Hey learners! Welcome to another exciting lecture in this series of signals and systems. We are learning about the transform in signals and systems, and in the previous lectures, we have seen a bulk of information about the Laplace transform. If you know the previous concepts of signal and system, then this lecture will be super easy for you to learn, but if your concepts are not clear, do not worry because we will revise all the basic information from scratch for our new readers. So, without wasting time, have a look at the topics of today.
What is z transform?
What is the region of convergence of z transform?
What are some of the important properties of the region of convergence?
How to solve the z transform?
What is an example of the z transform in MATLAB?
What are the methods for the inverse z transform?
You must have an idea that the Laplace transform is a general case transform and converts the signal from a time domain into a frequency domain. The same is the case with the z transform, it changes the domain of the signal but in another way. The Laplace transform is associated with the power signal and the z transform has some other characteristics. Usually, the z transform is used to understand the stability of the system. Z transforms are used in
Energy signals
Power signals
Neither power nor energy signals
Yet it is applicable to a certain level, and after that level, it is not that much more effective. The Z transform is a powerful mathematical tool and is widely used in mathematical courses and applications including signals and systems. We introduce the z transform as:
"The Z transform is a mathematical tool that, after different procedures, converts the differential equation (with time domain) into the algebraic equation of the z domain."
Mathematically, we show it as:
As you can see clearly, the summation sign contains the limits from negative infinity to positive infinity which means it is a bilateral function of the z transform that we have shared with you.
By the same token, you can also predict that the z transform also has another region that lies between the zero to positive infinity. It is called the unilateral z transform and it works a little bit differently than the first case discussed here. We describe it as:
Let’s discuss the whole statement in detail but prior to starting, recall in your mind the definition of discrete-time signals. We know that:
“A discrete-time signal is one whose value can be measured at discrete intervals." When working with a discrete-time signal, there will be time intervals of n during which you will not have a value. In the representation of DT signals, the form x[n] is used. Discrete signals approximate continuous-time (CT) signals."
Therefore, when talking about the z transform, keep the definition of z transform in your mind to understand what exactly is going on.
Now, look at the statement given above.
We have the discrete-time signal in the time domain represented by x[t].
We applied the z transform to it.
Now, we got the same signal that lies in the z domain and is multiplied with a complex number z having the exponential of the n with a negative sign.
Do not worry about the value of n all the time. The summation sign indicates that the value of n starts from negative infinity (or zero in unilateral z transform) to positive infinity, and in this way, we found the values of the series. (This will be much clearer when we discuss the procedure).
Here z is a complex number that is described with the help of this equation:
x(n)⟷X(Z)
The whole discrete time signal is converted into another format with the z transform as a base,
The region of convergence, or simply ROC, is an important term that is used to describe the range of z in the z transform. As we have said, z is a complex number and its range, therefore, has different types of properties.
No. of poles: In z transform, where x[z] is always finite, there are no poles. (We’ll define them in a later section). The ROC of the z transform does not contain any poles.
When talking about a right-sided signal, the region of convergence is always outside the z-plane circle.
When talking about a left-sided signal, the region of convergence is always inside the z-plane circle.
If we have the signal on both sides, then the region of ROC is in the form of a ring inside the circle.
To have a stable form, the region of convergence has a unit value.
There are different cases in the z transform that if we start to describe, will be more confusing and time taking than other transforms. So, we’ll discuss a general format of z transform, and after practice, you will learn the procedure effectively.
Thoroughly examine the question.
Use the formula of the z transform given above.
Put z into the denominator as it has negative power. Doing so will convert the negative power into a positive.
Make sure you take the common values out of the sequence.
Put the value of n as 0, 1, 2, 3, 4, and so on to get the series.
Solve the equation.
It is the most basic and simple description, but the z transform is not that simple. Instead of solving the long calculations, why not use MATLAB for practical implementation? If you have your own course instructor at university, you must have the idea of solving the procedure by hand.
In MATLAB, the z transform is as simple as the previous transform was. Therefore, we are emphasizing the usage of MATLAB at every step. Note that if you want to have a detailed procedure to perform the functions theoretically, you can find your instructors. But from the performance point of view, you should go to MATLAB to confirm your answers all the time. Here is a simple example of an equation that also shows some little details.
Code:
syms n;
f=(2*n+5)/3
disp('x[n]=')
disp(f)
ans=ztrans(f)
disp('z[n]')
disp(F)
Output:
Here, you can see we have used the pre-defined function of z transform given as:
ztrans(x)
With the help of the z transform, you can solve any equation or expression that you want.
Notice that we have used a display function in the code. You must know that z transform can also be done in MATLAB without using the function.
The display function is used to label the numerical output. It does the same work as the xlabel and ylabel in the graphical window of MATLAB. Moreover, this function is also used to call the value that we have specified before using it and to display the results directly. The syntax of the display function is
disp(x)
disp(‘x’)
Where,
To display the string value, we use inverted commas around the value.
To call the value of x, we simply use it as it is.
Never use this function with a capital D or any other change in the spelling, otherwise, you will get the error.
Have a look at another example of the z transform in which we added two trigonometric functions and found their z transform.
Code:
syms n;
f=sin(2*n)
ans=ztrans(f)
g=cos(3*3.14*n)
ans=ztrans(g)
Output:
When you study this particular topic of z transform, you will hear some terms named as zeros and poles. These are the simple topics while learning z transform and usually, are used in the numerical problem. Consider the following equation:
Zeros: while solving the equation with the fraction, the numerator contains the M roots corresponding to the zeros. In the equation given above, q represents the zeros.
Poles: When you are solving the fractional equation by z transform, the N roots in the denominator are called the poles. Here, these are represented with the letter p.
While solving the z transform, we make a circular representation to solve the equation, just like we did while we were learning ROC. Poles are represented at the y-axis, and zeros are represented at the x-axis.
As you can guess from the name, the inverse z transform is used to convert the results of the z transform into the form before the z transform. There are different methods through which the calculations of the z transform are inverted from an equation.
Long division
The partial fraction method of inverse z transforms
Residue method
Power series of inverse z transform
This method is applicable when:
There is a ratio of two polynomials
The polynomials can not be factorized
To apply inverse z transform with this method, the division process of numerator with denominator is carried out. The resultant equation is then passed through the procedure of inverse z transform and we get the results. It is a complex method.
This is the method that involves the rules and procedure of partial fraction (we have received it in the previous lecture) and after that, the inverse z transform is applied.
There are different names for this method including the inversion integration method and contour integral method. For this method, we have to follow the equation given below:
The inverse z transform is obtained by summing up all the residues of this equation from the poles point of view.
In the end, this is the simplest and easiest way to find the z transform. In this method, the equation is expanded and we get the series of ascending powers. After that, the coefficient of z^-n is the required result.
To apply the inverse z transform in MATLAB, we use the following formula:
iztrans(x)
For convenience, we have put the process of z transform and the inverse in the same code.
Code:
syms n;
f=sin(2*n)
F=ztrans(f)
G=iztrans(F)
Output:
We have started the discussion of another transform named the z transform that is somehow similar to the Laplace transform that we have learned in the previous sessions. Z transform is a useful mathematical tool and we studied the ROC, procedure, and the inverse method of z transform. We also saw some examples in MATLAB. In the next lecture, we are going to learn some other basic information on the same topic.
Welcome to the next tutorial of our Raspberry Pi programming course. Our previous tutorial taught us to how to print from a Raspberry pi. We also discussed some libraries to create a print server in our raspberry pi. We will learn how to take screenshots on Raspberry Pi using a few different methods in this lesson. We will also look at how to take snapshots on our Raspberry Pi using SSH remotely.
| Where To Buy? | ||||
|---|---|---|---|---|
| No. | Components | Distributor | Link To Buy | |
| 1 | Breadboard | Amazon | Buy Now | |
| 2 | Jumper Wires | Amazon | Buy Now | |
| 3 | PIR Sensor | Amazon | Buy Now | |
| 4 | Raspberry Pi 4 | Amazon | Buy Now | |
This article will assist you when working with projects that require snapshots for documenting your work, sharing, or generating tutorials.
Screenshots are said to be the essential items on the internet today. And if you have seen these screenshots in tutorial videos or even used them in regular communication, you're already aware of how effective screenshots can be. They are quickly becoming a key internet currency for more efficient communication. Knowing how and when to utilize the correct ones will help you stand out from the crowd.
In this case, we'll employ Scrot, a software program, to help with the PrintScreen procedure. This fantastic software program allows you to take screenshots using commands, shortcut keys, and enabled shortcuts.
Scrot is already installed by default in the latest release of the Raspbian Operating system. In case you already have Scrot, you may skip this installation process. If you're not sure whether it's already installed, use the command below inside a pi Terminal window.
