The device is very easy to setup but I suspect not very accurate for data logging .
VCC = 3.3 - 5V
GND = GND
DO = Digital Out
AO = Analog Out
The analog output will will go from high to low with increasing moisture on the probe.
The digital output will go high when the moisture level reaches a threshold set with the pot.
I have tested this just a little and it seems to be functional as a plant watering indicator. I put the probe into the soil around a plant and added water to the soil to bring it to the moisture content I usually use. I then set the pot to a level that just turns the onboard LED on. I use the digital out to trigger a digital in on an ESP8266 which sends a signal to another ESP8266 that controls several water solenoids.
For a data logger I think you could probably use the analog output coupled to a Arduino, ESP8266, Pi or any micro-controller with analog inputs and convert that to a digital value.
Using Wemos board A0 is capable of 3.3 input. I am using 3.3V output on Wemos to power the TE215 and A0 of TE215 directly drives A0 of Wemos. Works good so far. Current draw of TE215 is about 1~2 mA.