HMI Touch Display: Nextion and TJC Screens for Arduino Projects

HMI touch displays like Nextion and TJC screens bring professional-grade touch interfaces to Arduino projects without consuming valuable microcontroller resources. Unlike traditional TFT displays that rely on the Arduino for all graphics rendering, Nextion displays have their own onboard processor and memory, handling all visual elements independently. The Arduino communicates via simple serial commands, making it possible to create complex industrial dashboards, home automation panels, and machine control interfaces with minimal code.

Table of Contents

• What is an HMI Display
• Nextion vs TJC Comparison
• Nextion Editor Software
• Serial Communication Protocol
• Industrial Dashboard Project
• Home Automation Panel
• Frequently Asked Questions
• Conclusion

What is an HMI Display

HMI (Human Machine Interface) displays are self-contained units with their own processor, flash memory, and touch controller. They run a GUI designed in PC-based editor software and communicate with external microcontrollers via serial (UART). This architecture means the Arduino only sends data values (sensor readings, states) and receives touch events, while the display handles all rendering.

Nextion vs TJC Comparison

TJC displays are essentially the same hardware as Nextion at a lower price. However, Nextion has better English documentation, larger community, and more Arduino libraries. For Indian buyers, Nextion is recommended for better support.

Nextion Editor Software

The Nextion Editor (free download) is a drag-and-drop GUI builder. Design pages with buttons, text fields, gauges, sliders, progress bars, and images. Key features:

• Pages: Multiple screens navigated by touch
• Components: Text, number, button, slider, gauge, progress bar, picture, crop, timer, checkbox, radio
• Events: Touch press, touch release, timer, and custom serial events
• Fonts: Custom fonts with Indian language support (generate .zi font files)

Design the GUI in the editor, compile, and upload to the Nextion display via SD card or USB-TTL adapter. The design is stored in the display’s flash memory and runs independently.

Serial Communication Protocol

Nextion uses a simple serial protocol. Commands are ASCII strings terminated by three 0xFF bytes.

#include <SoftwareSerial.h>

SoftwareSerial nexSerial(10, 11); // RX, TX

void setup() {
  Serial.begin(9600);
  nexSerial.begin(9600);
}

// Send value to a text component
void setText(String component, String value) {
  nexSerial.print(component + ".txt="" + value + """);
  nexSerial.write(0xFF);
  nexSerial.write(0xFF);
  nexSerial.write(0xFF);
}

// Send value to a number component
void setNumber(String component, int value) {
  nexSerial.print(component + ".val=" + String(value));
  nexSerial.write(0xFF);
  nexSerial.write(0xFF);
  nexSerial.write(0xFF);
}

void loop() {
  float temp = 28.5; // From sensor
  setText("t0", String(temp, 1) + " C");
  setNumber("j0", (int)(temp * 10)); // Progress bar
  delay(1000);
}

Industrial Dashboard Project

Build a 7″ Nextion display dashboard for monitoring industrial equipment. Display motor RPM (gauge component), bearing temperature (number + progress bar), vibration level (waveform component), and operating hours (text). Touch buttons for motor start/stop, speed adjustment, and alarm acknowledgement. The Arduino Mega reads sensors and serial-communicates with the Nextion while also controlling relays.

Home Automation Panel

A 5″ Nextion touch panel makes an excellent wall-mounted home automation controller for Indian homes. Create pages for:

• Living room: Fan speed (5 levels), lights on/off, AC temperature setpoint
• Kitchen: Geyser on/off with timer, exhaust fan control
• Security: Gate camera view (on Intelligent series), lock/unlock
• Energy: Current power consumption, daily units used, monthly bill estimate

Frequently Asked Questions

Can Nextion displays show camera video?

Only the Intelligent series (NI series) supports video playback from onboard flash. Basic and Enhanced series cannot display video. For real-time camera feed, use a separate monitor or a Raspberry Pi with a touchscreen.

How do I update the Nextion firmware in the field?

Copy the compiled .tft file to a FAT32-formatted microSD card, insert into the Nextion’s SD slot, and power cycle. The display automatically updates from the SD card. This allows field updates without connecting to a computer.

What is the maximum cable length for serial communication?

TTL serial (3.3V/5V) works reliably up to 1-2 metres. For longer distances, convert to RS485 using a MAX485 module at each end. RS485 supports up to 1200 metres, making it suitable for factory floor installations.

Can I use Hindi or regional language text on Nextion?

Yes. Generate a custom font file (.zi) in the Nextion Editor using a Unicode font that includes Devanagari or other Indian scripts. The generated font file is uploaded with the project and supports full Hindi, Marathi, Gujarati, and other language text display.

Conclusion

Nextion and TJC HMI touch displays bring professional-grade interfaces to Arduino projects with minimal programming effort. The drag-and-drop editor, serial communication simplicity, and self-contained rendering make them ideal for industrial dashboards, home automation panels, and any project requiring a polished touchscreen interface. Find Nextion displays and compatible microcontrollers at Zbotic to elevate your project’s user interface.