/****************************************************************************
    LCD-AVR-8f.c  - Use an HD44780U based LCD with an Atmel ATmega processor
 
    Copyright (C) 2013 Donald Weiman    (weimandn@alfredstate.edu)
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.
 
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/
/****************************************************************************
         File:    LCD-AVR-8f.c
         Date:    September 16, 2013
 
       Target:    ATmega328
     Compiler:    avr-gcc (AVR Studio 6)
       Author:    Donald Weiman
 
      Summary:    8-bit data interface, with busy flag implemented
                  Any LCD pin can be connected to any available I/O port
                  Includes a simple write string routine.
*/
/******************************* Program Notes ******************************
 
            This program uses an 8-bit data interface and it uses the busy 
              flag to determine when the LCD controller is ready.  The LCD 
              RW line (pin 5) must therefore be connected to the uP.
 
            The use of the busy flag does not mean that all of the software 
              time delays have been eliminated.  There are still several 
              required in the LCD initialization routine where the busy flag  
              cannot yet be used.  These delays are have been implemented at 
              least twice as long as called for in the data sheet to 
              accommodate some of the out of spec displays that may show up.  
              There are also some other software time delays required to 
              implement timing requirements such as setup and hold times for 
              the various control signals.
 
  ***************************************************************************
 
            The eight data lines as well as the three control lines may be
              implemented on any available I/O pin of any port.  These are
              the connections used for this program:
 
                 -----------                   ----------
                | ATmega328 |                 |   LCD    |
                |           |                 |          |
                |        PD7|---------------->|D7        |
                |        PD6|---------------->|D6        |
                |        PD5|---------------->|D5        |
                |        PD4|---------------->|D4        |
                |        PD3|---------------->|D3        |
                |        PD2|---------------->|D2        |
                |        PD1|---------------->|D1        |
                |        PD0|---------------->|D0        |
                |           |                 |          |
                |        PB1|---------------->|E         |
                |        PB2|---------------->|RW        |
                |        PB0|---------------->|RS        |
                 -----------                   ----------
 
  **************************************************************************/

#define F_CPU 16000000UL

#include <avr/io.h>
#include <util/delay.h>

// LCD interface (should agree with the diagram above)
#define lcd_D7_port     PORTD                   // lcd D7 connection
#define lcd_D7_bit      PORTD7
#define lcd_D7_ddr      DDRD
#define lcd_D7_pin      PIND                    // busy flag

#define lcd_D6_port     PORTD                   // lcd D6 connection
#define lcd_D6_bit      PORTD6
#define lcd_D6_ddr      DDRD

#define lcd_D5_port     PORTD                   // lcd D5 connection
#define lcd_D5_bit      PORTD5
#define lcd_D5_ddr      DDRD

#define lcd_D4_port     PORTD                   // lcd D4 connection
#define lcd_D4_bit      PORTD4
#define lcd_D4_ddr      DDRD

#define lcd_D3_port     PORTD                   // lcd D3 connection
#define lcd_D3_bit      PORTD3
#define lcd_D3_ddr      DDRD

#define lcd_D2_port     PORTD                   // lcd D2 connection
#define lcd_D2_bit      PORTD2
#define lcd_D2_ddr      DDRD

#define lcd_D1_port     PORTD                   // lcd D1 connection
#define lcd_D1_bit      PORTD1
#define lcd_D1_ddr      DDRD

#define lcd_D0_port     PORTD                   // lcd D0 connection
#define lcd_D0_bit      PORTD0
#define lcd_D0_ddr      DDRD

#define lcd_E_port      PORTB                   // lcd Enable pin
#define lcd_E_bit       PORTB1
#define lcd_E_ddr       DDRB

#define lcd_RS_port     PORTB                   // lcd Register Select pin
#define lcd_RS_bit      PORTB0
#define lcd_RS_ddr      DDRB

#define lcd_RW_port     PORTB                   // lcd Read/Write pin
#define lcd_RW_bit      PORTB2
#define lcd_RW_ddr      DDRB

// LCD module information
#define lcd_LineOne     0x00                    // start of line 1
#define lcd_LineTwo     0x40                    // start of line 2
//#define   lcd_LineThree   0x14                  // start of line 3 (20x4)
//#define   lcd_lineFour    0x54                  // start of line 4 (20x4)
//#define   lcd_LineThree   0x10                  // start of line 3 (16x4)
//#define   lcd_lineFour    0x50                  // start of line 4 (16x4)

