Author: Nathan

In my previous “New Toy” post I managed to wirelessly publish a count, so I determined the next step to be to publish some “real” information: the temperature.

I’m not the first to use an ESP8266 module to publish temperature information and I found an excellent tutorial on Adafruit.  However, it was written for another (now discontinued) ESP8266 module with significant differences from my Electrow.  Also, the sample code provide has the module host a web server and allow clients to connect to it whereas I wanted my module to push the information to a database.  This meant I could use the tutorial as a guide, but there were still various things to figure out.

First I had to do the wiring to connect the DHT22 temperature and humidity sensor I purchased like the one used in the tutorial.  I ended up spending a lot of time and muttering various working words trying to get it to work right.  My module has onboard USB and a voltage regulator, so the wiring is much simpler, but I couldn’t get any readings.  I tried resistor changes, testing connections, and verifying voltages among other things.  Finally I discovered that when I specify pin 2 it means D04 (the fifth digital pin) on my board.  So here’s what I ended up with:

• The ground pin connects to the fourth pin of the DHT22 (black wire)
• The D04 digital pin connects to the second pin of the DHT22 (white wire)
• The 3.3v pin provides voltage (via the red wire) to the both the first pin of the DHT22 and it also goes through a 10K resister to the second pin.

The code is basically pasting together the Adafruit sample code with the code I wrote previously.  It looks like this:

#include <ESP8266WiFi.h>
#include <DHT.h>
#define DHTTYPE DHT22
#define DHTPIN  2

const char* ssid = "name of wifi network";
const char* pass = "wifi network password";
const char* ip = "192.168.1.35";
const int port = 7379;

// Initialize DHT sensor 
DHT dht(DHTPIN, DHTTYPE, 11); // 11 works fine for ESP8266
 
void setup(void)
{
  dht.begin();
  WiFi.begin(ssid, pass);
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
  }
}
 
void loop(void)
{
    float temp_f = dht.readTemperature(true);

    WiFiClient client;
    client.connect(ip, port);
    String url = String("/SET/temperature/") + temp_f;
    client.print(String("GET ") + url + " HTTP/1.1\r\n" +
           "Host: " + String(ip) + "\r\n" + 
           "Connection: close\r\n" + 
           "Content-Length: 0\r\n" + 
           "\r\n");
    delay(5000);
} 

I had already started up a Webdis/Redis server as described before, so I could verify it worked by running curl and confirming that it returned a value (in this case 72.68F).

$ curl http://192.168.1.35:7379/GET/temperature
{"GET":"72.68"}

Searching online, I found the ConnectSense CS-TH Wireless Temperature and Humidity Sensor that seems pretty much like what I made, but in a pretty box and costing $150 (granted it does come with some nice software as well).  Now that I have my own budget version, I can look to do something with that temperature data I’m collecting.

Today my new toy arrived.  It’s an ESP8266 IOT WiFi Module.

Specifically I selected the “Elecrow ESP8266 IOT Board WiFi Module with Built in USB and Battery Charging” out of the many ESP8266 variants because of the following features:

• Onboard USB (I find it easier than FTDI)
• NOT breadboard friendly (Pins sticking up not down)
• In stock and eligible for Prime shipping

To start with, I just wanted to verify that I could run some code on it.  Here’s what I did:

1. Installed the Arduino IDE from https://www.arduino.cc/en/Main/Software.  I used the latest available (1.6.9).
2. Configured the Arduino IDE to support ESP8266 boards:
   1. Opened up the preferences and added http://arduino.esp8266.com/versions/2.3.0/package_esp8266com_index.json to the “Additional Boards Manager URLs”.
   2. Opened the “Boards Manager”, found the “esp8266” listing, and clicked the “Install” button (using the latest 2.3.0 version).
   3. Since there wasn’t a specific Electrow entry, I selected “Generic ESP8266 Module” for the board type.
3. Wrote some code.  Here is my very simple sketch to slowly count and send the number via serial:

   int count = 0;
    void setup() {
    Serial.begin(9600);
    }
    void loop() {
    Serial.println(count++);
    delay(1000);
    }

4. Ran the code.  I uploaded it to the module, opened the serial terminal, and saw that it was counting as designed.
   

Of course it took a bit of kicking and swearing to do that.  Here are a few of the things that I did before everything worked:

1. Ran the Arduino IDE as root
2. The upload speed is 115200, but the terminal speed is 9600 baud
3. Change the reset method to “nodemcu”.
4. Sometimes (but not always) hold the flash button and than hit the reset button before I could successfully upload my sketch.
5. Switch USB cords (the first is a cheap, old cord that in recent years has only been used for charging devices).
6. Check the port whenever I plugged in the module (it sometimes switched between /dev/ttyUSB0 and /dev/ttyUSB1 just to spite me).

There’s nothing exciting about my counting program, but by getting it running I confirmed that I can 1) Connect to the module 2) Upload code to it and 3) Run the code.  Now that I can do that, I can see what else I can make my new toy do . . .