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.