Soil moisture measurement device

There is one spare Pico ADC, so why not add a further sensor such as a SFH 300 phototransistor for measuring the ambient light.

A rather lackluster attempt to create a protecting layer with cast resin for the PCB bottom side.

Implemented IoT capabilities (via ESP8266), i.e. value(s) can be fetched thru a web-browser. 

Wiring ESP8266 - Pico:

Pin 1: GND
Pin 2 (TXO): Pico GP5 (UART1 RX)
Pin 4: 3.3V
Pin 7 (RXI): Pico GP4 (UART1 TX)
Pin 8: 3.3V
Other pins n.c.

Improved Maths for the capacitive sensor HW-390: the entire 00-99 range on the 7-Segment-Displays will now be used.

Background: Capacitive sensor HW-390 delivers around 3.0V (here: approximately 65.535 after ADC conversion and expansion) output voltage when the soil is completely dry, and 1.0V (here: approximately 21.845 after ADC conversion and expansion) when the soil is completely wet. 

(Source of this schematic: Sensors | Free Full-Text | Characterization of Low-Cost Capacitive Soil Moisture Sensors for IoT Networks (mdpi.com) )