Overview

This guide is part of a series of guides that cover the basics of using Adafruit IO. It will show you how to send temperature and humidity values wirelessly to Adafruit IO from a DHT22 sensor.

If you haven't worked your way through the Adafruit IO feed and dashboard basics guides, you should do that before continuing with this guide so you have a basic understanding of Adafruit IO.

You should go through the setup guides associated with your selected set of hardware, and make sure you have internet connectivity with the device before continuing. The following links will take you to the guides for your selected platform.

If you have went through all of the prerequisites for your selected hardware, you are now ready to move on to the Adafruit IO setup steps that are common between all of the hardware choices for this project. Let's get started!

Adafruit IO Setup

The first thing you will need to do is to login to Adafruit IO and visit the Settings page.

Click the VIEW AIO KEY button to retrieve your key.

A window will pop up with your Adafruit IO. Keep a copy of this in a safe place. We'll need it later.

Creating the Feeds

First, you will need to create a feed called Temperature. 

You will also need to create a feed called Humidity.

If you need help getting started with creating feeds on Adafruit IO, check out the Adafruit IO Feed Basics guide.

Adding the Line Chart Block

Add a new Line Chart block to a new or existing dashboard. Make sure you have selected both the Temperature and Humidity feeds as the data sources for the block.

When you reach the block settings, set the Hours of History setting to 24 hours, and name the block whatever you would like.

When you are finished editing the form, click Create Block to add the new block to the dashboard.

If you need help getting started with Dashboards on Adafruit IO, check out the Adafruit IO Dashboard Basics guide.

Next, we will look at wiring the circuit.

Arduino Wiring

You will need the following parts for this tutorial:

  • 1x Adafruit IO compatible Feather
  • 1x DH22 temperature & humidity sensor
  • 1x 10k ohm resistor
  • 4x jumper wires

We will need to connect the following pins from the Feather to the resistor and DHT22:

* Feather 3V to Pin 1 of the DHT22
* Feather 3V to one leg of a 10k ohm resistor, and the other leg of the resistor to Pin 2 of the DHT22
* Feather Pin 2 to Pin 2 of the DHT22
* Feather GND to Pin 4 of the DHT22

Arduino Setup

You should go through the setup guides associated with your selected set of hardware, and make sure you have internet connectivity with the device before continuing. The following links will take you to the guides for your selected platform.

You will need to make sure you have at least version 2.4.1 of the Adafruit IO Arduino library installed before continuing.

You will also need to install the Adafruit Unified Sensor library.

As well as the DHT Sensor Library.

For this example, you will need to open the adafruitio_15_temp_humidity example in the Adafruit IO Arduino library.

Next, we will look at the network configuration options in the sketch.

Arduino Network Config

To configure the network settings, click on the config.h tab in the sketch. You will need to set your Adafruit IO username in the IO_USERNAME define, and your Adafruit IO key in the IO_KEY define.

WiFi Config

WiFi is enabled by default in config.h so if you are using one of the supported WiFi boards, you will only need to modify the WIFI_SSID and WIFI_PASS options in the config.h tab.

FONA Config

If you wish to use the FONA 32u4 Feather to connect to Adafruit IO, you will need to first comment out the WiFi support in config.h

Next, remove the comments from both of the FONA config lines in the FONA section of config.h to enable FONA support.

Ethernet Config

If you wish to use the Ethernet Wing to connect to Adafruit IO, you will need to first comment out the WiFi support in config.h

Next, remove the comments from both of the Ethernet config lines in the Ethernet section of config.h to enable Ethernet Wing support.

Next, we will look at how the example sketch works.

Arduino Code

The adafruitio_15_temp_humidity example uses digital pin 2 by default on all boards, and that can be modified if needed by changing the DATA_PIN define.

Download: file
// pin connected to DH22 data line
#define DATA_PIN 2

The next chunk of code creates an instance of the DHT class, and also sets up feed instances for the temperature and humidity feeds.

Download: file
// create DHT22 instance
DHT_Unified dht(DATA_PIN, DHT22);

// set up the 'temperature' and 'humidity' feeds
AdafruitIO_Feed *temperature = io.feed("temperature");
AdafruitIO_Feed *humidity = io.feed("humidity");

The setup function initializes the DHT22 sensor, and also connects your feather to Adafruit IO. The code will wait until you have a valid connection to Adafruit IO before continuing with the sketch. If you have any issues connecting, check config.h for any typos in your username or key.

