FRAMEWORK IMPLEMENTATION, FIRMWARE DEVELOPMENT AND CHARACTERIZATION OF FLEX-SPI COMMUNICATION PROTOCOL: ENERGY CONSUMPTION ANALYSIS AND COMPARISON WITH I2C STANDARD

In this paper, we report a detailed description of developed Flex-SPI firmware structure together with experimental tests carried out by using ad-hoc instrumental setups based on TI MSP-EXP430F5438 experimenter boards. Developed framework, aimed to provide a solid base to test the possibility of performing a shared SPI communication with a fixed number of wires without renouncing to push-pull output stage advantages, has been implemented and successfully validated. Also, FlexSPI energy consumption has been evaluated and then compared with the I2C one, by proper experimental setups and related data processing: the two protocols, in fact, share several features, although they rely on a different hardware configuration. The energy/bit metric was chosen so that the two output stages can be compared regardless the effective quantity of exchanged packets; thus, this measure provides an indication of necessary energy amount to move a single bit to guarantee the correct firmware functionality. Despite larger quantity of exchanged data due to channel reservation needs (with a 35% traffic overhead, in the performed tests), the FlexSPI total energy consumption is comparable with the I2C one, at the same communication speed; thus a lower energy/bit requirement is required for FlexSPI protocol, decreasing with the negotiated speed, in this way proving FlexSPI protocol as a suited and valid choice for high-speed low-consumption communications inside embedded systems with a developed architecture capable of great flexibility.