Thanks to a robust software architecture, it is able to provide many features that can be used by smart objects to enhance their capabilities. In this way, sensors and actuators or, more in general, subsystems, can quickly exchange data and efficiently react to malfunctioning; moreover, number of devices on bus can be safely increased even while smart object is performing operations.

In this paper, we report on hardware structure, operation mode and software development for a new advanced communication protocol whose aim is obtaining a fully shared SPI bus with a fixed amount of wires, without renouncing to advantages of a push-pull output stage and obtaining an architecture capable of great flexibility. All four signals of a classic SPI protocol are entirely shared by the slaves on bus: when a master wants to communicate with a particular device, it will perform an addressing at packet level: starting from its main characteristics, various adopted solutions to realize a shared SPI bus will be analyzed, explaining how a communication session is performed. The firmware structure was designed as a software stack composed by interacting layers, tracing model of similar protocols that share with FlexSPI some features. Some of the advanced procedures that can be performed thanks to this protocol will be discussed, highlighting the suitability of FlexSPI for dynamic smart objects; in fact, by adding these features to developed framework, it is possible to explore and appreciate expandability of this communication protocol, making it suitable to meet advanced IoT requirements of smart objects. FlexSPI can be built like aMAC layer above the SPI bus, to process all necessary pieces of information to perform the packet level addressing, using a stack having a layered architecture. This is idea followed in the firmware development, to implement this communication protocol, experimentally verified in the performed and reported communication tests, confirming that it is possible to obtain a shared push-pull bus.

An innovative low-cost device based on hyperspectral spectroscopy in the near infrared (NIR) spectral region is proposed for the non-invasive detection of moldy core (MC) in apples. The system, based on light collection by an integrating sphere, was tested on 70 apples cultivar (cv) Golden Delicious infected by Alternaria alternata, one of the main pathogens responsible for MC disease. Apples were sampled in vertical and horizontal positions during five measurement rounds in 13 days’ time, and 700 spectral signatures were collected. Spectral correlation together with transmittance temporal patterns and ANOVA showed that the spectral region from 863.38 to 877.69 nm was most linked to MC presence. Then, two binary classification models based on Artificial Neural Network Pattern Recognition (ANN-AP) and Bagging Classifier (BC) with decision trees were developed, revealing a better detection capability by ANN-AP, especially in the early stage of infection, where the predictive accuracy was 100% at round 1 and 97.15% at round 2. In subsequent rounds, the classification results were similar in ANN-AP and BC models. The system proposed surpassed previous MC detection methods, needing only one measurement per fruit, while further research is needed to extend it to different cultivars or fruits.

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 I 2 C 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 I 2 C 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.