If your Pi returns a "command not found" error, you must install it. Use the following command line to accomplish this:
After installing it, you may test its functionality by using the scrot instruction again. If no errors occur, you are set to go on.
Capturing a snapshot on a Raspberry Pi isn't difficult, especially if Scrot is installed. Here are a handful of options for completing the work.
If you have the Scrot installed on your Pi successfully, your default hotkey for taking screenshots will be the Print Screen key.
You can try this quickly by pressing the Print Screen button and checking the /home/pi directory. If you find the screenshots taken, your keyboard hotkey (keyboard shortcut) is working correctly.
In addition, screenshots and print screen pictures will be stored with the suffix _scrot attached to the end of their filename. For instance,
This is easy as pie! Execute the following command on your Pi to snap a screenshot:
That is all. It is that easy.
The following approach will not work unless you have the navigation closed and have to snap a screenshot without the menu. To get a perfect snapshot with no menu, you must wait a few seconds after taking the picture. You may then close your menu and allow the Scrot to initiate the image capture.
To capture in this manner, send the following command to postpone the operation for five seconds.
Other Scrot settings are as follows:
You might need to give the images a unique name and directory on occasion. Add the correct root directory, followed by the individual title and filename extension, exactly after scrot.
For instance, if you prefer to assign the title raspberryexpert to it and store it in the downloads directory, do the following command:
Remember that the extension should always follow the file name .png.
If the capture command isn't already mapped as a hotkey, you'll have to map it by altering your Pi's config file, and it'll come in handy.
It would be best if you defined a hotkey inside the lxde-pi-rc.xml script to use it. To proceed, use this syntax to open the script.
We'll briefly demonstrate how to add the snapshot hotkey to the XML script. It would be best to locate the <keyboard> section and put the following lines directly below it.
We will map the scrot function to the snapshot hotkeys on the keyboard by typing the above lines.
Save the script by hitting CTRL X, Yes, and afterward ENTER key when you've successfully added those lines.
Enter the command below to identify the new changes made.
You may discover that taking snapshots on the raspberry is impractical in some situations. You'll need to use SSH to take the image here.
When dealing with Ssh, you must first activate it, as is customary. You may get more information about this in our previous tutorials.
Log in with the command below after you have enabled SSH:
Now use the command below to snap an image.
If you've previously installed the Scrot, skip line 2.
Using the command below, you can snap as many snapshots as you like using varying names and afterward transferring them over to your desktop:
Remember to change the syntax to reflect the correct username and Ip.
you can snap a screenshot and save it immediately to your Linux PC. However, if you regularly have to take snapshots, inputting the passcode each time you access the Rpi via SSH will be a tedious chore. So you can use publicly or privately keys to configure no passcode ssh in raspberry pi.
To proceed, use the following command to install maim on raspberry pi.
Return to your computer and use the command below to take a snapshot.
We're utilizing the maim instead of other approaches since it's a more elegant method. It sends the image to stdout, allowing us to save it to our laptop via a simple URL redirect.
Raspi2png is a screenshot software that you may use to take a screenshot. Use the code below for downloading and installing the scripts.
After that, please place it in the /usr/local/bin directory.
Enter the following command to capture a screenshot.
Ensure to use your actual folder name rather than <directory_name> used.
Because we are using a GUI, this solution is relatively simple and easy to implement.
First, use the following command to download the GNOME Snapshot tool.
After it has been installed, go to the Raspberry navbar, select the menu, select Accessories, and finally, Screenshot.
This opens the GNOME Picture window, where you can find three different taking options, as seen below.
Choose the appropriate capture method and select Capture Image. If you pick the third choice, you will have to use a mouse to choose the location you wish to snip. If you use this option, you will not need a picture editor to resize the snapshot image. The first choice will record the entire screen, while the second will snip the active window.
GNOME gives you two alternatives once you capture a screen. The first is to save the snapshot, and the other is to copy it to the clipboard. So select it based on your requirements.
It all begins with a simple screenshot. You don't need any additional programs or software to capture a basic screenshot. At this moment, this feature is built into almost all Raspberry Pi versions and Windows, Mac PCs, and cellphones.
It is the process of capturing all or a part of the active screen and converting it to a picture or video.
While it may appear the same thing as a screenshot and a screen capture, they are not the same. A screenshot is simply a static picture. A desktop window capture is a process of collecting something on the screen, such as photographs or films.
Assume you wish to save a whole spreadsheet. It's becoming a little more complicated now.
Generally, you would be able to record whatever is on your window. Still, in case you need to snip anything beyond that, such as broad, horizontal spreadsheets or indefinitely lengthy website pages, you'll need to get a screen capture application designed for that purpose. Snagit includes Scrolling snapshot and Panorama Capture capabilities to snap all of the material you need in a single picture rather than stitching together many images.
This is a GIF file containing a moving image. An animated succession of picture frames is exhibited.
While gif Images aren't limited to screen material, they may be a proper (and underappreciated) method to express what's on your display.
Instead of capturing multiple pictures to demonstrate a process to a person, you may create a single animated Version of what is going on on your computer. These animations have small file sizes, and they play automatically, making them quick and simple to publish on websites and in documents.
This is making a video out of screen material to educate a program or sell a product by displaying functionality.
If you want to go further than a simple snapshot or even gif Animation, they are a good option. If you have ever looked for help with a software program, you have come across a screencast.
They display your screen and generally contain some commentary to make you understand what you are viewing.
Screencasts can range from polished movies used among professional educators to fast recordings showing a coworker how to file a ticket to Information technology. The concept is all the same.
Using screenshots to communicate removes the guesswork from graphical presentations and saves time.
The snapshot tool is ideal for capturing screenshots of graphical designs, new websites, or social media posts pending approval.
This is a must-have tool for anybody working in Information Technology, human resource, or supervisors training new workers. Choose screenshots over lengthy emails, or print screen pictures with instructions. A snapshot may save you a lot of time and improve team communication.
Furthermore, by preserving the snapshot in Screencast-O-Matic, your staff will be able to retrieve your directions at any time via a shareable link.
To avoid confusion, utilize screen captures to show. IT supervisors, for instance, can utilize images to teach their colleagues where to obtain computer upgrades. Take a snapshot of the system icon on your desktop, then use the Screen capture Editor to convert your screen capture into a graphical how-to instruction.
Any image editing tool may be used to improve pictures. You may use the highlighting tool to draw attention to the location of the icons.
Everybody has encountered computer difficulties. However, if you can't articulate exactly what has happened, diagnosing the problem afterward will be challenging. It's simple to capture a snapshot of the issue.
This is useful when talking with customer service representatives. Rather than discussing the issue, email them an image to help them see it. Publish your image immediately to Screencast and obtain a URL to share it. Sharing photos might help you get help quickly.
It can also help customer support personnel and their interactions with users. They may assist consumers more quickly by sending screenshots or photographs to assist them in resolving difficulties.
Snapshots are a simple method for social media administrators to categorize, emphasize, or record a specific moment. Pictures are an easy method to keep track of shifting stats or troublesome followers. It might be challenging to track down subscribers who breach social network regulations. Comments and users are frequently lost in ever-expanding discussions.
Take a snapshot of the problem to document it. Save this image as a file or store it in the screenshots folder of Screencast. Even if people remove their remarks, you will have proof of inappropriate activity.
This tutorial taught us how to take screenshots from a Raspberry Pi using different methods. We also went through how to remotely take snapshots on our Pi using SSH and discussed some of the benefits of using the screenshot tool. However, In the following tutorial, we will learn how to use a raspberry pi as a webserver.
Keywords
ESP32, IoT, Temperature sensor, Humidity sensor, Pressure sensor, Altitude sensor, Arduino IDE, ThingSpeak.
| Where To Buy? | ||||
|---|---|---|---|---|
| No. | Components | Distributor | Link To Buy | |
| 1 | ESP32 | Amazon | Buy Now | |
The evolving generation of wireless technology has made human life a lot easier. Where everything is online and automatic we can easily monitor multiple things virtually from anywhere in the world. The WSN (wireless sensor networks) and Internet of things or IoT play an important role in implementing and accessing these wireless technologies. Smart homes, smart cities and smart weather monitoring systems are examples of such technologies where things are quite simpler or easier.
In this web-server based weather monitoring system, the weather data (from the surrounding environment or of a particular location) like temperature, humidity, pressure etc. is measured with the help of some sensors and then the collected data will be stored on a server after being processed by a microcontroller. Our daily activities are inseparable from weather conditions and various environmental factors. The real-time data collected can be used in research and analysis and the results can be helpful in human life and for improving environmental conditions as well.
The Internet of Things is a system made up of multiple inter-related computing devices. The main factor ‘things’ in IoT is designated to a component that is capable of communicating data over a network (IoT), the thing could be animals, a digital machine, a sensor, a human being etc. Each component of the Internet of Things network is given an individual or a distinct identity and the ability to communicate data or information over a wireless network that is too without the intervention of a human or a computer [8].
