C Library for HD44780 LCD driver

HD44780 Description

Detailed information is in HD44780 Datasheet.

Hardware connection

PORT LCD	PORT ATMEGA16A	Description
USS	GND	Ground
UDD	+5V	Supply Voltage
U0	Potentiometer	Contrast Adjustment
RS	PORTD 1	Data/Instruction Select
RW	PORTD 2	Read/Write Select
E	PORTD 3	Enable Signal
D4	PORTD 4	Data bit 4
D5	PORTD 5	Data bit 5
D6	PORTD 6	Data bit 6
D7	PORTD 7	Data bit 7

Library

Library is aimed for MCU ATmega16 / Atmega8 which supports 4-bit Operation.

Tested

Library was tested and proved on a 16x2 LCD Display with Atmega16.

Usage

Prior defined for:

• Atmega16 / Atmega8
• LCD 16x2

Initializing 4-bit operation

Initializing LCD Driver HD44780 according to Figure 24 in HD44780 Datasheet.

// +---------------------------+
// |         Power on          |
// | Wait for more than 15 ms  |   // 15 ms wait
// | after VCC rises to 4.5 V  |
// +---------------------------+
//              |
// +---------------------------+ 
// |  RS R/W DB7 DB6 DB5 DB4   |
// |   0   0   0   0   1   1   |   // Initial sequence 0x30
// | Wait for more than 4.1 ms |   // 4.1 ms us writing DATA into DDRAM or CGRAM
// +---------------------------+
//              |
// +---------------------------+
// |  RS R/W DB7 DB6 DB5 DB4   |
// |   0   0   0   0   1   1   |   // Initial sequence 0x30
// | Wait for more than 0.1 ms |   // 100 us writing DATA into DDRAM or CGRAM
// +---------------------------+
//              |
// +---------------------------+   // Initial sequence 0x30
// |  RS R/W DB7 DB6 DB5 DB4   |   // 37 us writing DATA into DDRAM or CGRAM
// |   0   0   0   0   1   1   |   // 4us tadd - time after BF disapeared
// | Wait for more than 45 us  |   // 37 us + 4 us = 41 us * (270/250) = 45us
// +---------------------------+
//              |
// +---------------------------+   // 4bit mode 0x20
// |  RS R/W DB7 DB6 DB5 DB4   |   // 37 us writing DATA into DDRAM or CGRAM
// |   0   0   0   0   1   0   |   // 4us tadd - time after BF disapeared
// | Wait for more than 45 us  |   // !!! BUSY FLAG CHECK DOESN'T WORK CORRECTLY !!!
// +---------------------------+
//              |
// +---------------------------+
// |  RS R/W DB7 DB6 DB5 DB4   |   // Display off 0x08
// |   0   0   0   0   0   0   |   // 
// |   0   0   1   0   0   0   |   // 
// |    Wait for BF Cleared    |   // Wait for BF Cleared
// +---------------------------+
//              |
// +---------------------------+
// |  RS R/W DB7 DB6 DB5 DB4   |   // Display clear 0x01
// |   0   0   0   0   0   0   |   //
// |   0   0   0   0   0   1   |   //
// |    Wait for BF Cleared    |   // Wait for BF Cleared
// +---------------------------+
//              |
// +---------------------------+
// |  RS R/W DB7 DB6 DB5 DB4   |   // Entry mode set 0x06
// |   0   0   0   0   0   0   |   // 
// |   0   0   0   1   1   0   |   // shift cursor to the left, without text shifting
// |    Wait for BF Cleared    |   // Wait for BF Cleared
// +---------------------------+

Functions

• HD44780_Init() - init display
• HD44780_DisplayClear() - clear display and set position to 0, 0
• HD44780_DisplayOn() - turn on display
• HD44780_CursorOn() - turn on cursor
• HD44780_CursorOff() - turn off cursor
• HD44780_CursorBlink() - blink the cursor blink
• HD44780_DrawChar(char) - draw character on display
• HD44780_DrawString(char *) - draw string
• HD44780_PositionXY(char, char) - set position X, Y
• HD44780_Shift(char, char) - shift cursor or display to left or right

HD44780_Init

void HD44780_Init (void)

Base initialisation function. If the electrical characteristics conditions listed under the table Power Supply Conditions Using Internal Reset Circuit are not met, the internal reset circuit will not operate normally and will fail to initialize the HD44780U. For such a case, initialization must be performed by the MPU as explained in the section 4-bit Operation or 8-bit Operation depending on mode.

HD44780_DisplayClear

void HD44780_DisplayClear (void)

Display clear and set cursor to position 0, 0.

HD44780_DisplayOn

void HD44780_DisplayOn (void)

Turn on the display.

HD44780_CursorOn

void HD44780_CursorOn (void)

Turn on the cursor. Cursor will be visible. IMPORTANT: Function HD44780_CursorOn() besides the cursor on, switches the display on, so don't need to use function HD44780_DisplayOn(). But without function HD44780_CursorOn() display is switched on by the function HD44780_DisplayOn().

HD44780_CursorOff

void HD44780_CursorOff (void)

Turn off the cursor. Cursor will be hide but display will be on.

HD44780_CursorBlink

void HD44780_CursorBlink (void)

Turn the cursor blink. Cursor will be visible and it will blink. IMPORTANT: Function HD44780_CursorBlink() besides the cursor blink, switches the display on, so don't need to use function HD44780_DisplayOn(). But without function HD44780_CursorBlink() display is switched on by the function HD44780_DisplayOn().

HD44780_DrawChar

void HD44780_DrawChar (char character)

Draw specific char on display according to ASCII table.

HD44780_DrawString

void HD44780_DrawString (char *str)

Draw string.

HD44780_PositionXY

char HD44780_PositionXY (char x, char y)

Set DDRAM or CGRAM at the specific position X, Y. For LCD 16x2 (cols, rows) maximal possible values:

• X from interval values {0; 1; ... 15},
• Y from interval values {0; 1}.

HD44780_Shift

char HD44780_Shift (char item, char direction)

Shift cursor or display to left or right. Item defines either cursor or display we want to move. Two possible values for item are defined:

• HD44780_CURSOR,
• HD44780_DISPLAY.

The second parameter is direction definition. Two possible values for direction are defined:

• HD44780_RIGHT,
• HD44780_LEFT.

Demonstration

Links

• HD44780 Datasheet