/*...........................................................................
Name: lcd_write_instruction_4d
Purpose: send a byte of information to the LCD instruction register
Entry: (theInstruction) is the information to be sent to the instruction register
Exit: no parameters
Notes: does not deal with RW (busy flag is not implemented)
*/
void lcd_write_instruction_4d(uint8_t theInstruction)
{
lcd_RS_port &= ~(1<<lcd_RS_bit); // select the Instruction Register (RS low)
lcd_E_port &= ~(1<<lcd_E_bit); // make sure E is initially low
lcd_write_4(theInstruction); // write the upper 4-bits of the data
lcd_write_4(theInstruction << 4); // write the lower 4-bits of the data
}
void lcd_write_character_4d(uint8_t theData)
{
lcd_RS_port |= (1<<lcd_RS_bit); // select the Data Register (RS high)
lcd_E_port &= ~(1<<lcd_E_bit); // make sure E is initially low
lcd_write_4(theData); // write the upper 4-bits of the data
lcd_write_4(theData << 4); // write the lower 4-bits of the data
}
/*
Name: lcd_init_4d
Purpose: initialize the LCD module for a 4-bit data interface
Entry: equates (LCD instructions) set up for the desired operation
Exit: no parameters
Notes: uses time delays rather than checking the busy flag
*/
void lcd_init_4d(void)
{
// Power-up delay
_delay_ms(100); // initial 100 mSec delay
// Set up the RS and E lines for the 'lcd_write_4' subroutine.
lcd_RS_port &= ~(1<<lcd_RS_bit); // select the Instruction Register (RS low)
lcd_E_port &= ~(1<<lcd_E_bit); // make sure E is initially low
// Reset the LCD controller
lcd_write_4(lcd_FunctionSet8bit); // first part of reset sequence
_delay_ms(10); // 4.1 mS delay (min)
lcd_write_4(lcd_FunctionSet8bit); // second part of reset sequence
_delay_us(200); // 100uS delay (min)
lcd_write_4(lcd_FunctionSet8bit); // third part of reset sequence
_delay_us(200); // this delay is omitted in the data sheet
lcd_write_4(lcd_functionSet4bit); // set 4-bit mode
_delay_us(5); // 40uS delay (min)
// Function Set instruction
lcd_write_instruction_4d(lcd_functionSet4bit); // set mode, lines, and font
_delay_us(40); // 40uS delay (min)
// Clear Display instruction
lcd_write_instruction_4d(lcd_clear); // clear display RAM
_delay_ms(5); // 1.64 mS delay (min)
// Display On/Off Control instruction
lcd_write_instruction_4d(lcd_displayOn); // turn the display ON
_delay_us(40); // 40uS delay (min)
// ; Entry Mode Set instruction
lcd_write_instruction_4d(lcd_entryMode); // set desired shift characteristics
_delay_us(40); // 40uS delay (min)
}
/*
Name: lcd_init_4d
Purpose: initialize the LCD module for a 4-bit data interface
Entry: equates (LCD instructions) set up for the desired operation
Exit: no parameters
Notes: uses time delays rather than checking the busy flag
*/
void lcd_init_4d(void)
{
// configure the microprocessor pins for the data lines
lcd_D7_ddr |= (1<<lcd_D7_bit); // 4 data lines - output
lcd_D6_ddr |= (1<<lcd_D6_bit);
lcd_D5_ddr |= (1<<lcd_D5_bit);
lcd_D4_ddr |= (1<<lcd_D4_bit);
// configure the microprocessor pins for the control lines
lcd_E_ddr |= (1<<lcd_E_bit); // E line - output
lcd_RS_ddr |= (1<<lcd_RS_bit); // RS line - output
// lcd_RW_ddr |= (1<<lcd_RW_bit); // RS line - output
// lcd_RW_port &= ~(1<<lcd_RW_bit);
// Power-up delay
_delay_ms(100); // initial 40 mSec delay
// IMPORTANT - At this point the LCD module is in the 8-bit mode and it is expecting to receive
// 8 bits of data, one bit on each of its 8 data lines, each time the 'E' line is pulsed.
//
// Since the LCD module is wired for the 4-bit mode, only the upper four data lines are connected to
// the microprocessor and the lower four data lines are typically left open. Therefore, when
// the 'E' line is pulsed, the LCD controller will read whatever data has been set up on the upper
// four data lines and the lower four data lines will be high (due to internal pull-up circuitry).
//
// Fortunately the 'FunctionReset' instruction does not care about what is on the lower four bits so
// this instruction can be sent on just the four available data lines and it will be interpreted
// properly by the LCD controller. The 'lcd_write_4' subroutine will accomplish this if the
// control lines have previously been configured properly.
// Set up the RS and E lines for the 'lcd_write_4' subroutine.
lcd_RS_port &= ~(1<<lcd_RS_bit); // select the Instruction Register (RS low)
lcd_E_port &= ~(1<<lcd_E_bit); // make sure E is initially low
// Reset the LCD controller
lcd_write_4(lcd_FunctionReset); // first part of reset sequence
_delay_ms(10); // 4.1 mS delay (min)
lcd_write_4(lcd_FunctionReset); // second part of reset sequence
_delay_us(200); // 100uS delay (min)
lcd_write_4(lcd_FunctionReset); // third part of reset sequence
_delay_us(200); // this delay is omitted in the data sheet
// Preliminary Function Set instruction - used only to set the 4-bit mode.
// The number of lines or the font cannot be set at this time since the controller is still in the
// 8-bit mode, but the data transfer mode can be changed since this parameter is determined by one
// of the upper four bits of the instruction.
lcd_write_4(lcd_FunctionSet4bit); // set 4-bit mode
_delay_us(80); // 40uS delay (min)
// Function Set instruction
lcd_write_instruction_4d(lcd_FunctionSet4bit); // set mode, lines, and font
_delay_us(80); // 40uS delay (min)
// The next three instructions are specified in the data sheet as part of the initialization routine,
// so it is a good idea (but probably not necessary) to do them just as specified and then redo them
// later if the application requires a different configuration.
// Display On/Off Control instruction
lcd_write_instruction_4d(lcd_DisplayOff); // turn display OFF
_delay_us(80); // 40uS delay (min)
// Clear Display instruction
lcd_write_instruction_4d(lcd_Clear); // clear display RAM
_delay_ms(4); // 1.64 mS delay (min)
// ; Entry Mode Set instruction
lcd_write_instruction_4d(lcd_EntryMode); // set desired shift characteristics
_delay_us(80); // 40uS delay (min)
// This is the end of the LCD controller initialization as specified in the data sheet, but the display
// has been left in the OFF condition. This is a good time to turn the display back ON.
// Display On/Off Control instruction
lcd_write_instruction_4d(lcd_DisplayOn); // turn the display ON
_delay_us(80); // 40uS delay (min)
lcd_write_instruction_4d(lcd_Home);
_delay_ms(10);
}