Download: file
void setup() {

  // start the serial connection
  Serial.begin(115200);

  // wait for serial monitor to open
  while(! Serial);

  // initialize dht22
  dht.begin();

  // connect to io.adafruit.com
  Serial.print("Connecting to Adafruit IO");
  io.connect();

  // wait for a connection
  while(io.status() < AIO_CONNECTED) {
    Serial.print(".");
    delay(500);
  }

  // we are connected
  Serial.println();
  Serial.println(io.statusText());

}

Next, we have the main loop() function. The first line of the loop function calls io.run(); this line will need to be present at the top of your loop in every sketch. It helps keep your device connected to Adafruit IO, and processes any incoming data.

Download: file
void loop() {

  // io.run(); is required for all sketches.
  // it should always be present at the top of your loop
  // function. it keeps the client connected to
  // io.adafruit.com, and processes any incoming data.
  io.run();

The next chunk of code inside the loop() checks the current DHT22 temperature value, and saves the value in the celsius and fahrenheit variables.

We then print both celsius and fahrenheit to the Arduino Serial Monitor, and save the fahrenheit value to the temperature feed on Adafruit IO.

Download: file
  sensors_event_t event;
  dht.temperature().getEvent(&event);

  float celsius = event.temperature;
  float fahrenheit = (celsius * 1.8) + 32;

  Serial.print("celsius: ");
  Serial.print(celsius);
  Serial.println("C");

  Serial.print("fahrenheit: ");
  Serial.print(fahrenheit);
  Serial.println("F");

  // save fahrenheit (or celsius) to Adafruit IO
  temperature->save(fahrenheit);

If you prefer to log celsius values, you can modify the call to the save() function.

Download: file
temperature->save(celsius);

The final chunk of the loop() function requests a humidity reading from the DHT22, and prints the value to the Arduino Serial Monitor. We also save the humidity value to the humidity feed on Adafruit IO.

Download: file
  dht.humidity().getEvent(&event);

  Serial.print("humidity: ");
  Serial.print(event.relative_humidity);
  Serial.println("%");

  // save humidity to Adafruit IO
  humidity->save(event.relative_humidity);

  // wait 5 seconds (5000 milliseconds == 5 seconds)
  delay(5000);

}

Upload the sketch to your board, and open the Arduino Serial Monitor. Your board should now connect to Adafruit IO.

Download: file
Connecting to Adafruit IO....

Adafruit IO connected.

You should now see the temperature and humidity values being sent to Adafruit IO.

Download: file
celsius: 18.30C
fahrenheit: 64.94F
humidity: 34.90%
  
celsius: 18.20C
fahrenheit: 64.76F
humidity: 35.40%

Check your dashboard on Adafruit IO, and you should see the line chart update with the changes in temperature and humidity.

Add an OLED

Now that you've got a graphing weather device using IO, you can add an OLED feather so you can see network status, IP address, and the latest measurements!

Plug the OLED FeatherWing on top of your Feather, and check out our guide to get set up and test it! Once you've verified that the OLED works, you can use this new code. Use the same config.h file from the previous section, just replace the 'main' tab of code:

This is just the main code, and does not include the config.h - use the same config.h you had from the previous working demo!
Download: file
// Adafruit IO Temperature & Humidity Example
// Tutorial Link: https://learn.adafruit.com/adafruit-io-basics-temperature-and-humidity
//
// Adafruit invests time and resources providing this open source code.
// Please support Adafruit and open source hardware by purchasing
// products from Adafruit!
//
// Written by Todd Treece for Adafruit Industries
// Copyright (c) 2016-2017 Adafruit Industries
// Licensed under the MIT license.
//
// All text above must be included in any redistribution.

/************************** Configuration ***********************************/

// edit the config.h tab and enter your Adafruit IO credentials
// and any additional configuration needed for WiFi, cellular,
// or ethernet clients.
#include "config.h"

/************************ Example Starts Here *******************************/
#include <Adafruit_Sensor.h>
#include <DHT.h>
#include <DHT_U.h>
#include <Adafruit_SSD1306.h>

// oled display
Adafruit_SSD1306 oled = Adafruit_SSD1306(128, 32, &Wire);

// pin connected to DH22 data line
#define DATA_PIN 2

// create DHT22 instance
DHT_Unified dht(DATA_PIN, DHT22);