An interface medium capable of collecting, controlling, and communicating data among transmitter and recipient electronic equipment or servers is required to build the IoT network[9].
The ESP32 microcontroller series was developed by Espressif Systems. This module (the ESP32) includes a 2.4GHz Wi-Fi chip, memory, a 32-bit Tensilica microcontroller, an antenna, peripheral interfacing abilities, power management modules, and more. This ESP32 module is excellent for the Internet of things because of all of its technological and infrastructural aspects [10].
DHT11 and BMP280 sensors are used to collect the data from their surrounding environment and then communicate the data to the ESP32 module over a particular protocol [11].
The application of this weather monitoring system can also play an important role in the field of agriculture[12 ] to increase productivity, research application, and reducing manpower (by reducing the need to manually monitor the field status). Sometimes in a particular agricultural zone that is hazardous for a human beings, it is quite difficult to manually (offline) monitor the environment or weather conditions. In such cases, this web server based or online weather monitoring system can be of great importance.
Fig. 1
The list and quantity of the components required to implement the web server based weather monitoring system are shown in Table1.
Table: 1
Fig. 2 DHT11 sensor
DHT11 sensor (or temperature and humidity sensor) is a sensor module used to measure humidity and temperature from its surrounding. This sensor module is responsible for monitoring the ambient temperature and humidity of a given area. An NTC (negative temperature co-efficient) temperature sensor and a resistive type humidity sensor make up the sensor. An 8-bit microcontroller is also included. The microcontroller performs ADC (analogue to digital conversion) and outputs a digital signal via the single wire protocol [13].
Some of the technical specifications of the DHT11 sensor are:
Table:2 DHT11 technical specifications
DHT11 sensors can also be used to create a wired sensor system with up to 20 meters of cable.
To measure temperature and humidity, two DHT modules (DHT11 and DHT22) are available on the market. Both modules serve the same purpose, but they have different specifications. The DHT22 sensor, for example, has a wider range of temperature and humidity sensitivity. However, DHT22 is more expensive than DHT11. As a result, you can choose to use any of the modules as per your needs.
Table.3 Interfacing DHT11 with ESP32
Another sensor we are using is the BMP280. The BMP280, also known as the barometric pressure sensor, is a temperature, pressure, and altitude sensor. This sensor's small size and low power consumption make it suitable for mobile applications, GPS modules, and battery-powered devices, among other things[15].
The Bosch BMP280 is based on Bosch's validated ‘Piezo-resistive pressure sensor technology’, which features high accuracy, long-term stability, linearity, and EMC robustness.
The barometric pressure sensor (280) is the successor to the BMP180 sensor, and it is mostly preferred in all areas where precise temperature and pressure measurements are required.
Fig.3 BMP280 Sensor
Fitness, indoor navigation, and GPS refinement are all new technologies which require relative accuracy, and the BMP280 is ideal for them. This module is preferred over the other available modules for temperature records or measurement because of its low TCO (Temperature coefficient of Offset).
The temperature measured with the BMP280 sensor is more accurate than the DHT11 sensor. BMP80 provides a 0.01°C accuracy rate.
Some technical specifications of the BMP280 sensor are:
Table:4 BMP280 Technical specifications
A web server is a place where one can store data online and can access that data at any time and from anywhere in the world [16]. A real-time data is created with the help of a web-server. There are various web services available to store real-time data for research and analysis like AWS (Amazon Web Service), Azure, Firebase etc.
We are using the ThinSpeak web service provided by MathWorks which allows us to send sensor readings/data to the cloud. The ThingSpeak is an open source data platform for the Internet of Things (IoT) applications. We can also visualize and act on or access the data (calculate the data) sent to the ThingSpeak server from ESP32. Two different types of channels are available to store data on the ThingSpeak server namely ‘Public Channel’ and ‘Private Channel’ and one can use either of the available channels to store and display data [17].
ThingSpeak is frequently used for IoT prototyping and proof-of-concept systems that require analytics[18].
We need to give instructions to our ESP32 module so that it can interface, read data from DHT11 and BMP280 sensors and then finally publish the collected data to the ThingSpeak server. Arduino IDE is an integrated development environment used to write, compile and debug the program for the ESP32 module[19].
Fig. Arduino IDE
The process flow of our weather monitoring system is shown below in Chart 1. The process starts with the initialization of ESP32 module which is acting as an interface medium between the sensor modules and the web-server. The ESP32 wi-fi module is continuously searching for the network credentials as per the instruction provided. After connecting to the internet the sensor modules will be initialized and the real-time data [22] collected from the surrounding environment will be pushed to the ThingSpeak web server[23].
Flow Chart: 1
The results observed from the implemented weather monitoring system are shown below. We observed four different environmental conditions which include temperature, humidity, pressure and altitude. The sensor data collected by ESP32 from DHT11 and BMP280 sensors is published to the ThingSpeak web server. On ThingSpeak we have created a channel that contains four fields to store four different environmental factors temperature, humidity, pressure and altitude.
Fig. Hardware
In fig. 4 we can see the ‘Field 1’ which is containing the temperature readings published or communicated from the ESP32 module and saved on the ThingSpeak server.
Similarly, fields 2, 3, and 4 are displaying the humidity, pressure and altitude respectively.
Fig. 4 Temperature (°C)
Fig. 5 Humidity
Fig. 6 Pressure (hPa)
Fig. 7 Altitude
Each factor is monitored at different intervals of time to observe the variations in various environmental factors. From table 5 we can see the various environmental factors and their values at different time intervals for the approximate duration of 24hrs.
Table 5 Variations in weather conditions
We observed the weather conditions (that includes temperature, humidity, pressure and altitude) with our “Web-server based weather monitoring system using ESP32”. The observed real time data is stored on the ThingSpeak server which can be accessed globally. The different values of each (mentioned earlier) environmental factor at different intervals in time are also observed (given in table 5) and the observed result clearly shows the changes in the weather conditions for a full day cycle. Hence, we have successfully implemented and tested the web server based weather monitoring system with ESP32 and ThingSpeak web server.
Internet of Things is a system of multiple inter-related computing devices. The factor ‘thing’ in IoT is designated to an entity capable of communicating data over a network (IOT), which can be a digital machine, sensor, human being, animals etc. Each component that is included in IoT network is assigned with an unique identity called UID and the ability to communicate data over IoT network without any external human or computer intervention.
Hello readers, I hope you all are doing great. In our previous tutorial, we discussed how to upload data to Firebase Real-time Database using ESP32. In this tutorial, we will learn how to read the data stored on the Firebase Database with ESP32.
We can access the data stored in Firebase database from anywhere in the world, which makes this preferable in IoT applications.
| Where To Buy? | ||||
|---|---|---|---|---|
| No. | Components | Distributor | Link To Buy | |
| 1 | ESP32 | Amazon | Buy Now | |
In our previous tutorial, we learnt how to upload an integer value (for demonstration) to Firebase real-time database. So, in this tutorial we will learn how to fetch or receive those integer values from Firebase database.
To access real-time data, we are using two ESP boards where one is used to upload/store the real-time data to the Firebase database and another to read the data stored on the firebase.
Although, it is not required to use two ESP boards, we can also access the previously saved data on the Firebase database with only a single ESP32/ESP8266 board.
We can use the same code for both ESP32 and ESP8266 but we need to make some changes like some of the libraries will be different for ESP8266 and the selection of ESP8266 development board while uploading the code with Arduino IDE.
Fig. 1 Reading data from firebase
Google's Firebase real-time database is a development platform that includes a number of services for managing and authenticating data.
Firebase is a mobile and web app development platform (that also works well with Android APIs) that includes features such as Firebase Cloud, real-time data, and Firebase authentication, among others.
According to Firebase's official documentation (https://firebase.google.com/docs/database), when a user creates a cross-platform application using JavaScript SDKs for Android or Apple, all clients share a single database.
Fig. 1 Firebase Real-time database and ESP32
The following are the main features of the Firebase Real-time database:
The Internet of Things, also known as IoT, is the interconnection of physical objects or devices with sensors and software accessing capabilities in order to communicate data or information over the internet.
We need an interface medium that can fetch, control, and communicate data between sender and receiver electronics devices or servers in order to build an IoT network.
The Firebase real-time database gives you a place to store data from sensors on your level device. With Android APIs, Firebase performs admirably.
Firebase is especially useful for storing data from sensors and syncing it between users in real-time in data-intensive Internet of things (IoT) applications. For the sake of simplicity and clarity, we can say that it is a Google cloud service for real-time collaborative apps.
