Soil sensor appears to have a problem when put to sleep. Resolved by removing power to the sensor when the controlling micro is asleep and then powering the soil sensor fresh every time. I asked the maker for advice but no contact after 10 days.
Aside from that, the sensor is well made and outputs a stable moisture reading.
Response from Catnip electronics | June 6, 2019
I have written two emails to you, but got no response, probably our mailing systems are not playing nice. Can you please file a bug report on github page? https://github.com/Miceuz/i2c-moisture-sensor/issues
Jan. 23, 2018
Problem with ESP8266 - big prpoblem 10 % errors of measuring
The sensor have very strange data collection, there is no possibility to write any program (TASMOTA project used) that will collect proper data , 10 % of getting data is wrong not light only but temperature and moisture.
Hello , we have purchased 5 X I2C soil moisture sensor but unfortunately they do not work as expected. We are using them to measure the VWC in the soil , but the sensor worked for 3 days and later it just stopped working and was giving various indications and not correct. We have compare this sensor with high accuracy sensor and we concluded that the parts we bought are not OK . Hope the manufacturer could give us a solution to this and replace them .
Response from Catnip electronics | Aug. 24, 2016
I will gladly replace you the non-functional sensor, just provide me with your order number. BTW, please note that you have to apply additional coating before use.
The documentation for the I2C interface to this device was very sparse. It took much experimentation to finally get the device to work with my system. Several attempts at communication with the vendor concerning details were left unanswered. In asking the forum the specific questions regarding the interface and how to access the board's LED through the interface, I did get responses but none were helpful. None of the responses addressed the issue of accessing the board's LED. The board's construction was very good, though, with the exception of the edges of the PCB designed to go into the soil. Nothing was done to prevent moisture from leaching into the edges of the PCB over time. I had to put a light coat of paint on the edges of the PCB to seal them against moisture. This could have been done by the manufacturer.