How to Use LCD 16x2 display with attached PCF8574 (I2C Module): Examples, Pinouts, and Specs

The LCD 16x2 display with an attached PCF8574 I2C module is a versatile and widely used electronic component for displaying alphanumeric characters. The display features two rows, each capable of showing 16 characters, making it ideal for presenting information such as sensor readings, system statuses, or user prompts. The inclusion of the PCF8574 I2C module simplifies communication with microcontrollers by reducing the required number of pins to just two (SDA and SCL), enabling easier wiring and more efficient use of GPIO pins.

• Embedded systems and microcontroller projects
• Home automation displays
• Sensor data visualization
• Menu-based user interfaces
• Educational and prototyping purposes

The PCF8574 I2C module reduces the number of pins required to control the LCD. Below is the pin configuration for the I2C module:

1. Wiring the LCD with a Microcontroller:

   • Connect the VCC pin of the I2C module to the 5V pin of the microcontroller.
   • Connect the GND pin of the I2C module to the ground (GND) of the microcontroller.
   • Connect the SDA pin of the I2C module to the SDA pin of the microcontroller (e.g., A4 on Arduino UNO).
   • Connect the SCL pin of the I2C module to the SCL pin of the microcontroller (e.g., A5 on Arduino UNO).

2. Install Required Libraries:

   • Use the Arduino IDE and install the LiquidCrystal_I2C library. This library simplifies the process of controlling the LCD via I2C.

3. Adjust the Contrast:

   • Use the potentiometer on the I2C module to adjust the contrast of the display.

4. Upload Code:

   • Use the example code below to test the display.

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// Initialize the LCD with I2C address 0x27 and dimensions 16x2
LiquidCrystal_I2C lcd(0x27, 16, 2);

void setup() {
  lcd.begin(); // Initialize the LCD
  lcd.backlight(); // Turn on the backlight
  lcd.setCursor(0, 0); // Set cursor to the first row, first column
  lcd.print("Hello, World!"); // Print a message on the first row
  lcd.setCursor(0, 1); // Set cursor to the second row, first column
  lcd.print("I2C LCD Test"); // Print a message on the second row
}

void loop() {
  // No actions in the loop for this example
}

• I2C Address: The default I2C address is typically 0x27, but it may vary depending on the module. Use an I2C scanner sketch to determine the correct address if needed.
• Power Supply: Ensure the module is powered with 5V. Supplying incorrect voltage may damage the component.
• Contrast Adjustment: If the text is not visible, adjust the contrast using the potentiometer on the I2C module.
• Backlight Control: The backlight can be turned on or off programmatically using the lcd.backlight() and lcd.noBacklight() functions.

1. No Text Displayed on the LCD:

   • Verify the wiring connections (SDA, SCL, VCC, GND).
   • Check the I2C address using an I2C scanner sketch.
   • Adjust the contrast using the potentiometer.

2. Garbage Characters or Incorrect Display:

   • Ensure the correct I2C address is specified in the code.
   • Verify that the LiquidCrystal_I2C library is installed and up to date.

3. Backlight Not Working:

   • Ensure the lcd.backlight() function is called in the code.
   • Check the power supply to the module.

4. I2C Communication Errors:

   • Confirm that the SDA and SCL pins are correctly connected.
   • Ensure no other devices on the I2C bus are causing address conflicts.

• Q: Can I use this module with a 3.3V microcontroller?
  A: The module is designed for 5V operation. Use a level shifter if connecting to a 3.3V microcontroller.

• Q: How do I find the I2C address of my module?
  A: Use an I2C scanner sketch to detect the address. This is especially useful if the default address (0x27) does not work.

• Q: Can I control the backlight brightness?
  A: The backlight is either on or off by default. For brightness control, you would need to modify the hardware or use a PWM signal.

• Q: What is the maximum cable length for I2C communication?
  A: The maximum length depends on the pull-up resistors and communication speed, but typically it is recommended to keep the length under 1 meter for reliable operation.

This documentation provides a comprehensive guide to using the LCD 16x2 display with an attached PCF8574 I2C module. By following the instructions and best practices, you can easily integrate this component into your projects.