// set up the 'temperature' and 'humidity' feeds
AdafruitIO_Feed *temperature = io.feed("temperature");
AdafruitIO_Feed *humidity = io.feed("humidity");

void setup() {
  oled.begin(SSD1306_SWITCHCAPVCC, 0x3C);  // initialize with the I2C addr 0x3C (for the 128x32)
  oled.display();

  // start the serial connection
  Serial.begin(115200);

  // wait for serial monitor to open
  while(! Serial);

  // initialize dht22
  dht.begin();

  // connect to io.adafruit.com
  Serial.print("Connecting to Adafruit IO");
  io.connect();

  // wait for a connection
  while(io.status() < AIO_CONNECTED) {
    Serial.print(".");
    delay(500);
  }

  // we are connected
  Serial.println();
  Serial.println(io.statusText());

  // text display tests
  oled.setTextSize(1);
  oled.setTextColor(WHITE);
}

void loop() {

  // io.run(); is required for all sketches.
  // it should always be present at the top of your loop
  // function. it keeps the client connected to
  // io.adafruit.com, and processes any incoming data.
  io.run();

  sensors_event_t event;
  dht.temperature().getEvent(&event);

  float celsius = event.temperature;
  float fahrenheit = (celsius * 1.8) + 32;

  Serial.print("celsius: ");
  Serial.print(celsius);
  Serial.println("C");

  Serial.print("fahrenheit: ");
  Serial.print(fahrenheit);
  Serial.println("F");

  // save fahrenheit (or celsius) to Adafruit IO
  temperature->save(fahrenheit);

  dht.humidity().getEvent(&event);
   
  Serial.print("humidity: ");
  Serial.print(event.relative_humidity);
  Serial.println("%");

  // save humidity to Adafruit IO
  humidity->save(event.relative_humidity);

  // print it to the OLED
  oled.clearDisplay();
  oled.setCursor(0,0);
  oled.print("SSID: "); oled.println(WIFI_SSID);
  oled.print("IP: "); oled.println(WiFi.localIP());
  oled.print("Temp: "); oled.print(fahrenheit,0); oled.print(" *F ");
  oled.print("Hum: "); oled.print(event.relative_humidity,0); oled.println(" %");
  oled.print("IO Status: ");
  aio_status_t aio_status = io.status();
  Serial.print("Status: "); Serial.println(aio_status);
  switch (aio_status) {
     case AIO_IDLE:  oled.println("IDLE"); break;
     case AIO_DISCONNECTED:
     case AIO_NET_DISCONNECTED:  oled.println("DISCONNECT"); break;
     case AIO_NET_CONNECTED:
     case AIO_CONNECTED_INSECURE:
     case AIO_CONNECTED: oled.println("CONNECTED"); break;
  }
  oled.display();

  // wait 5 seconds (5000 milliseconds == 5 seconds)
  delay(2000);
}

Python Wiring

We're going to use a combination of the Adafruit IO Client Library and Adafruit's CircuitPython to control a Raspberry Pi over Adafruit IO. 

Parts

1 x Raspberry Pi 3 - Model B+
The Raspberry Pi is a small linux board compatible with Adafruit IO projects.

If you're following along with a Raspberry Pi, we're going to use a T-Cobbler Plus for the IO Basics Projects. This add-on prototyping board lets you easily connect a Raspberry Pi (Raspberry Pi Model Zero, A+, B+, Pi 2, Pi 3) to a solderless breadboard:

Assembled Pi T-Cobbler Plus - GPIO Breakout

PRODUCT ID: 2028
This is the assembled version of the Pi T-Cobbler Plus.  It only works with the Raspberry Pi Model Zero, A+, B+, Pi 2,Pi 3! (Any Pi with 2x20 connector)
$7.95
IN STOCK

We'll also need a temperature and humidity sensor. The DHT22 is a low-cost temperature and humidity sensor which is easy to wire up. You'll also need a 10k ohm resistor. 

DHT22 temperature-humidity sensor + extras

PRODUCT ID: 385
The DHT22 is a basic, low-cost digital temperature and humidity sensor. It uses a capacitive humidity sensor and a thermistor to measure the surrounding air, and spits out a digital...
$9.95
IN STOCK

Wiring

Make the following connections between the Pi and the DHT22:

  • Pi 3.3V to DHT Pin 1
  • Pi Digital Pin 26 to DHT Pin 2
  • Pi GND to DHT Pin 4
  • 10k ohm resistor (left pin) to DHT Pin 2
  • 10k ohm resistor (right pin) to GND

Python Setup

If you've been following along with the IO Basics: Python guides, we are not using Adafruit Blinka for this specific tutorial. Blinka doesn't have a special timing module called pulseio (yet!). 

