At the 45m final report period, IOT devices that monitor parameters related to grape maturation have been fabricated and tested, and field trials done demonstrating device reliability . IOT devices for monitoring hydric stress were fabricated using both visible and infrared bands (Fig.2 and Fig.3).The fabricated systems ( grape monitoring and water status) include 4 LEDS per module in the uv-visible ( grape monitoring) and visible and NIR ( hydric stress monitoring), an array of photodiodes ( CMOS or a:SiH with monolithically integrated interference filters when required for fluorescence measurements), assembled in a optical microspectrometer head. The assembly has been done either on a PCB or on a polyimide stripe (Fig.2). For monitoring grape maturation, the optical head is placed inside the grape bunch, linked to the external controller and radio communications unit (Fig.3) placed near the trunk. For vine hydric stress monitoring, two concepts were developed to place the optical head near the leaf. The controller and radio communications unit was implemented through initial iterations to allow monitoring during the full campaign ( about 2.5 months). First prototypes in the field used discrete electronics for the optical signal conditioning. An ASIC was developed, tested and deployed in the final optical head prototypes, bringing the signal conditioning near the photodiodes, and was tested in the Summer campaign 2022. A multivariate approach was used to correlate the desired grape parameters with diffuse reflectance at the illuminating wavelengths. For the final correlations, data acquisition in the field was obtained in the summer campaigns of 2020, 2021 and 2022. First correlations between optical data and wet chemical analysis for selected grape varieties was already done ( Brix, potential alcohol, titrable acidity and pH). For water status, thepresent model does not yet allow quantitative prediction of water leaf potential based on the reflectance data.