We are using Arduino IDE to compile and upload code into the ESP32 module. You must have ESP32 board manager installed on your Arduino IDE to program the ESP32 module. To know more about Arduino IDE and how to use it, follow our previous tutorial i.e., on ESP32 programming series. The link is given below:
https://www.theengineeringprojects.com/2021/11/introduction-to-esp32-programming-series.html
Fig. 2 manage libraries
Fig. 3 Install Firebase ESP Client Library
We have already posted a tutorial on our website on getting started with Firebase real-time database and how to post or upload data to Firebase database from ESP32. Where we discussed, how to create a project on Firebase real-time database, authentication, how to access the API key and project URL etc.
So now we do not need to create a new project, we are using the same project and hence same API key and project URL to read or download the data from Firebase real-time database.
Fig. 4 Project Setting
Fig. 5 Project API key
Fig. 6 Project URL
//--add necessary header files
#include <WiFi.h>
#include <Firebase_ESP_Client.h>
#include "addons/TokenHelper.h" //Provide the token generation process info.
#include "addons/RTDBHelper.h" //Provide the real-time database payload printing info and other helper functions.
// Insert your network credentials
#define WIFI_SSID "ssid"
#define WIFI_PASSWORD "password"
// Insert Firebase project API Key
#define API_KEY "replace this with your project API key"
// ----Insert real-time database URL
#define DATABASE_URL "replace this with your project URL"
//Define Firebase Data object
FirebaseData fbdo;
FirebaseAuth auth;
FirebaseConfig config;
unsigned long sendDataPrevMillis = 0;
int read_data;
bool signupSuccess = false;
void setup() {
Serial.begin(115200);
WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
Serial.print("Connecting to Wi-Fi");
while (WiFi.status() != WL_CONNECTED) {
Serial.print(".");
delay(200);
}
Serial.println();
Serial.print("Connected to... ");
Serial.println(WiFi.localIP());
Serial.println();
// Assigning the project API key
config.api_key = API_KEY;
//Assign the project URL
config.database_url = DATABASE_URL;
/// check signup statue
if (Firebase.signUp(&config, &auth, "", "")) {
Serial.println("ok");
signupSuccess = true;
}
else {
Serial.printf("%s\n", config.signer.signupError.message.c_str());
}
// Assign the callback function for token generation task
config.token_status_callback = tokenStatusCallback;
Firebase.begin(&config, &auth);
Firebase.reconnectWiFi(true);
}
void loop()
{
if (Firebase.ready() && signupSuccess && (millis() -
sendDataPrevMillis > 8000 || sendDataPrevMillis == 0))
{
sendDataPrevMillis = millis();
if (Firebase.RTDB.getInt(&fbdo, "/test/int"))
{
if (fbdo.dataType() == "int")
{
read_data = fbdo.intData();
Serial.print("Data received: ");
Serial.println(read_data); //print the data received from the Firebase database
}
}
else
{
Serial.println(fbdo.errorReason()); //print he error (if any)
}
}
}
Fig. 7 Header files
Fig. 8 Helper libraries
Fig. 9 Insert API key
Fig. 10 RTDB URL
Fig. 11 Firebase Data Objects
Fig. 12 Enter Network credentials
Fig. 13 Initialize wifi module
Fig. 14 Fetch/obtain the IP address
Fig. 15 configuring API key
Fig. 16 configuring database URL
Fig. 17 sign up status
Fig. 18
Fig. 19 Fetch data from Firebase RTDB
Fig. 20
Fig. 21 Select development board and COM port
Fig. 22 Data sent Vs Data Received
This concludes the tutorial. I hope you found this of some help and also hope to see you soon with a new tutorial on ESP32.
Hello readers, I hope you all are doing great. In this tutorial, we will learn how to access Firebase (a real-time database) to store and read values or data with ESP32.
It is Google’s mobile application development platform that can be used to can access, monitor and control ESP32 from anywhere in the world with its (firebase) real-time database.
| Where To Buy? | ||||
|---|---|---|---|---|
| No. | Components | Distributor | Link To Buy | |
| 1 | ESP32 | Amazon | Buy Now | |
Firebase real-time database is a development platform provided by Google which included multiple services to manage and authenticate data.
Firebase is basically a mobile and web app development platform I as works great with Android APIs) that includes features like firebase cloud, real-time data and Firebase authentication etc.
As per Firebase’s official documentation (https://firebase.google.com/docs/database), whenever a user creates a cross-platform application like with Android, or Apple, JavaScript SDKs, all the clients share a single.
Fig. 1 Firebase Real-time database and ESP32
The main features of the Firebase Real-time database are:
The IoT or Internet of Things is the interconnection of physical objects or devices with sensors and software accessing capabilities to communicate data or information over the internet.
To build an IoT network, we need an interface medium that can fetch, control, and communicate data between sender and receiver electronics devices or servers.
Firebase real-time database provides a platform to store data collected from sensors at the level device. Firebase works great with Android APIs.
Firebase is particularly useful in data-intensive Internet of things (IoT) applications to store from sensors and synch that data between users in real-time. For simplicity or better understanding we can say that it is a cloud service provided by Google for real-time collaborative apps.
The steps involved in creating a Firebase project are:
Fig. 2 Get started
Fig. 3 Create a project
Fig. 4 project name
Fig. 5 Enabling Google Analytics
Fig. 6 Project Created successfully
As per the official firebase documentation at: https://firebase.google.com/docs/auth , the identity of a user is required by most online services or mobile applications or we can say , it handles authentication process and logging in (in this tutorial, the ESP32). Getting to know the identity of a user enables an application to save user data securely in the cloud and provide a consistent personalized service across all of the customer's devices (android phones, computers, applications etc).
Fig. 7 Authentication
Fig. 8 Select authentication method
Next thing is creating a real-time database for the project.
Fig. 9 Real-time database
Fig. 10 Creating database
Fig. 11
Fig. 12 select location
Fig. 13 Accessing project API key
We are using Arduino IDE to compile and upload code into the ESP32 module. You must have the ESP32 board manager installed on your Arduino IDE to program the ESP32 module. To know more about Arduino IDE and how to use it, follow our previous tutorial i.e., on ESP32 programming series. The link is given below:
https://www.theengineeringprojects.com/2021/11/introduction-to-esp32-programming-series.html
Steps to add the necessary libraries in Arduino IDE:
Fig. 14 manage libraries
Fig. 15 Install Firebase ESP Client Library
//--add necessary header files
#include <WiFi.h>
#include <Firebase_ESP_Client.h>
#include "addons/TokenHelper.h" //Provide the token generation process info.
#include "addons/RTDBHelper.h" //Provide the real-time database payload printing info and other helper functions.
// Insert your network credentials
#define WIFI_SSID "replace this with your netwrok SSID"
#define WIFI_PASSWORD "replace this with your wi-fi password"
// Insert Firebase project API Key
#define API_KEY "replace this with your API key"
// ----Insert real-time database URL
#define DATABASE_URL "replace this with your project URL"
//----Define Firebase Data object
FirebaseData fbdo;
FirebaseAuth auth;
FirebaseConfig config;
int value = 10;
bool signupSuccess = false;
unsigned long sendDataPrevMillis = 0;
void setup()
{
Serial.begin(115200);
WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
Serial.print("Connecting to Wi-Fi");
while (WiFi.status() != WL_CONNECTED){
Serial.print(".");
delay(100);
}
Serial.println();
Serial.print("Connected with IP: ");
Serial.println(WiFi.localIP() );
Serial.println();
// Assign the api key ( required)
config.api_key = API_KEY;
// Assign the RTDB URL ( required)
config.database_url = DATABASE_URL;
// Sign up status
if (Firebase.signUp(&config, &auth, "", ""))
{
Serial.println("ok");
signupSuccess = true;
}
else{
Serial.printf("%s\n", config.signer.signupError.message.c_str());
}
/* Assign the callback function for the long running token generation task */
config.token_status_callback = tokenStatusCallback; // see addons/TokenHelper.h
Firebase.begin(&config, & auth);
Firebase.reconnectWiFi( true);
}
void loop()
{
if (Firebase.ready() && signupSuccess && (millis() - sendDataPrevMillis >
10000 || sendDataPrevMillis == 0))
{
sendDataPrevMillis = millis();
if (Firebase.RTDB.setInt(&fbdo, "test/int", value))
{
Serial.println("PASSED");
Serial.println("PATH: " + fbdo.dataPath());
Serial.println("TYPE: " + fbdo.dataType());
}
else
{
Serial.println("FAILED");
Serial.println("REASON: " + fbdo.errorReason());
}
value++;
}
}
Before uploading the code in ESP32 board there are some changes you need to make which includes:
Fig. 16 Header files
Fig. 17 Helper libraries
Fig. 18 Insert API key
Fig. 19 RTDB URL
Fig. 20 Firebase Data Objects
Fig. 21 Enter Network credentials
Fig. 22 variable declaration
Fig. 23 Initialize wifi module
Fig. 24 Fetch/obtain the IP address
Fig. 25 configuring API key
Fig. 26 configuring database URL
Fig. 27 sign up status
Fig. 28
Fig. 29 Loop() function
Fig. 30 Select development board and COM port
Fig. 31 Result 1
Fig. 32 Result 2
This concludes the tutorial. I hope you found this of some help and also hope to see you soon with a new tutorial on ESP32.
