The MAXREFDES72 is compatible with Arduino UNO R3, and features a 2 x 6 Digilent Pmod-compatible interface. The MAXREFDES72 Pmod to Arduino interface adapter board consists of the MAX14661 Beyond-the-Rails 16:2 multiplexer, two MAX14611 level shifters, and the DS3231M real-time clock (RTC) with an integrated MEMS resonator. Board communication is configured by writing to the MAX14661 multiplexer over the I2C bus. Eight Arduino digital GPIOs are connected to the Pmod interface through level shifters, and each of these 8 GPIOs connect to the multiplexer. The Pmod interface is offered in a convenient, hand-solderable connector that allows developers with an FPGA development board to mix and match professional-grade peripherals into engineering prototypes.