The USB-RTC is a simple real-time clock that can supply devices without one (e.g. Raspberry Pi) with the current time and date via USB. The CR1220 or CR1225 backup battery keeps the clock running even without an external power supply. The built-in 32.768 kHz crystal ensures a reasonable accuracy of the clock. The on board CH330N (or CH340N) USB-to-serial adapter can also be used as a UPDI programmer, so that no external programming device is required. This makes the USB-RTC also suitable as a development board for RTC applications based on the new tinyAVR or megaAVR microcontrollers.