DC/DC converter to power the Raspberry Pi USB Storage Self-powered USB hub with 3 ports Communication Control the Raspberry Pi over RS232 or connect to external serial accessories Real-time clock (RTC) Based on DS3231SN with included CR2032 battery Reader/Writer Supports microSD / microSDHC / microSDXC Convenient to write OS image