To get started, a few additional libraries need to be added to the Arduino IDE in order to work with the DHT sensor. Those two items are:

• DHT sensor library
• Adafruit Unified Sensor library

The DHT sensor library are drivers and classes for working with DHT sensors, and the Adafruit unified sensor library combines sensor data into a single 'type' while abstracting details for all the different sensors. What this provides is the ability to take any supported sensor and plug it in and it should work. Pretty sweet.

DHT Sensor Library

We'll begin by installing the DHT library first. In the Arduino IDE, click on the Sketch menu, then select Include Library -> Manage Libraries, as shown in Figure 1.

Figure 1

In the Library Manager dialog, type in DHT Sensor Library in the search box, as shown in Figure 2. Click the DHT sensor library, select the version, then click Install. When I built this solution, version 1.2.3 was the latest, but in checking at the time of this writing, version 1.3.0 is the latest. Either should work.

Figure 2

Once the DHT sensor library is installed, click Close on the Library Manager dialog.

Unified Sensor Driver

Now do the same thing for the Adafruit DHT Unified library but the install for this is a little different. Open your favorite browser and navigate to the following URL:

https://github.com/adafruit/Adafruit_Sensor

On the Adafruit sensor page, click green Clone or download link, and select Download ZIP, as shown in Figure 3, and save it to a location on your PC. The file will be called Adafruit-sensor-master.zip.

Figure 3

Back in the Arduino IDE, click on the Sketch menu, the select Include Library -> Add .ZIP Library, as shown in Figure 4.

Figure 4

Browse to the location where you saved the zip file and select it, then click Open. The Arduino will install the necessary library into the IDE. The install is very short, and you can verify that both the DHT sensor and the Adafruit Unified Sensor libraries have both been successfully installed by selecting Include Library from the Sketch menu, and you will see both listed in the Recommended libraries section of the menu, as shown in Figure 5.

Figure 5

At this point, it's time to hook up the sensor and write the code to read the sensor data.

Hooking up the Sensor

Figure 6 shows how I hooked up the sensor to the Arduino board. The DHT22 sensor needs to be wired up as follows:

• Pin 1 of the DHT22 sensor connects to the VCC (3 to 5V power) on the Arduino (red wire)
• Pin 2 of the DHT22 is the data pin and connects to pin 2 on the Arduino (white wire)
• Ignore pin 3
• Pin 4 of the DHT22 is the ground pin and connects to ground on the Arduino (black wire)

Next, place a 10K resistor between the VCC (power) and data pin. This will act as a medium-strength pull on the data line.

Figure 6

Once you have the sensor hooked up, it's time to write some code.

The Code

If you don't want to write any code, that's good because it's already been written for you. Simply go to https://learn.adafruit.com/dht/downloads and click on the Arduino library and example code for DHT sensors link. This will download a .ZIP file called DHT-sensor-library-master, and in that zip file is a library and example scripts for testing the DHT sensors. Extract the zip file into a directory and navigate to the \examples\DHTtester folder. Open the file in that directory called DHTtester in the Arduino IDE. Notice that it has support for the DHT11 and DHT22 sensors. Simply uncomment the sensor type you are using (in this case the DHT22). Also notice that in this file, all sensor data is sent to the output logs via Serial.print.

You're ready to go! Plug in the Arduino board (as shown in Figure 6) and give it a minute to boot. While it's booting, click the Verify button to compile the sketch. Once it has compiled, click the Upload button to deploy the code to the Arduino board. While it is uploading, select Serial Monitor from the Tools menu which will allow you to see the logs and data read (which is where the Serial.print statements are sending the data). Once the code is uploaded, the Arduino will start reading the DHT sensor data and outputting the results to the serial monitor, as shown in figure 7.

Figure 7

There you go, you are up and running! The next blog post in this series will modify the code to send the sensor data to Azure.

Code Snippet

'use strict';

Code Snippet

var https = require('https'); var crypto = require('crypto'); var tessel = require('tessel'); var climatelib = require('climate-si7020'); //var moment = require('moment'); var climate = climatelib.use(tessel.port['A']);

To get started, you first need to download a couple of items:

1. Latest Arduino IDE Software here.
2. CP2104 USB driver here.

The USB driver is needed to have the COM/Serial port appear and work properly with the Arduino board, and the Arduino IDE is used to configure the Arduino board as well as to author and deploy code to the board.

