7 segment display interfaced with nodemcu WiFi module: Displaying numbers on seven segment display through a web page

This tutorial is on interfacing 7 segment display with nodemcu esp8266 12e WiFi module. Numbers are going to be displayed on 7 segment display. Seven segment display control is given to a web page. Web page contain buttons. Their are total 9 buttons and each button is assigned a number from 1 to 9. Pressing any button will display its corresponding number on the 7 segment display. Nodemcu is working as a server. It is serving a web page. To access a server we need a client. For our project client can be any device which can connect to a WiFi network and has a browser in it. Desktop computer. laptop, mobile or a note book can be a client in our case. We have to enter the web server(nodemcu) address in our browser to access the web page(7 segment control page). Before moving forward to circuit diagram and code of the project i suggest you to take a simple tutorial on types of seven segment display and their pin out etc. Click the below button to take the tutorial.

Difference between common anode and cathode 7 segment dispaly

Project circuit diagram

I am going to use common anode 7 segment display in this project. After taking the above tutorial i hope you know about the common anode 7 segment display pin out and its working requirements. Nodemcu and common anode pin connections are below.

Nodemcu GPIO#0 is connected with Pin ‘a’ of 7 segment display.
Nodemcu GPIO#1 is connected with Pin ‘b’ of 7 segment display.
Nodemcu GPIO#2 is connected with Pin ‘c’ of 7 segment display.
Nodemcu GPIO#3 is connected with Pin ‘d’ of 7 segment display.
Nodemcu GPIO#4 is connected with Pin ‘e’ of 7 segment display.
Nodemcu GPIO#5 is connected with Pin ‘f’ of 7 segment display.
Nodemcu GPIO#16 is connected with Pin ‘g’ of 7 segment display.

7 segment display can work on 3.3 volts to +5 volts. Nodemcu WiFi module also works on 3.3 volts and outputs 3.3 volts at its power out pins. I used 3.3 volts out of nodemcu to power the common anode 7 segment display. Com/vcc pin of 7 segment display is connected 3.3 volt pin of nodemcu. Its better to connect a 110 ohm resistor in series to com/vcc pin of 7 segment display with 3.3 volt pin of nodemcu to limit the current. I did not used the register but i suggest to use it if your input supply to nodemcu esp8266 is low current output power source. Resistor will limit the current and prevents the nodemcu from low power reset. Circuit diagram of the project is given below.

7-Segment display with nodemcu over WiFi using arduino ide

Coming to the code portion of the project. First i included the header file ESP8266WiFi.h. I am going to use many nodemcu HTTP functions defined in this library. After header file SSID and Password of WiFi network is required. One must enter the SSID and Password of the network to which he wants nodemcu to be connected to.

const char* ssid = “Your SSID”;
const char* password = “Your Wifi Password”;

Enter the SSID and password in the double quotations. After network configurations nodemcu pins are defined. These nodemcu esp8266 pins are going to be interfaced to 7 segment display. In the setup function first the serial channel of nodemcu is defined and communication baud rate is set to 115200 bps. Then nodemcu 7 segment display interconnecting pins are initialized as output. On wards nodemcu requests your router/WiFi network(The one whose SSID and Password are entered above) for an IP allotment. After IP allotment its time for nodemcu server start up. I will discus about the server later in the tutorial.
In the loop function nodemcu(server) is checking for a client request as soon as the client request arrives nodemcu starts decoding the request. Performs the functions requested in the HTTP request by client. Before closing the client HTTP request server-nodemcu replies back to client with the updated status of 7 segment display.

Just build the circuit and download the above code in your nodemcu esp8266 WiFi module. After successfully downloading the code in your nodemcu. Open the arduino serial monitor from the arduino ide. You will see in arduino serial monitor nodemcu starting up, requesting IP from router and after IP assignment starting its server. Server address will be printed in the arduino serial monitor. This server address is actually the web page address on which our 7 segment display controls are present. One must has to enter this URL/Address in his browser to access the seven segment control web page.

Note: Both the server(nodemcu esp8266 12 e) and client(mobile, desktop, laptop) must be connected to same network in order to work properly. If they are on different networks your client will be unable to access the 7 segment control web page.
As soon as you hit the 7 segment display web page control address/IP in your browser a web page will appear in browser. Web page will look like some thing below. Main project heading is on the top. Then the current displayed number on seven segment status is shown. Below status are control buttons. Pressing any button will automatically display the corresponding number on 7 segment.

7 segment display with nodemcu web page WiFi controls

So what happens when you press the button? When a button is pressed a client request arrives to the server. Server checks the request and responds to it. For example if you pressed ‘Display-1’ button on 7 segment control page. At server side the statement

if (request.indexOf(“/Req=1”) != -1)

becomes true. Now what ever is in this statement, nodemcu esp8266 will execute it. In this statement I am printing 1 on seven segment display. To print we know we have to make the seven segment pins off and on. So for 1 we have to switch on ‘e’ and ‘f’ pins of seven segment and all other will be off. The code below is executed in the above statement and in it ‘e’ and ‘f’ are switched on.
digitalWrite(a, HIGH);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, HIGH); //Displaying 1
digitalWrite(e, LOW);
digitalWrite(f, LOW);
digitalWrite(g, HIGH);
Note: We are using common anode 7 segment display. So to glow an led corresponding to seven segment pin we have to make it low. This is done in the above statements.

Future Work
This tutorial is just to teach you how to interface and control a 7 segment display over WiFi through nodemcu WiFi module. Further you can set time of a digital watch with the same protocol. Display characters on lcd. Make a diy web key pad etc.

Download the project code. Folder contains the arduino project .ino file. Code is open source one can use and modify it according to his needs. Please provide us with your feed back on the project.

Code/Files