Soil Humidity - any ideas how to fix the values?

Hi Chris, many thx for your comments. Meanwhile, I added a LDR for sensing the light intesity and I worked a bit on the WiFi stability - e.g. I disconnect from CC3000 and reconnect every 60 sec. It is not perfect, but runs a few hours at some point.

I uploaded my code here for everybody to see:
http://snipt.org/LgFh0

The readSoilSync() function is doing this:

• choose randomly which pin is in/output - this is done to reduce corrosion which was an issue in my last years project
  
• turn on the out pin, read from the in pin - 20 times
  
• average the values
  
• turn off the out pin
  
  

Changing the direction of in/out is mainly due to my last years experiences. I also sent a constant current through the soil last year, which I fixed in this project.

Now, is your idea with resistors and capacitor still valid with this setup? I admit I've not tried it out yet, as I first would like to understand why it makes a differnce if I power it via the power supply compared to the battery. I am planning to do this tonight and before I'll try a few other 5V power supplies (from different phones).

Thx!
Sven