I don't think it matters when the Arduino needs to be connected, but I installed the software first because it recommends that you restart the PC after installing and configuring everything. Thus, go ahead and install both the Arduino IDE software and the USB driver software. The USB driver install is extremely quick and the Arduino IDE install isn't much longer.

Once the installs complete, launch the Arduino IDE program because you need to select and configure the appropriate board. From the Tools menu, you'll notice that the Adafruit feather HAZZAH ESP8266 board is not listed.

Thus, the next step is to install the ESP8266 Board package which includes all the necessary drivers to communicate with the HAZZAH board. So, from the File menu, select Preferences and enter the following URL into the Additional Boards Manager URL box:

http://arduino.esp8266.com/stable/package_esp8266com_index.json

Click OK on the Preferences dialog, then from the Tools menu, select Board -> Boards Manager

In the Boards Manager dialog, scroll down to the very bottom of the list and select the esp8266 by ESP8266 Community driver and click Install. The latest version is 2.3.0.

Once the installation is complete, close the Boards Manager dialog and then close the Arduino IDE program. At this point I would reboot the PC. Is it necessary? I have no idea but I did it anyway. Plus, one of the web sites says "When you've restarted, …" but it doesn't say what to restart. One can assume, but hey…

Anyway, once you're restarted whatever you restarted, plug in the HAZZAH to the breadboard then connect the HAZZAH to power via the USB cable.

Next, start up the Arduino IDE again and from the Tools menu, select Board: and you'll see the Adafruit HAZZAH ESP8266 listed.

Next, from the Tools menu, you'll need to configure the CPU Frequency, Flash Size, Upload Speed, and Port. For the HAZZAH ESP8266, select 80 MHz for the CPU Frequency, and4M (3M SPIFFS) for the Flash Size. For the Upload speed, I have selected 256000, but it works great with 115200 as well and according to the documentation, 921600 also works but may fail on occasion. I have had great success with 256000. For the Port, select the appropriate port your HUZZAH is plugged in to.

At this point your configuration is all set and it's time to run a test. Back in the Arduino IDE, replace the default code in the Sketch window with the following code, then click the Upload button. The IDE will ask you to save the file. You don't need to, simply click cancel and it will still deploy the code to the Feather HUZZAH (it just won't save the file).

To get started, you first need to download a couple of items:

1. Node.js version 4.4.4 from here.
2. Zadig USB driver installation tool from here.

Don't plug in your Tessel yet, but install Node.js and the Zadig USB driver. Next, open a command prompt as Administrator.

Next connect your Tessel via the USB. A lot of the forum posts state that you need to hold down the reset button on the Tessel to put it in DFU mode but I did not need to do this and I'll explain why shortly.

Once the Tessel is connected, run the Zadig tool and simply accept all the default on the screen and click the Install button. The Zadig application is a simple tool that installs generic USB drivers, including WinUSB. Installing these drivers allows the Tessel to more efficiently communicate over USB. This process will only take a few seconds.

Return to the command prompt and type in the following to install the Tessel client:

npm i -g t2-cli

Once the client drivers are installed, type in the following command to list your Tessel:

t2 list

You should see your Tessel listed along with any others connected to the same network. Next, you need to authorize your Tessel so you can push code to the Tessel and run the code. Thus, type in and run the following command:

t2 provision

At this point you are up and running. You can test your Tessel by running the Blinky example here. A fun sensor to test is the climate sensor or any of the other Tessel sensors.

As a closing note, you may need a few extra steps if you aren't installing on a clean Windows 10 machine. You may need to download and unzip this zip file, unplug your Tessel, run node driver-clean.js from the zip file, then plug in your Tessel and run run Zadig and the rest of the steps. From the majority of the posts I have read, Tessel works best with Node v4.4.4. Let me know if you have any questions and we'll try and get you up and running. J

Again, thank you to all the fine folks at Tessel and on the forums who were the real workhorses on this!