Evaluation of Power Efficiency for Digital Serial Interfaces of Microcontrollers

Over the recent years, novel low-power microcontrollers have been introduced. This has allowed the development of various applications, which can operate over long periods of time and fulfill their tasks having very limited amount of energy, such as e.g., Wireless Sensor Networks (WSN).Nonetheless, for fulfilling their tasks such devices in addition to the central processor often have to include several microcontrollers or some peripherals, such as sensors, external memory chips or other application-specific hardware. All those peripherals, except the energy for actual operation also require some energy for communicating to the central processor. In the paper we are investigating and comparing the energy consumption for three most widely used embedded systems' digital serial interfaces, namely I2C, SPI and UART. The presented results have been obtained using the real-life microcontroller (PIC18F family from Microchip) and reveal the energy consumption for different interface implementation methods (hardware vs. software) and various scenarios (idle interface, different data transmit or receive scenarios). The presented data can be valuable as well for researchers and engineers and allow to choose the most energy efficient communication interface and its implementation method to be used in the most energy-critical applications.