Hello readers, I hope you all are doing great. In this tutorial, we will learn how to interface the BMP280 sensor with the ES32 module to get temperature, pressure and altitude readings. Later, in this tutorial, we will also discuss how to upload these sensor readings to a web server.
| Where To Buy? | ||||
|---|---|---|---|---|
| No. | Components | Distributor | Link To Buy | |
| 1 | ESP32 | Amazon | Buy Now | |
BMP280 or Barometric pressure sensor is a module used to measure temperature pressure and altitude. The small size and low power consumption feature of this sensor makes it feasible for battery-powered devices, GPS modules and mobile applications etc.
Fig. 1 BMP280 Sensor
The BMP280 is the product of BOSCH which is based on Bosch’s proven Piezo-resistive pressure sensor technology featured with high accuracy, long term stability, linearity and high EMC robustness.
BMP280 is the successor of the BMP180 sensor and offers high performance in all the areas that require precise temperature and pressure measurements.
Emerging applications like fitness, indoor navigation, GPS refinement requires relative accuracy and BMP280 is perfect for such applications. Very low TCO (Temperature coefficient of Offset ) makes this module preferable over other available modules for temperature measurements.
We can also use a DHT11/DHT22 sensor for temperature and humidity measurements but the BMP280 sensor provides better accuracy (i.e., 0.01°C) than DHT sensors.
There are two methods of interfacing BMP280 sensor with ESP32 module:
In the bMP280 Sensor module, there are six interfacing pins including VCC and GND.
Fig. Interfacing BMP280 and ESP32
We are using the I2C protocol for interfacing the two (ESP and BMP280) so only SCL and SDA pins will be used with power pins for interfacing. The SDO and CSB pins will be used only if you are using the SPI protocol for interfacing.
Table 1
We are using Arduino IDE to compile and upload code into the ESP32 module. You must have ESP32 board manager installed on your Arduino IDE to program the ESP32 module. To know more about Arduino IDE and how to use it, follow our previous tutorial i.e., on ESP32 programming series. The link is given below:
https://www.theengineeringprojects.com/2021/11/introduction-to-esp32-programming-series.html
Steps to add the necessary libraries in Arduino IDE:
Fig. 2 manage libraries
Fig. 3 Install library
#include <Wire.h>
void setup()
{
Wire.begin();
Serial.begin(115200);
Serial.println("\nI2C Scanner");
}
void loop()
{
byte error, address;
int nDevices;
Serial.println("Scanning...");
nDevices = 0;
for(address = 1; address < 127; address++ )
{
Wire.beginTransmission(address);
error = Wire.endTransmission();
if (error == 0)
{
Serial.print("I2C device found at address 0x");
if (address<16)
{
Serial.print("0");
}
Serial.println(address,HEX);
nDevices++;
}
else if (error==4)
{
Serial.print("Unknow error at address 0x");
if (address<16) {
Serial.print("0");
}
Serial.println(address,HEX);
}
}
if (nDevices == 0) {
Serial.println("No I2C devices found\n");
}
else {
Serial.println("done\n");
}
delay(5000);
}
#include <Wire.h>
#include <Adafruit_BMP280.h>
#define BMP_SDA 21
#define BMP_SCL 22
Adafruit_BMP280 bmp280;
void setup()
{
Serial.begin(115200);
Serial.println("Initializing BMP280");
boolean status = bmp280.begin(0x76);
if (!status)
{
Serial.println("Not connected");
}
}
void loop()
{
float temp = bmp280.readTemperature();
Serial.print("temperature: ");
Serial.print(temp);
Serial.println("*C");
float altitude = bmp280.readAltitude(1011.18);
Serial.print("Altitude: ");
Serial.print(altitude);
Serial.println("m");
float pressure = (bmp280.readPressure()/100);
Serial.print("Pressure: ");
Serial.print(pressure);
Serial.println("hPa");
Serial.println(" ");
delay(1000);
}
Fig. 6
Fig. 7
Fig. 8
Fig. 9
Fig. 10 Select development board and COM port
Fig. 11 Serial monitor output
Most of the industries and organizations these days are shifting to the efficient ways of operating things and the IoT internet of things is one of them.
Internet of Things is a system of multiple inter-related computing devices. The factor ‘thing’ in IoT is designated to an entity capable of communicating data over a network (IOT), which can be a digital machine, sensor, human being, animals etc.
Each component that is included in IoT network is assigned with an unique identity called UID and the ability to communicate data over IoT network without any external human or computer intervention.
Fig. 12 IoT
ThingSpeak is an open data platform for the Internet of Things applications. It is a MathWorks web service that allows users to send sensor readings and data to the cloud. We can also visualize and act on the data (calculate the data) that is sent to ThingSpeak by the devices. The information can be saved in both private and public channels.
ThingSpeak is frequently used for IoT prototyping and proof-of-concept devices that require data analysis.
Downloading and installing the required Library file:
https://github.com/mathworks/thingspeak-arduino
Fig. 13 Adding ThingSpeak library
To check whether the library is successfully added or not:
Fig. 14
Fig, 15 Arduino IDE Library manager
Fig. 16 Getting started for free
Fig. 17 Create new account
Fig. 18 MathWorks Sign in
Fig. 19 New Channel
Fig. 20 Creating channel and respective fields
Fig. 21 save the channel
Fig. 22 Field Chart Edit
// ------style guard ----
#ifdef __cplusplus
extern "C"
{
#endif
uint8_t temprature_sens_read();
#ifdef __cplusplus
}
#endif
uint8_t temprature_sens_read();
// ------header files----
#include <WiFi.h>
#include "ThingSpeak.h"
#include <Wire.h>
#include <Adafruit_BMP280.h>
#define BMP_SDA 21
#define BMP_SCL 22
Adafruit_BMP280 bmp280;
// -----netwrok credentials
const char* ssid = "public"; // your network SSID (name)
const char* password = "ESP32@123"; // your network password
WiFiClient client;
// -----ThingSpeak channel details
unsigned long myChannelNumber = 4;
const char * myWriteAPIKey = "9R3JZEVBG73YE8BY";
// ----- Timer variables
unsigned long lastTime = 0;
unsigned long timerDelay = 1000;
void setup()
{
Serial.begin(115200); // Initialize serial
Serial.println("Initializing BMP280");
boolean status = bmp280.begin(0x76);
if (!status)
{
Serial.println("Not connected");
}
//Initialize Wi-Fi
WiFi.begin(ssid, password);
Serial.print("Connecting to Wi-Fi");
while (WiFi.status() != WL_CONNECTED)
{
Serial.print(".");
delay(100);
}
Serial.println();
Serial.print("Connected with IP: ");
Serial.println(WiFi.localIP());
Serial.println();
// Initialize ThingSpeak
ThingSpeak.begin(client);
}
void loop()
{
if ((millis() - lastTime) > timerDelay )
{
float temp = bmp280.readTemperature(); //temperature measurement
Serial.print("temperature: ");
Serial.print(temp);
Serial.println("*C");
float altitude = bmp280.readAltitude(1011.18); //altitude measurement
Serial.print("Altitude: ");
Serial.print(altitude);
Serial.println("m");
float pressure = (bmp280.readPressure()/100); //pressure measurement
Serial.print("Pressure: ");
Serial.print(pressure);
Serial.println("hPa");
Serial.println(" ");
ThingSpeak.setField(1, temp );
ThingSpeak.setField(2, altitude);
ThingSpeak.setField(3, pressure);
// Write to ThingSpeak. There are up to 8 fields in a channel, allowing you to store up to 8 different
// pieces of information in a channel. Here, we write to field 1.
int x = ThingSpeak.writeFields(myChannelNumber,
myWriteAPIKey );
if(x == 200)
{
Serial.println("Channel update successful." );
}
else
{
Serial.println("Problem updating channel. HTTP error code " + String(x) );
}
lastTime = millis();
}
}
We are describing only the ThingSpeak server part as the BMP280 and ESP32 interfacing part has already been discussed in the above code description.
Fig. 23 Style guard
Fig. 24 Libraries
Fig. 25
Fig. 26
Fig. 27
Fig. 28
Fig. 29
Fig. 30
Fig. 31
Fig. 32 Sensor readings
Fig. 33 setting respective Fields
Fig. 34
Fig. 35
Fig. 36 ThingSpeak server
Fig. 37 Sensor readings on the Serial monitor
This concludes the tutorial. I hope you found this of some help and also hope to see you soon with a new tutorial on ESP32.
