ESP8266 MQTT and DHT22
Posted: Fri Mar 04, 2016 6:32 amI was having nightmares trying to get a DHT22 to read continuously to post to MQTT. It would only read the sensor one then stop! 
If I took out the library ESP8266WiFi..h it would work!!
On testing my program, and getting the adafruit library into debug mode I saw I was getting 'Timeout waiting for start signal low pulse' errors. 
Looking into the code in the file DHT.cpp I found this bit :
// Now start reading the data line to get the value from the DHT sensor.
pinMode(_pin, INPUT_PULLUP);
delayMicroseconds(10); // Delay a bit to let sensor pull data line low.
I kept increasing this value in steps of 5 Microseconds until I got continuous readings. I increased it from 10 and now use a value of 40.
It has now been running for 34 hours and no errors!!!
Hope this helps someone! Its working perfect for me!
Can someone explain why? The datasheets expect everyone to be an expert in this field.
I believe in 'try it and see' 
I added my test code for those who are willing to have a look.
If I took out the library ESP8266WiFi..h it would work!!
On testing my program, and getting the adafruit library into debug mode I saw I was getting 'Timeout waiting for start signal low pulse' errors. Looking into the code in the file DHT.cpp I found this bit :
// Now start reading the data line to get the value from the DHT sensor.
pinMode(_pin, INPUT_PULLUP);
delayMicroseconds(10); // Delay a bit to let sensor pull data line low.
I kept increasing this value in steps of 5 Microseconds until I got continuous readings. I increased it from 10 and now use a value of 40.
It has now been running for 34 hours and no errors!!!
Hope this helps someone! Its working perfect for me!
Can someone explain why? The datasheets expect everyone to be an expert in this field.
I believe in 'try it and see'
I added my test code for those who are willing to have a look.