// LCD instructions
#define lcd_Clear           0b00000001          // replace all characters with ASCII 'space'
#define lcd_Home            0b00000010          // return cursor to first position on first line
#define lcd_EntryMode       0b00000110          // shift cursor from left to right on read/write
#define lcd_DisplayOff      0b00001000          // turn display off
#define lcd_DisplayOn       0b00001100          // display on, cursor off, don't blink character
#define lcd_FunctionReset   0b00110000          // reset the LCD
#define lcd_FunctionSet8bit 0b00111000          // 8-bit data, 2-line display, 5 x 7 font
#define lcd_SetCursor       0b10000000          // set cursor position

// Program ID
uint8_t program_author[]   = "Donald Weiman";
uint8_t program_version[]  = "LCD-AVR-8f (gcc)";
uint8_t program_date[]     = "Sep 16, 2013";

// Function Prototypes
void lcd_write_8(uint8_t);
void lcd_write_instruction_8f(uint8_t);
void lcd_write_character_8f(uint8_t);
void lcd_write_string_8f(uint8_t *);
void lcd_init_8f(void);
void lcd_check_BF_8(void);

/******************************* Main Program Code *************************/
int main(void)
{
// configure the microprocessor pins for the data lines
    lcd_D7_ddr |= (1<<lcd_D7_bit);                  // 8 data lines - output
    lcd_D6_ddr |= (1<<lcd_D6_bit);
    lcd_D5_ddr |= (1<<lcd_D5_bit);
    lcd_D4_ddr |= (1<<lcd_D4_bit);
    lcd_D3_ddr |= (1<<lcd_D3_bit);
    lcd_D2_ddr |= (1<<lcd_D2_bit);
    lcd_D1_ddr |= (1<<lcd_D1_bit);
    lcd_D0_ddr |= (1<<lcd_D0_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);                  // RW line - output 

// initialize the LCD controller as determined by the defines (LCD instructions)
    lcd_init_8f();                                  // initialize the LCD display for an 8-bit interface

// display the first line of information
    lcd_write_string_8f(program_author);

// set cursor to start of second line
    lcd_check_BF_8();                               // make sure LCD controller is ready
    lcd_write_instruction_8f(lcd_SetCursor | lcd_LineTwo);

// display the second line of information
    lcd_write_string_8f(program_version);

// endless loop
    while(1);
    return 0;
}
/******************************* End of Main Program Code ******************/

/*============================== 8-bit LCD Functions ======================*/
/*
  Name:     lcd_init_8f
  Purpose:  initialize the LCD module for a 8-bit data interface
  Entry:    equates (LCD instructions) set up for the desired operation
  Exit:     no parameters
  Notes:    uses the busy flag instead of time delays when possible
*/
void lcd_init_8f(void)
{
// Power-up delay
    _delay_ms(100);                                 // initial 40 mSec delay

// Reset the LCD controller
    lcd_write_instruction_8f(lcd_FunctionReset);    // first part of reset sequence
    _delay_ms(10);                                  // 4.1 mS delay (min)

    lcd_write_instruction_8f(lcd_FunctionReset);    // second part of reset sequence
    _delay_us(200);                                 // 100uS delay (min)

    lcd_write_instruction_8f(lcd_FunctionReset);    // third part of reset sequence
    _delay_us(200);                                 // this delay is omitted in the data sheet

// Function Set instruction
    lcd_write_instruction_8f(lcd_FunctionSet8bit);  // set mode, lines, and font
// --> from this point on the busy flag is available <--       

// 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_check_BF_8();                               // make sure LCD controller is ready
    lcd_write_instruction_8f(lcd_DisplayOff);       // turn display OFF

// Clear Display instruction
    lcd_check_BF_8();                               // make sure LCD controller is ready
    lcd_write_instruction_8f(lcd_Clear);            // clear display RAM

// ; Entry Mode Set instruction
    lcd_check_BF_8();                               // make sure LCD controller is ready
    lcd_write_instruction_8f(lcd_EntryMode);        // set desired shift characteristics

// 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_check_BF_8();                               // make sure LCD controller is ready
    lcd_write_instruction_8f(lcd_DisplayOn);        // turn the display ON
}

/*...........................................................................
  Name:     lcd_write_string_8f
; Purpose:  display a string of characters on the LCD
  Entry:    (theString) is the string to be displayed
  Exit:     no parameters
  Notes:    uses the busy flag instead of time delays 
*/
void lcd_write_string_8f(uint8_t theString[])
{
    volatile int i = 0;                             // character counter*/
    while (theString[i] != 0)
    {
        lcd_check_BF_8();                           // make sure LCD controller is ready    
        lcd_write_character_8f(theString[i]);
        i++;
    }
}