Hello readers, I hope you all are doing great.
ESP32 is a powerful chip for Internet of Things applications. This tutorial is also based on one of the ESP32 applications in the field of IoT.
| Where To Buy? | ||||
|---|---|---|---|---|
| No. | Components | Distributor | Link To Buy | |
| 1 | ESP32 | Amazon | Buy Now | |
In this tutorial, we will learn how to update LCD display with new data or input using a web server created with ESP32.
Fig. 1
To achieve the target, we will be using an HTML (Hypertext Markup Language) form to provide web input and then update the text displayed on LCD. The values or input received from the webserver will be further stored inside a variable in the code for further use (to display on LCD).
We have already posted a tutorial on LCD (Liquid Crystal Display) interfacing with ESP32. In that tutorial, we demonstrated how to display the hard-coded data (in the ESP32 module) on LCD.
A web server is computer software and hardware that accepts requests and responds to those requests using HTTP (Hypertext transfer protocol) or HTTPS (HTTP Secure) (HTTP is a network protocol for delivering online content to client user agents).
The ESP32 standalone web server is mobile-enabled and can be accessed from any device with a browser on the local network. B. Mobile phones, computers, laptops, tablets. However, all the devices must be connected to the same WiFi network to which the ESP32 is connected.
There are basically two ways to connect the ESP32 to a 16 * 2 LCD display.
Connecting an LCD display without an I2C adapter is cheap, but this method requires more connection cables and is complicated to implement. On the other hand, using an I2C adapter reduces complexity but increases cost. In this tutorial, you will connect the ESP32 directly without using an I2C adapter.
Table: 1
Fig. 2: ESP32 and 16*2 LCD interfacing
For more details on interfacing 16*2 LCD with ESP32, follow our previous tutorial at www.theengineeringprojects.com
We are using Arduino IDE to compile and upload code into ESP32 module. You must have ESP32 board manager installed on your Arduino IDE to program ESP32 module. To know more about Arduino IDE and how to use it, follow our previous tutorial i.e., on ESP32 programming series. The link is given below:
https://www.theengineeringprojects.com/2021/11/introduction-to-esp32-programming-series.html
ESP32 board manager doesn’t come with inbuilt libraries to create an asynchronous web server. So we need to download the library file from external sources and then add into Arduino IDE.
We need to install two library files:
Once you have successfully downloaded the required libraries, next step it to install or add these libraries in Arduino IDE.
To add the libraries in Arduino IDE, go to Sketch >> Include Library >> Add .zip library and then select the downloaded library files.
Fig. 3: adding necessary libraries
#include < WiFi.h >
#include < AsyncTCP.h >
#include < ESPAsyncWebServer.h >
#include < LiquidCrystal.h > // LCD header file
LiquidCrystal lcd (22, 23, 5, 18, 19, 21 );
AsyncWebServer server ( 80 );
// Enter your netwrok credentials
const char* ssid = "replace this with netwrok SSID";
const char* password = "replace this with Password";
const char* PARAM_INPUT_1 = "data_field1";
const char* PARAM_INPUT_2 = "data_field2";
// HTML web page to handle data input fields
const char index_html[] PROGMEM = R"rawliteral(
<!DOCTYPE HTML> <html> <head>
<title> ESP Input Form </title>
<meta name = " viewport" content="width=device-width, initial-scale=1 ">
<style>
html{ font-family: Times New Roman; display: inline-block; text-align: justify;}
</style>
</head> <body>
<form action="/get">
Data_field1: <input type="text" name="data_field1" >
<input type="submit" value="Post ">
</form> <br>
<form action="/get">
Data_field2: <input type="text" name="data_field2">
<input type="submit" value="Post">
</form><br>
</body></html>)rawliteral";
void notFound(AsyncWebServerRequest *request) {
request->send(404, "text/plain", "Not found");
}
void setup() {
Serial.begin(115200);
WiFi.mode(WIFI_STA);
WiFi.begin(ssid, password);
if (WiFi.waitForConnectResult() != WL_CONNECTED) {
Serial.println("WiFi Failed!");
return;
}
Serial.println();
Serial.print("IP Address: ");
Serial.println(WiFi.localIP());
//===set LCD
lcd.begin(16, 2);
lcd.clear();
lcd.setCursor(1,0);
server.onNotFound(notFound);
server.begin();
// Send web page with input fields to client
server.on("/", HTTP_GET, [](AsyncWebServerRequest *request)
{
request->send_P(200, "text/html", index_html);
});
server.on("/get", HTTP_GET, [] (AsyncWebServerRequest *request) {
String inputMessage;
String inputParam;
// GET input1 value
if (request->hasParam(PARAM_INPUT_1))
{
inputMessage = request->getParam(PARAM_INPUT_1)->value();
inputParam = PARAM_INPUT_1;
}
// GET input2 value
else if (request->hasParam(PARAM_INPUT_2))
{
inputMessage = request->getParam(PARAM_INPUT_2)->value();
inputParam = PARAM_INPUT_2;
}
else
{
inputMessage = " No message sent";
inputParam = " none";
}
Serial.println ( inputMessage );
delay( 1000);
lcd.clear();
lcd.print( inputMessage);
request-> send (200, "text/html", " HTTP GET request sent to ESP32("
+ inputParam + "): " + inputMessage +
"<br><a href=\"/\"> Back to Home Page </a>");
});
}
void loop( )
{
}
Fig. 4: Adding header files
Fig. 5: LCD data and control pins
Fig. 6: server port
Fig. 7: Enter Network credentials
Fig. 8
Fig. 9: HTML web page
Fig. 10: HTML form for data input
Fig. 11: Post button.
Fig. 12
Fig. 13: Fetch/obtain the IP adrress
Fig. 14: Set 16*2 LCD
Fig. 15: Initialize the server
Fig. 16: Send web page to client
Fig. 17
Fig. read the input from HTML form
Fig. 18
Fig. 19
Fig. 20
Fig. 21: Select development board and COM port
Fig. 22: web Page
Fig. 23: Enter the Input to ESP32
Fig. 24: Input Updated
Fig. 25: IP address and Web Input on serial monitor.
Fig. 26: String input received from Web server, printed on LCD
This concludes the tutorial. We hope you found this of some help and also hope to see you soon with a new tutorial on ESP32.
Hello readers, I hope you all are doing great. In this tutorial, we will learn how to update a webpage using Server-Sent Events and the ESP32 web server.
| Where To Buy? | ||||
|---|---|---|---|---|
| No. | Components | Distributor | Link To Buy | |
| 1 | ESP32 | Amazon | Buy Now | |
It is a server push technology that enables the client devices to receive automatic updates from a server over HTTP (Hypertext Transfer Protocol) connection. SSE also describes how the server can initiate data transmission towards the client once an initial connection with the client has been established.
We have already posted a tutorial on how to implement Web socket protocol with ESP32 which is also a protocol used to notify events to a web client. Both the Server-Sent Events (SSE) and Web-Socket technologies seem to be quite similar but they are not.
The major difference between the two is that SSE is unidirectional, where the web client can only receive the updates from the ESP32 but it can’t send updates back to ESP32. On the other hand, the Web-socket protocol is bi-directional where both the web client and ESP32 can send and receive updates/events.
Fig. 1 Server-Sent event
The Server-Sent Event process initiates with an HTTP request from the web client or web page to the ESP32 web server. After that, the ESP32 is ready to send updates or events to the web client as they happen. But the web client can’t send any response or data to the ESP32 server after the initial handshake takes place.
Server-sent event technology can be used to communicate an event, GPIO states or to send sensor readings to the web client, whenever a new reading is observed.
For demonstration purpose, we are using a DHT11 sensor with the ESP32 module. ESP32 web server will display two things i.e., temperature and humidity observed using the DHT11 sensor. So, whenever a new reading is being observed, the ESP32 sends the reading to the Web Client over Server-sent events. After receiving the latest sensor reading the client updates the web page data.
Fig. 2 DHT11 sensor
DHT11 is a humidity and temperature sensor that measures its surrounding environment. It measures the temperature and humidity in a given area. It is made up of an NTC (negative temperature co-efficient) temperature sensor and a resistive humidity sensor. It also has an 8-bit microcontroller. The microcontroller is in charge of ADC (analog to digital conversion) and provides a digital output over the single wire protocol.
The DHT11 sensor can measure humidity from 20% to 90% with +-5 percent accuracy (RH or relative humidity) and temperature from 0 degrees Celsius to 50 degrees Celsius with +-2C accuracy.
DHT11 sensors can also be used to build a wired sensor network with a cable length of up to 20 meters.
Table 1
Note: Connect a 10K resistor between data and power (+5V) pin of DHT11 sensor module.
