Saturday, 21 October 2017

ESP8266 / nodeMCU and DHT11

October 21, 2017

This will be a short post. This will have a date on it, I am sure. But, I am posting material that will likely become dated soon, so I want that in the text of the post as well.

The ESP8266 IC is a great boon to the electronics hobbyist. I have been using a nodeMCU version lately and have had some good amount of success although there has been a lot of digging to get things to work correctly.

While using information found on the Web is usually free, I still like books. So, I bought a book: "Internet of Things with ESP8266," by Marco Schwartz - in PDF.

After spending several hours on the small project of getting a DHT11 sensor to work with my nodeMCU, I finally figured out that my DHT libaries were out-of-date. The simple solution was to install Adafruit's DHT library and their Adafruit_Sensor library.

Here is the link to using a DHTXX sensor on Adafruit:

My setup is seen below:

The thing to realize, when you use an ESP8266 module of some sort. is that you need to know what pins are being used in the Arduino code. Here is a typical image of a nodeMCU layout:
A little hint: when you go to write your code in the Arduino IDE, make sure you use the correct pin. Looking at the layout above, D1 is GPIO5. In a typical DHT11 example program you will see digital pin 2 used to get data from the sensor. I changed that to 5, as was in the code in the book. The point is that nodeMCU pins will often not work with with Arduino board code and changes will be needed. Then you also have to make sure you are getting the correct numbers for whatever ESP8266 module you are using.

I will not bother posting the code as you can find it online in different places. Hopefully, it will be enough assistance to those with similar problems in keeping their libraries up-to-date. I guess that is my own lesson as well. If I come across more problems that I are worth posting, I will.

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