Introduction

Theesp32 tutorialAims to explain how to use the Arduino coreESP32The development board is connected toSSD1306 OLEDDisplay and print the "Hello World" message. This tutorial uses the OLED version of Elecrow. The ESP32 board model used is NodeMCU.

In order to facilitate the interaction with the display, we need to install a library that supports the above display model and can be used on the ESP32 development board. You can view the library in Figure 1 below and install it through the Arduino IDE library manager.

You can view the library's GitHub page here, which details the APIs that can interact with the display.

Figure 1-Install the OLED library.

This tutorial uses the OLED version of Elecrow. It can also be used as a part of this startup kit, the ESP32 board used is NodeMCU.

Electrical diagram

ESP32 will interact with SSD1306 display through I2C. Therefore, in addition to the power supply, we only need two wires between the devices.

The electrical diagram is shown in Figure 2 below. We use ESP32 pins 21 and 22 as I2C SDA and SCL respectively.

Since the operating voltage of the SSD1306 is 3.3 V, we can use the 3.3 V power pin that most ESP32 boards have to power the display.

Please note that depending on your development board model, the pin marked name or number may not match the ESP32 microcontroller name or number. Before continuing the actual wiring, you should check the pin mapping relationship of the circuit board and confirm it.

Figure 2-Electrical diagram between ESP32 and SSD1306 OLED display.

Code

The code for this tutorial is very simple, because the library we just installed has a very easy-to-use API.

First, we need to include the Wire.h library, which is required for I2C communication with OLED displays. We also need to add the SSD1306.h library, we will use it to interact with the device.

#include <wire.h>

#include "SSD1306.h"

Next, we need to declare the SSD1306 class object, which will provide the functions needed for drawing in the display. We will call this object to display.

The class constructor receives the I2C address of the device as the first parameter, that is, 0x3c. For the second and third parameters, the constructor receives the number of SDA and SCL pins, respectively. In our example, we use pins 21 and 22 of ESP32 as shown in the schematic diagram.

SSD1306 display(0x3c, 21, 22);

Now, in the setup function, we will initialize the display by calling the init method of the display object. This method does not receive any parameters and returns void.

display.init();

Next we can start drawing on the display. For this simple example, we will draw a very simple "Hello World" message. To do this, we can call the drawString method of the display object.

This method receives x and y coordinates as the first and second parameters, where the string will be drawn on the display, and as the third parameter, it receives the string with actual content.

display.drawString(0, 0, "Hello World");

Finally, in order to send the content to the display for effective drawing, we need to call the display method on the object. This method does not receive any parameters.

display.display();

Since we are not going to change the display content, we may leave an empty Arduino loop function. Once the connection is successful, the string we just drew will remain on the display. The final source code is shown below.

#include <Wire.h>

#include "SSD1306.h"

 

SSD1306  display(0x3c, 21, 22);

 

void setup() {

 

  display.init();

  display.drawString(0, 0, "Hello World");

  display.display();

}

 

void loop() {}

Code test

If you need to test the code, after completing the wiring specified in the diagram in Figure 1, you only need to compile it and upload it to the ESP32 development board using the Arduino IDE.

After executing the program, a "Hello World" message will appear on the display, as shown in Figure 3.

Note: The author of this article is Nuno Santos, an amiable electronic and computer engineer who lives in Lisbon, Portugal.
He has written more than 200 useful tutorials and projects about ESP32 and ESP8266. It involves arduino, micropython, Picoweb, Espruino, Bluetooth, RFID, IDF, etc. It is very extensive, and it is not an exaggeration to say that it is the most comprehensive.

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