Embedded Interface LCD HD44780

• HD44780 compliant controllers 16×2 Character LCD is a very basic and low-cost LCD module that is commonly used in electronic products and projects.
• 16×2 means it contains 2 rows that can display 16 characters.
• Its other variants such as 16×1 and 16×4 are also available in the market.

LCD4 Bit Mode Functions

• Lcd4_Clear() → Clears the screen
• Display functions (0x0B–0x0E) → Set display, cursor, and blink states
• Shift functions (0x18/0x1C) → Scroll the display left/right

Understanding HD44780 Commands

• 0x01 → Clear Display
• 0x0B → Display OFF, Blink ON, Cursor ON
• 0x0C → Display ON, Blink OFF, Cursor OFF
• 0x0D → Display ON, Blink OFF, Cursor ON
• 0x0E → Display ON, Blink ON, Cursor OFF
• 0x08, 0x0C, 0x18, 0x1C → Cursor or display shift commands

Commands are sent using a function like Lcd4_Cmd() in 4-bit mode, which splits each byte into two nibbles for transmission.

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Function Explanation

a) Clear Screen

void Lcd4_Clear() {
  Lcd4_Cmd(0x00);
  Lcd4_Cmd(0x01);
}

• 0x01 clears the display and sets the cursor at the home position.
• The first 0x00 is likely a control prefix for 4-bit mode.

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b) Display Modes

void Lcd4_DisplayOFF_BlinkON_CursorON() {
  Lcd4_Cmd(0x00);
  Lcd4_Cmd(0x0B);
}

• Turns display off, enables blinking cursor, and sets cursor visible.

void Lcd4_DisplayON_BlinkOFF_CursorOFF() {
  Lcd4_Cmd(0x00);
  Lcd4_Cmd(0x0C);
}

• Turns display on, disables blinking, hides the cursor.

void Lcd4_DisplayON_BlinkOFF_CursorON() {
  Lcd4_Cmd(0x00);
  Lcd4_Cmd(0x0D);
}

• Display ON, blinking OFF, cursor visible.

void Lcd4_DisplayON_BlinkON_CursorOFF() {
  Lcd4_Cmd(0x00);
  Lcd4_Cmd(0x0E);
}

• Display ON, blinking ON, cursor hidden.

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c) Shift Commands (Commented Out)

// void Lcd4_Shift_Left() { Lcd4_Cmd(0x01); Lcd4_Cmd(0x08); }
// void Lcd4_Shift_Right() { Lcd4_Cmd(0x01); Lcd4_Cmd(0x0C); }

• 0x18 → Shift display left
• 0x1C → Shift display right

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How It Works

1. Lcd4_Cmd() sends commands to the LCD. In 4-bit mode, each byte is split into upper and lower nibble.
2. Functions like Lcd4_Clear() or Lcd4_DisplayON_BlinkOFF_CursorON() wrap these commands for easier use in code.
3. By calling these functions, you can control display on/off, cursor visibility, blinking, and clear or shift the display.