This application report describes the hardware and software interface between the Texas Instruments MSP430F413 16-bit micro-controller and TMP100 digital temperature sensor, implementing an ultra-low power temperature measurement system (Figure 1) capable of operation from a single 3-V battery for over 10 years. The following sections demonstrate how to interface the two devices in hardware as well as implementation of the communication protocol via a two-wire I2C bus in software. While demonstrated here specifically for the TMP100, the software interface described can be applied to any MSP430 micro-controller and I2C-compatible slave peripheral device.