/*...........................................................................
  Name:     lcd_write_character_8f
  Purpose:  send a byte of information to the LCD data register
  Entry:    (theData) is the information to be sent to the data register
  Exit:     no parameters
  Notes:    configures RW (busy flag is implemented)
*/
void lcd_write_character_8f(uint8_t theData)
{
    lcd_RW_port &= ~(1<<lcd_RW_bit);                // write to LCD module (RW low)
    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_8(theData);                           // write the data
}

/*...........................................................................
  Name:     lcd_write_instruction_8f
  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:    configures RW (busy flag is implemented)
*/
void lcd_write_instruction_8f(uint8_t theInstruction)
{
    lcd_RW_port &= ~(1<<lcd_RW_bit);                // write to LCD module (RW low)
    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_8(theInstruction);                    // write the instruction
}


/*...........................................................................
  Name:     lcd_write_8
  Purpose:  send a byte of information to the LCD module
  Entry:    (theByte) is the information to be sent to the desired LCD register
            RS is configured for the desired LCD register
            E is low
            RW is low
  Exit:     no parameters
  Notes:    use either time delays or the busy flag
*/
void lcd_write_8(uint8_t theByte)
{
    lcd_D7_port &= ~(1<<lcd_D7_bit);                        // assume that data is '0'
    if (theByte & 1<<7) lcd_D7_port |= (1<<lcd_D7_bit);     // make data = '1' if necessary 

    lcd_D6_port &= ~(1<<lcd_D6_bit);                        // repeat for each data bit
    if (theByte & 1<<6) lcd_D6_port |= (1<<lcd_D6_bit);

    lcd_D5_port &= ~(1<<lcd_D5_bit);
    if (theByte & 1<<5) lcd_D5_port |= (1<<lcd_D5_bit);

    lcd_D4_port &= ~(1<<lcd_D4_bit);
    if (theByte & 1<<4) lcd_D4_port |= (1<<lcd_D4_bit);

    lcd_D3_port &= ~(1<<lcd_D3_bit);
    if (theByte & 1<<3) lcd_D3_port |= (1<<lcd_D3_bit);

    lcd_D2_port &= ~(1<<lcd_D2_bit);
    if (theByte & 1<<2) lcd_D2_port |= (1<<lcd_D2_bit);

    lcd_D1_port &= ~(1<<lcd_D1_bit);
    if (theByte & 1<<1) lcd_D1_port |= (1<<lcd_D1_bit);

    lcd_D0_port &= ~(1<<lcd_D0_bit);
    if (theByte & 1<<0) lcd_D0_port |= (1<<lcd_D0_bit);

// write the data
                                                    // 'Address set-up time' (40 nS)
    lcd_E_port |= (1<<lcd_E_bit);                   // Enable pin high
    _delay_us(1);                                   // implement 'Data set-up time' (80 nS) and 'Enable pulse width' (230 nS)
    lcd_E_port &= ~(1<<lcd_E_bit);                  // Enable pin low
    _delay_us(1);                                   // implement 'Data hold time' (10 nS) and 'Enable cycle time' (500 nS)
}

/*...........................................................................
  Name:     lcd_check_BF_8
  Purpose:  check busy flag, wait until LCD is ready
  Entry:    no parameters
  Exit:     no parameters
  Notes:    main program will hang if LCD module is defective or missing
            data is read while 'E' is high
*/
void lcd_check_BF_8(void)
{
    uint8_t busy_flag_copy;                         // busy flag 'mirror'

    lcd_D7_ddr &= ~(1<<lcd_D7_bit);                 // set D7 data direction to input
    lcd_RS_port &= ~(1<<lcd_RS_bit);                // select the Instruction Register (RS low)
    lcd_RW_port |= (1<<lcd_RW_bit);                 // read from LCD module (RW high)

    do
    {
        busy_flag_copy = 0;                         // initialize busy flag 'mirror'
        lcd_E_port |= (1<<lcd_E_bit);               // Enable pin high
        _delay_us(1);                               // implement 'Delay data time' (160 nS) and 'Enable pulse width' (230 nS)

        busy_flag_copy |= (lcd_D7_pin & (1<<lcd_D7_bit));  // get actual busy flag status

        lcd_E_port &= ~(1<<lcd_E_bit);              // Enable pin low
        _delay_us(1);                               // implement 'Address hold time' (10 nS), 'Data hold time' (10 nS), and 'Enable cycle time' (500 nS )
        
    } while (busy_flag_copy);                       // check again if busy flag was high

// arrive here if busy flag is clear -  clean up and return 
    lcd_RW_port &= ~(1<<lcd_RW_bit);                // write to LCD module (RW low)       <-- (not really necessary)
    lcd_D7_ddr |= (1<<lcd_D7_bit);                  // reset D7 data direction to output
}