Build Instructions

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• 1

  Understanding the Hardware

  Now that we've covered the project overview, let's assemble the hardware.

  One of the best things about this project is that it requires only two main devices:

  • ESP32-S3-BOX-3
  • QR204 Thermal Printer

  Unlike many printer projects that require shields or complicated driver boards, the QR204 communicates directly using UART, making it extremely beginner-friendly.

  Before making any connections, let's briefly understand the purpose of each component.

  ESP32-S3-BOX-3

  The ESP32-S3-BOX-3 serves as the brain of the project.

  It is responsible for:

  • Running the Arduino program.
  • Detecting touch events on the display.
  • Sending UART data to the printer.
  • Displaying the printer status.
  • Managing the user interface.

  Since the board already includes a high-quality touchscreen display, we don't need external push buttons or LCD modules.

  This allows us to create a clean Human Machine Interface (HMI) using only the built-in display.

  Image Placeholder:ESP32-S3-BOX-3 Development Board

  QR204 Thermal Printer

  The QR204 is a compact thermal printer capable of printing plain text, receipts, QR codes, barcodes, and graphics.

  Instead of using ink cartridges, it prints by heating specially coated thermal paper.

  Some advantages include:

  • No ink required
  • High-speed printing
  • Low maintenance
  • Quiet operation
  • Compact size
  • UART interface
  • ESC/POS command support

  Since the printer communicates using UART, interfacing it with an ESP32 is remarkably simple.

  Understanding UART Communication

  One of the most important concepts in this project is UART communication.

  UART stands for Universal Asynchronous Receiver Transmitter.

  It is a serial communication protocol that allows two electronic devices to exchange data one byte at a time.

  Unlike SPI or I²C, UART requires only two communication lines:

  • TX (Transmit)
  • RX (Receive)

  Think of UART as a one-way conversation.

  The ESP32 "speaks" by transmitting data through its TX pin.

  The printer "listens" by receiving data through its RX pin.

  Whenever the ESP32 sends a character, the printer immediately prints it.

  For example:

  PrinterSerial.println("Hello World!");

  Each character is transmitted individually:

  HelloWorld!

  The printer receives these characters and prints them exactly as they arrive.

  This simplicity makes UART one of the easiest communication methods for beginners.

  Understanding the Wiring

  The QR204 printer requires only a few connections.

  QR204 Printer

  ESP32-S3-BOX-3

  RX

  GPIO43 (TX)

  TX

  GPIO44 (RX) (Optional)

  GND

  GND

  VCC

  External 5V Supply

  Image Placeholder:Complete Wiring Diagram

  Notice something interesting.

  The printer's RX pin connects to the ESP32's TX pin.

  This often confuses beginners.

  The reason is simple.

  The ESP32 is transmitting data.

  The printer is receiving data.

  Therefore:

  ESP32 TX        │        ▼Printer RX

  Similarly,

  ESP32 RX        ▲        │Printer TX

  Although the printer's TX pin isn't required for this simple project, connecting it allows future two-way communication if needed.

  Powering the Thermal Printer

  One of the most common mistakes beginners make is trying to power the thermal printer directly from the ESP32.

  Thermal printers draw a relatively high current, especially while heating the print head.

  Because of this, it is strongly recommended to power the QR204 using a stable external 5V power supply capable of supplying sufficient current.

  The ESP32-S3-BOX-3 should continue to be powered through its USB Type-C connection.

  Keeping the printer and ESP32 power supplies stable helps prevent unexpected resets during printing.

  Tip: If your printer behaves erratically or the ESP32 restarts while printing, inadequate power is often the first thing to check.

• 2

  Preparing the Arduino IDE

  With the hardware assembled, the next step is preparing the Arduino development environment.

  If you've already worked with ESP32 boards before, most of these steps will feel familiar.

  If this is your first ESP32 project, don't worry—we'll go through everything step by step.

  Install the ESP32 Board Package

  Open the Arduino IDE.

  Navigate to:

  File → Preferences

  Locate the field labelled:

  Additional Boards Manager URLs

  If it's empty, paste the following URL:

  https://espressif.github.io/arduino-esp32/package_esp32_index.json

  Click OK.

  Next, open:

  Tools → Board → Boards Manager

  Search for:

  ESP32

  Install the latest board package published by Espressif Systems.

  Image Placeholder:Installing ESP32 Board Package

  Select the Correct Board

  Connect the ESP32-S3-BOX-3 to your computer using a USB Type-C cable.

  Now navigate to:

  Tools → Board

  Select:

  ESP32S3 Dev Module

  or

  ESP32-S3-BOX-3

  depending on the board definitions available in your installed package.

  Next, select the correct COM port from:

  Tools → Port

  Installing the Required Libraries

  This project uses only a few libraries.

  Open:

  Sketch → Include Library → Manage Libraries

  Install:

  • LovyanGFX
  • LGFX_AUTODETECT

  The following libraries are already included with the ESP32 board package:

  • HardwareSerial
  • Wire
  • SPI

  So no additional installation is required for those.

• 3

  Uploading the Program

  Open the Arduino sketch provided with this tutorial.

  Before uploading the code, verify the UART pin definitions:

  #define TXD2 43
  #define RXD2 44

  These correspond to the UART pins used to communicate with the QR204 printer.

  If your hardware uses different pins, simply update these values.

  Now click the Verify button.

  If no compilation errors appear, click Upload.

  The upload process typically takes less than a minute.

  Once complete, the ESP32 will automatically restart and display the main screen with the Print button.

  In the next section, we'll walk through the program itself, explain how the code communicates with the printer, and perform our very first thermal print.

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