Instead, we are going to use the Adafruit Python DHT Sensor Library and the Adafruit IO Python Client Library.

The latest Raspbian (currently this is `Stretch`) is required for the installation of Adafruit IO + Blinka.

Update your Pi and Python

We'll assume you've already gotten your Raspberry Pi up and running and can log into the command line.

Go ahead and ssh into your Raspberry Pi via terminal or a ssh client:

ssh [email protected]

Run the standard updates:

sudo apt-get update

sudo apt-get upgrade

and

sudo pip3 install --upgrade setuptools

Make sure you're using Python 3!

The default python on your computer may not be python 3. Python 2 is officially discontinued and all our libraries are Python 3 only.

We'll be using python3 and pip3 in our commands, use those versions of python and pip to make sure you're using 3 and not 2

Installing Adafruit Python DHT Library

We're ready to install the Adafruit Python DHT Library. This library will allow our Raspberry Pi to read the temperature and humidity values from the DHT22. We'll use pip to install the library from PyPi. 

Enter the following in your terminal to install the Adafruit Python DHT Library:

sudo pip3 install Adafruit_DHT

Installing Adafruit IO Python Library

We'll also need to install the Adafruit IO Python Client Library to communicate with Adafruit IO.

Run the following command to install the Adafruit IO Client for Python:

pip3 install adafruit-io

If the installation gives you 'insufficient permissions' errors, add 'sudo' before the call to pip3

Downloading Example Code

The example code is contained within the Adafruit IO Python Client's examples/basics subdirectory.

Navigate to the root directory of the Pi by entering the following in the terminal:

cd ~

Download the latest version of the Adafruit IO Python Client's GitHub repository by running

git clone https://github.com/adafruit/io-client-python.git

Navigate to the folder's example code for the examples

cd io-client-python/examples/basics/

Python Code

The temp_humidity.py code uses Raspberry Pi GPIO Pin 26 by default. If you'd like to use a different pin, change the DHT_DATA_PIN variable.

DHT_DATA_PIN = 26

Before running, we'll need to set our Adafruit IO Key and Adafruit IO Username. You can find both of these on your Adafruit IO profile page

Download: file
# Set to your Adafruit IO key.
# Remember, your key is a secret,
# so make sure not to publish it when you publish this code!
ADAFRUIT_IO_KEY = 'YOUR_AIO_KEY'

# Set to your Adafruit IO username.
# (go to https://accounts.adafruit.com to find your username).
ADAFRUIT_IO_USERNAME = 'YOUR_AIO_USERNAME'

The next chunk of code creates an instance of the Adafruit IO REST client, sets up the temperature and humidity feeds, and sets up the DHT22 sensor.  

Download: file
# Create an instance of the REST client.
aio = Client(ADAFRUIT_IO_USERNAME, ADAFRUIT_IO_KEY)

# Set up Adafruit IO Feeds.
temperature_feed = aio.feeds('temperature')
humidity_feed = aio.feeds('humidity')

# Set up DHT22 Sensor.
dht22_sensor = Adafruit_DHT.DHT22

in the while True loop, we first try to grab the humidity and sensor readings using Adafruit_DHT.read_retry which retries (up to 15 times) to get a sensor reading.

Download: file
humidity, temperature = Adafruit_DHT.read_retry(sensor, DHT_DATA_PIN)

If the DHT sensor receives a reading, it'll print out both of the values and send them to the Adafruit IO temperature and humidity feeds.

Download: file
print('Temp={0:0.1f}*C Humidity={1:0.1f}%'.format(temperature, humidity))
aio.send(temperature.key, temperature)
aio.send(humidity.key, humidity)

Sometimes you won't get a sensor reading and the results will be null (because Linux can't guarantee the timing of calls to read to the sensor). If that occurs, we'll print to the terminal. Then, we sleep for DHT_READ_TIMEOUT until the next read.

In your terminal, enter the following command to run the code:

python3 temp_humidity.py

You should now see the temperature and humidity values being sent to Adafruit IO.

Download: file
Temp=25.5*C Humidity=59.1%
Temp=25.5*C Humidity=59.1%
Temp=25.5*C Humidity=59.1%
Temp=25.4*C Humidity=59.0%

Check your dashboard on Adafruit IO, and you should see the line chart update with the changes in temperature and humidity.

