Moisture and Temperature Sensor on a Pulsed Current Loop (CAT5 pair). An RPUno has a pulse sensor input, it has a 17mA current source which will saturate to supply the loop that runs a 3 or 10 mA. The RPUno also has a 100-ohm termination resistor used to bias the base of on open collector that can pull down the ICP1 pin of the ATmega328. The input capture hardware measures events that are a function of the MT's capacitive sensor driven by a 555 timer.
Development page https://github.com/epccs/LoopSensor/tree/master/MT
Firmware for Capture on an RPUno: https://github.com/epccs/RPUno/tree/master/Capture
Capacitive moisture and temperature
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