Fig. 3 ESP32 and DHT11 connections/wiring
We are using Arduino IDE to compile and upload code into the ESP32 module. You must have ESP32 board manager installed on your Arduino IDE to program the ESP32 module. To know more about Arduino IDE and how to use it, follow our previous tutorial i.e., on ESP32 programming series. The link is given below:
https://www.theengineeringprojects.com/2021/11/introduction-to-esp32-programming-series.html
Fig. 4 manage libraries
Fig. 5 Install DHT sensor library
ESP32 board manager doesn’t come with inbuilt libraries to create an asynchronous web server. So we need to download the library file from external sources and then add into Arduino IDE.
We need to install two library files:
Once you have successfully downloaded the required libraries, next step it to install or add these libraries in Arduino IDE.
To add the libraries in Arduino IDE, go to Sketch >> Include Library >> Add .zip library and then select the downloaded library files.
Fig. 6 adding necessary libraries
#include <WiFi.h>
#include <AsyncTCP.h>
#include <ESPAsyncWebServer.h>
#include "DHT.h"
#define DHTPIN 4 // Digital pin connected to the DHT sensor
#define DHTTYPE DHT11 // DHT 11
// Initializing the DHT11 sensor.
DHT dht(DHTPIN, DHTTYPE);
// Replace with your network credentials
const char* ssid = "SSID";
const char* password = "password";
// Create AsyncWebServer object on port 80
AsyncWebServer server(80);
// Create an Event Source on /events
AsyncEventSource events("/events");
// Timer variables
unsigned long lastTime = 0;
unsigned long timerDelay = 20000; //20 sec timer delay
//==== Creating web page
const char index_html[] PROGMEM = R"rawliteral(
<!DOCTYPE HTML><html>
<head>
<title>SSE with ESP32 Web Server</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.7.2/css/all.css" integrity="sha384-fnmOCqbTlWIlj8LyTjo7mOUStjsKC4pOpQbqyi7RrhN7udi9RwhKkMHpvLbHG9Sr" crossorigin="anonymous">
<link rel="icon" href="data:,">
<style>
html {font-family: Times New Roman; display: inline-block; text-align: justify;}
p { font-size: 1.2rem;}
body { margin: 0;}
.topnav { overflow: hidden; background-color: blue; color: white; font-size: 1rem; }
.content { padding: 20px; }
.card { background-color: #ADD8E6; box-shadow: 2px 2px 12px 1px rgba(140,140,140,.5); }
.cards { max-width: 600px; margin: 0 auto; display: grid; grid-gap: 2rem; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); }
.reading { font-size: 1.4rem; }
</style>
</head>
<body>
<div class="topnav">
<h1>Server-Sent Events </h1>
<h2> DHT11 Sensor Data </h2>
</div>
<div class="content">
<div class="cards">
<div class="card">
<p> DHT11 Temperature</p><p><span class="reading"><span id="temp">%TEMPERATURE%</span> °C</span></p>
</div>
<div class="card">
<p> DHT11 Humidity</p><p><span class="reading"><span id="hum">%HUMIDITY%</span> %</span></p>
</div>
</div>
</div>
<script>
if (!!window.EventSource)
{
var source = new EventSource('/events');
source.addEventListener('open', function(e)
{
console.log("Events Connected");
}, false);
source.addEventListener('error', function(e)
{
if (e.target.readyState != EventSource.OPEN)
{
console.log("Events Disconnected");
}
}, false);
source.addEventListener('message', function(e)
{
console.log("message", e.data);
}, false);
source.addEventListener('temperature', function(e)
{
console.log("temperature", e.data);
document.getElementById("temp").innerHTML = e.data;
}, false);
source.addEventListener('humidity', function(e)
{
console.log("humidity", e.data);
document.getElementById("hum").innerHTML = e.data;
}, false);
}
</script>
</body>
</html>)rawliteral";
void setup() {
Serial.begin(115200); //initialize serial monitor
//===set and initialize Wi-Fi
WiFi.mode(WIFI_STA);
WiFi.begin(ssid, password);
Serial.print("Connecting to WiFi ..");
while (WiFi.status() != WL_CONNECTED)
{
Serial.print('.');
delay(1000);
}
Serial.print("IP Address: ");
Serial.println(WiFi.localIP()); // print the IP address
//====Initialize DHT11 sensor
dht.begin();
//====Handle Web Server
server.on("/", HTTP_GET, [](AsyncWebServerRequest *request){
request->send_P(200, "text/html", index_html);
});
// Handle Web Server Events
events.onConnect([](AsyncEventSourceClient *client)
{
if(client->lastId())
{
Serial.printf("Client reconnected! Last message ID that it got is: %u\n",
client->lastId());
}
// send event with message "hello!", id current millis
// and set reconnect delay to 1 second
client->send("hello!", NULL, millis(), 10000);
});
server.addHandler(&events);
server.begin();
}
void loop()
{
delay(2000);
float humidity = dht.readHumidity();
// Read temperature as Celsius (the default)
float temperature = dht.readTemperature();
// Check if any reads failed and exit early (to try again).
if (isnan(humidity) || isnan(temperature))
{
Serial.println(F("Failed to read from DHT sensor!"));
return;
}
if ((millis() - lastTime) > timerDelay)
{
// Send Events to the Web Server with the Sensor Readings
events.send("ping",NULL,millis());
events.send(String(temperature).c_str(),"temperature",millis());
events.send(String(humidity).c_str(),"humidity",millis());
Serial.print(F("Humidity(%): "));
Serial.println(humidity);
Serial.print(F("Temp.: "));
Serial.print(temperature);
Serial.println(F("°C "));
}
}
Fig. 7 Header files
Fig. 8 Global declarations
Fig. 9
Fig. 10 Enter Network credentials
Fig. 11 Server port
Fig. 12 Event source
Fig. 13 Timer Variables
Fig. 14
Fig. 15
Fig. 16
Fig. 17
Fig. 18
Fig. 19
Fig. 20
Fig. 21 Fetch/obtain the IP address
Fig. 22 Initialize DHT sensor
Fig. 23
Fig. 24 Handling server events
Fig. 24 initializing web server
Fig. 25
Fig. 26 If error occurs while reading data from DHT11
Fig. 27 Sending events to the server
Fig. 28 Print Sensor data on the Serial monitor
Fig. 29 Select development board and COM port
Fig. 30
Fig. 31
This concludes the tutorial. I hope you found this of some help and also hope to see you soon with a new tutorial on ESP32.
Here, in this project, we are going to make an Up-Down counter. A simple counter counts in increasing or decreasing order but the Up-Down counter counts in increasing and decreasing order, both depending upon the input it has given.
But I am having an interesting question about the counter. Let suppose if the counter is counting in increasing order then up to which value, it will count because it can not count to infinite which means it has to reset after some certain value, and I believe that you must be having the same doubt as well. Basically every counter resets itself after a certain value and that value depends upon the bits of a counter.
Let suppose, we have a 8 bit counter which means it will count a maximum of up to 255 after which, it will reset to 0. So the size of the counter depends upon the bits of the counter.
So, in this project, we are going to make a counter which will count from 0 to 9 after which it will again reset to 0.
We will make this project in the simulation first, for that we will use a simulation software which is Proteus.
Proteus is a simulation software for electronics based circuits. In this software we can make different types of electronic circuits and we can run the simulation and can monitor the working of that project in real-time only.
And it is a good practice also while making any new project. First of all, we should make a simulation of that project so that we can debug any issues without damaging any real components.
Proteus has a very huge database of all types of electronics components pre-installed.
In this project, we will use the following components:
Truth Table for Modes
In this project, we will use two push buttons for controlling the counter as an Up counter or Down counter. The outputs from the push buttons will work as input for the BCD/DECADE UP/DOWN COUNTER IC. When we press the push button, there will be a change in the signal pin of the IC and according to the truth table when the signal changes from logic HIGH to LOW and the other input clock pin is at HIGH state then it will change the output count value depending upon the selected pin.
Which means if we push the Up counter push button, it will send a pulse to CpU pin of the IC, afterwards it will process as the increment in the output value, so it will increase the current output value by one. Similarly, for the Down counter push button, when we press the button, it will send a pulse to the CpD pin of the IC, thereafter it will process as the decrement in the output value so it will decrease the current output value by one.
And the outputs of the BCD/DECADE UP/DOWN COUNTER IC will work as the input for the BCD to 7-Segment Decoder. And the output pins of the BCD to 7-Segment Decoder will be connected to the 7 segment LED with some protection resistor to prevent them from damaging.
The 7-Segment Led display will glow the LEDs depending upon the output values on the BCD to 7-Segment Decoder/Driver.
Now we know the workflow of our counter.
So let‘s move to the circuit of the counter.
For making the project, we will be using the Proteus simulation software.
Now we have our circuit ready, it is time to test it.