Code

"""
'temp_humidity.py'
==================================
Example of sending analog sensor
values to an Adafruit IO feed.

Author(s): Brent Rubell

Tutorial Link: Tutorial Link: https://learn.adafruit.com/adafruit-io-basics-temperature-and-humidity

Dependencies:
    - Adafruit IO Python Client
        (https://github.com/adafruit/io-client-python)
    - Adafruit_Python_DHT
        (https://github.com/adafruit/Adafruit_Python_DHT)
"""

# import standard python modules.
import time

# import adafruit dht library.
import Adafruit_DHT

# import Adafruit IO REST client.
from Adafruit_IO import Client, Feed

# Delay in-between sensor readings, in seconds.
DHT_READ_TIMEOUT = 5

# Pin connected to DHT22 data pin
DHT_DATA_PIN = 26

# Set to your Adafruit IO key.
# Remember, your key is a secret,
# so make sure not to publish it when you publish this code!
ADAFRUIT_IO_KEY = 'YOUR_AIO_KEY'

# Set to your Adafruit IO username.
# (go to https://accounts.adafruit.com to find your username).
ADAFRUIT_IO_USERNAME = 'YOUR_AIO_USERNAME'

# Create an instance of the REST client.
aio = Client(ADAFRUIT_IO_USERNAME, ADAFRUIT_IO_KEY)

# Set up Adafruit IO Feeds.
temperature_feed = aio.feeds('temperature')
humidity_feed = aio.feeds('humidity')

# Set up DHT22 Sensor.
dht22_sensor = Adafruit_DHT.DHT22

while True:
    humidity, temperature = Adafruit_DHT.read_retry(dht22_sensor, DHT_DATA_PIN)
    if humidity is not None and temperature is not None:
        print('Temp={0:0.1f}*C Humidity={1:0.1f}%'.format(temperature, humidity))
        # Send humidity and temperature feeds to Adafruit IO
        temperature = '%.2f'%(temperature)
        humidity = '%.2f'%(humidity)
        aio.send(temperature_feed.key, str(temperature))
        aio.send(humidity_feed.key, str(humidity))
    else:
        print('Failed to get DHT22 Reading, trying again in ', DHT_READ_TIMEOUT, 'seconds')
    # Timeout to avoid flooding Adafruit IO
    time.sleep(DHT_READ_TIMEOUT)

Adafruit IO FAQ

Encountering an issue with your Adafruit IO Arduino Project?

If you're having an issue compiling, connecting, or troubleshooting your project, check this page first.

Don't see your issue?  Post up on the Adafruit IO Forum with your issue.

I encounter the following error when compiling my sketch:

  fatal error: Adafruit_MQTT.h: No such file or directory, #include "Adafruit_MQTT.h"

The Adafruit IO Arduino library is dependent on our Adafruit IO MQTT Library.

To resolve this error, from the Arduino IDE, navigate to the Manage Libraries... option in the Sketch -> Include Library menu.

To resolve this error, from the Arduino IDE, navigate to the Manage Libraries... option in the Sketch -> Include Library menu.

My Serial Monitor prints "..." endlessly after the "Connecting to Adafruit IO" message

Your board is not connecting to Adafruit IO, but why? Let's find out:

First, check in config.h that you have the correct IO_USERNAMEIO_KEYWIFI_SSID, and WIFI_PASS are set correctly. 

Next, we're going to modify the while loop which waits for an IO connection in your sketch. Change the line in the status check loop from Serial.println(.);to Serial.println(io.statusText());

// wait for a connection
while(io.status() < AIO_CONNECTED) {
Serial.println(io.statusText());
delay(500);
}

Verify and re-upload the sketch. If you're receiving a Network disconnected error message, the board is not able to talk to the internet. Re-check your hardware, connections, and router settings. 

If it's still not showing Adafruit IO connected, check the IO status on the Adafruit Status page to make sure the service is online.

My data isn't displaying, is Adafruit IO's {service/MQTT/API} down?

Possibly - you can check IO status on the Adafruit Status page

Is my data being sent properly? Am I sending too much data?

There's a monitor page built-into Adafruit IO which provides a live view of incoming data and error messages. Keep this page open while you send data to your Adafruit IO devices to monitor data and errors. 

This guide was first published on Feb 20, 2017. It was last updated on Feb 20, 2017.