I hooked a DHT22 temperature humidity sensor to the SparkFun ESP8266 Thing Dev Board.Note the 10K pull up resistor. I followed the directions in the SparkFun tutorials. The data logging seems to be working well.
I wanted a No-crawl space monitor.I packaged the board and probe in PVC pipe and bent the pipe to clear the sill plate and get the probe away from the foundation wall. The board lives in the living space and it is easy to route power to it.I needed to pull up a corner of the carpet and drill a hole in the sub-floor plywood.I chose a spot between two crawl space vents. The board gives off a nice red glow that changes color during the probe read every hour.
I ran into the following problems:
To get the program to compile for the ESP8266 I needed to comment out a square root function call in the DHT.CPP library file. I am not using the function that calls the square root.
The program would not download using the Arduino development environment version 166 but worked fine with 164 and 165. See program file attached below.
When you download a .CSV text file to plot in Excel the data is ordered newest first so you must change the order before plotting. The data also has extra spaces between the number and the decimal point like 68 .54 so Excel sees this as text and you cannot plot it. This Excel function =VALUE(SUBSTITUTE(A2," ","")) removes the spaces and changes the text to a number value.