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LCD 20x4 (Parallel)

A spacious 20-column by 4-row alphanumeric display utilizing the classic Hitachi HD44780 parallel interface.

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20x4 LCD

A classic alphanumeric liquid crystal display based on the HD44780 controller. It can display 20 characters per line across 4 lines. This version uses a parallel interface requiring at least 6 digital pins.

DisplaysParallelText

Overview

Because this module doesn't use an I2C backpack, you must wire 6 digital lines (in 4-bit mode) directly to the Arduino, plus power and contrast lines. It offers more screen real estate (80 chars total) than the 16x2 version but uses the same underlying HD44780 controller commands.

Pin Reference

Pin	Type	Description
VSS	power	Ground (GND).
VDD	power	Power (5V).
V0	analog	Contrast Adjustment. Usually connected to a potentiometer.
RS	digital	Register Select (0 = Instruction, 1 = Data).
RW	digital	Read/Write. Tie to GND for Write-only.
E	digital	Enable signal.
D0-D3	digital	Lower data pins (not used in standard 4-bit mode).
D4-D7	digital	Higher data pins (used for both 4-bit and 8-bit modes).
A	power	Backlight Anode (+5V).
K	power	Backlight Cathode (GND).

Configurable Attributes

Attribute	Type	Default	Description
color	string	blue	The backlight color in the simulator (e.g., blue or green).

Wiring Diagram (4-bit Mode)

Example Arduino Code

This uses the standard Arduino LiquidCrystal library built into the IDE. Notice the lcd.begin(20, 4) initialization.

#include <LiquidCrystal.h>

// Initialize the library with the numbers of the interface pins
// LiquidCrystal(rs, enable, d4, d5, d6, d7)
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup() {
  // Set up the LCD's number of columns and rows (20x4):
  lcd.begin(20, 4);
  
  lcd.setCursor(0, 0);
  lcd.print("OpenHW Studio!");
  
  lcd.setCursor(0, 1);
  lcd.print("20x4 LCD Display");
}

void loop() {
  lcd.setCursor(0, 2);
  lcd.print("Timer: ");
  lcd.print(millis() / 1000);
  
  lcd.setCursor(0, 3);
  lcd.print("Running smoothly...");
}

Simulation Notes

• The simulator automatically assumes max contrast if V0 is wired directly to ground.
• You can leave D0-D3 completely disconnected in the simulator when using 4-bit mode.

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