I hope we have covered all the aspects of this project. And I think it will be a very useful learning project as well. Now if we see any scoreboard, immediately we will be knowing the electronics behind it. I hope you have enjoyed reading this project. Please let us know in the comment section if you have faced any issues while making this project.
Thanks for reading this article. See you in the next project.
ESP32 module comes with multiple inbuilt features and peripheral interfacing capability is one of those features. ESP32 module also consists of an inbuilt temperature sensor, but that can only measure the temperature of the ESP32 core not the temperature of the surrounding environment. So it is required to use a peripheral sensor to measure the temperature of the surrounding environment like home, garden, office etc.
Hello readers. I hope you all are doing great. In this tutorial, we will learn how to interface DHT11 (temperature and humidity sensor) with the ESP32. Later in this tutorial, we will discuss how to share the sensor readings obtained from the DHT11 sensor to a web server.
Before moving towards the interfacing and programming part, let’s have a short introduction to the DHT11 sensor, its working and its connections.
| Where To Buy? | ||||
|---|---|---|---|---|
| No. | Components | Distributor | Link To Buy | |
| 1 | ESP32 | Amazon | Buy Now | |
Fig. 1: DHT11 sensor
DHT11 is used to measure humidity and temperature from its surrounding. It monitors the ambient temperature and humidity of a given area. It consists of an NTC (negative temperature co-efficient) temperature sensor and a resistive type humidity sensor. It also consists of an 8-bit microcontroller. The microcontroller is responsible for performing ADC (analog to digital conversion) and provides a digital output over the single wire protocol.
DHT11 sensor can measure humidity from 20% to 90% with +-5% (RH or relative humidity) of accuracy and can measure the temperature in the range of 0 degrees Celsius to 50 degrees Celsius with +-2C of accuracy.
DHT11 sensors can also be used to implement a wired sensor system using a cable length of up to 20 meters.
There are two DHT modules (DHT11 and DHT22) available in the market to measure temperature and humidity. The purpose of both module are same but with different specifications. Like DHT22 sensor provides broader temperature and humidity sensitivity ranges. But DHT22 is costlier than DHT11. So you can prefer to use any of the module, as per your requirements.
Table: 1
Note: Connect a 10K resistor between data and power (+5V) pin of DHT11 sensor module.
Fig. 2: ESP32 and DHT11 connections/wiring
We are using Arduino IDE to compile and upload code into ESP32 module. To know more about Arduino IDE and how to use it, follow our previous tutorial i.e., on ESP32 programming series. Link is given below:
https://www.theengineeringprojects.com/2021/11/introduction-to-esp32-programming-series.html
DHT11 sensor uses single wire protocol to communicate data which requires a precise timing. In order to interface DHT11 sensor with ESP32 module it is required to add necessary libraries. To install the DHT11 sensor library;
Fig. 3: manage libraries
Fig. 4: Install DHT sensor library
#include "DHT.h"
#define DHTPIN 4 // Digital pin connected to the DHT sensor
#define DHTTYPE DHT11 // DHT 11
// Initializing the DHT11 sensor.
DHT dht(DHTPIN, DHTTYPE);
void setup() {
Serial.begin(115200);
Serial.println(F("DHT test string!"));
dht.begin();
}
void loop() {
// Wait a few seconds between measurements.
delay(2000);
// Reading temperature or humidity takes about 250 milliseconds!
// Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
float h = dht.readHumidity();
// Read temperature as Celsius (the default)
float t = dht.readTemperature();
// Read temperature as Fahrenheit (isFahrenheit = true)
float f = dht.readTemperature(true);
// Check if any reads failed and exit early (to try again).
if (isnan(h) || isnan(t) || isnan(f)) {
Serial.println(F("Failed to read from DHT sensor!"));
return;
}
// Compute heat index in Fahrenheit (the default)
float hif = dht.computeHeatIndex(f, h);
// Compute heat index in Celsius (isFahreheit = false)
float hic = dht.computeHeatIndex(t, h, false);
Serial.print(F("Humidity(%): "));
Serial.println(h);
Serial.print(F("Temp.: "));
Serial.print(t);
Serial.println(F("°C "));
Serial.print(F("Temp.: "));
Serial.print(f);
Serial.println(F("°F "));
Serial.print(F("Heat index: "));
Serial.println(hic);
Serial.println(" ");
Serial.print(F("°C "));
Serial.print(hif);
Serial.println(F("°F"));
}
Fig. 5: Add necessary libraries
Fig. 6: Global declarations
Fig. 7
Fig. 9
Fig. 10
Fig. 11
Fig. 12: Heat index
Fig. ESP32 and DHT11 interfacing
Fig. 13: Readings observed from DHT11 sensor
The IoT is the interconnection of physical objects or devices with sensors and software accessing capabilities to communicate data or information over the internet.
To build an IoT network, we need an interface medium that can fetch, control, and communicate data between sender and receiver electronics devices or servers.
Espressif Systems created the ESP32 Wi-Fi chip series. The ESP32 module is equipped with a 32-bit Tensilica microcontroller, 2.4GHz Wi-Fi connectivity, an antenna, memory, and power management modules, and much more. All of these built-in features of this ESP32 module make it ideal for IoT applications.
It is an open data platform for the Internet of Things (Internet of Things). ThingSpeak is a MathWorks web service that allows us to send sensor readings/data to the cloud. We can also visualise and act on the data (calculate the data) sent to ThingSpeak by the devices. Data can be stored in both private and public channels.
ThingSpeak is commonly used for internet of things prototyping and proof of concept systems requiring analytics.
Fig. 14: Getting started for free
Fig. 15: Create new account
Fig. 16: MathWorks Sign in
Fig. 17: New Channel
Fig. 18: Fill the channel details
Fig. 19: Field Chart Edit
https://github.com/mathworks/thingspeak-arduino
Fig. 20: Adding ThingSpeak library
To check whether the library is successfully added or not:
Fig. 21: manage libraries
Fig. 22: Arduino IDE Library manager.
//------style guard ----
#ifdef __cplusplus
extern "C" {
#endif
uint8_t temprature_sens_read();
#ifdef __cplusplus
}
#endif
uint8_t temprature_sens_read();
// ------header files----
#include <WiFi.h>
#include "DHT.h"
#include "ThingSpeak.h"
//-----netwrok credentials
char* ssid = "replace this with your SSID"; //enter SSID
char* passphrase = "replace this with your password"; // enter the password
WiFiServer server(80);
WiFiClient client;
//-----ThingSpeak channel details
unsigned long myChannelNumber = 3;
const char * myWriteAPIKey = "replace this with your API key";
//----- Timer variables
unsigned long lastTime = 0;
unsigned long timerDelay = 1000;
//----DHT declarations
#define DHTPIN 4 // Digital pin connected to the DHT sensor
#define DHTTYPE DHT11 // DHT 11
// Initializing the DHT11 sensor.
DHT dht(DHTPIN, DHTTYPE);
void setup()
{
Serial.begin(115200); //Initialize serial
Serial.print("Connecting to ");
Serial.println(ssid);
WiFi.begin(ssid, passphrase);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
// Print local IP address and start web server
Serial.println("");
Serial.println("WiFi connected.");
Serial.println("IP address: ");
Serial.println(WiFi.localIP());
server.begin();
//----nitialize dht11
dht.begin();
ThingSpeak.begin(client); // Initialize ThingSpeak
}
void loop()
{
if ((millis() - lastTime) > timerDelay)
{
delay(2500);
// Reading temperature or humidity takes about 250 milliseconds!
float h = dht.readHumidity();
// Read temperature as Celsius (the default)
float t = dht.readTemperature();
float f = dht.readTemperature(true);
if (isnan(h) || isnan(t) || isnan(f)) {
Serial.println(F("Failed to read from DHT sensor!"));
return;
}
Serial.print("Temperature (ºC): ");
Serial.print(t);
Serial.println("ºC");
Serial.print("Humidity");
Serial.println(h);
ThingSpeak.setField(1, h);
ThingSpeak.setField(2, t);
// Write to ThingSpeak. There are up to 8 fields in a channel, allowing you to store up to 8 different
// pieces of information in a channel. Here, we write to field 1.
int x = ThingSpeak.writeFields(myChannelNumber,
myWriteAPIKey);
if(x == 200){
Serial.println("Channel update successful.");
}
else{
Serial.println("Problem updating channel. HTTP error code " + String(x));
}
lastTime = millis();
}
}
Fig. 23: Libraries
Fig. 24
Fig. 25: server port
Fig. 26
Fig. 29
Fig. 30: connect to wifi
Fig.31: Fetch and print IP address
Fig. 32
Fig. 33
Fig. 34
Fig. 35
Fig. 36: Displaying humidity on thingSpeak server
Fig. 37: Displaying Temperature on ThingSpeak server
This concludes the tutorial. I hope you found this of some help and also hope to see you soon with new tutorial on ESP32.
