#include <avr/io.h>
#include <util/delay.h>
#include <stdlib.h>
//write 0 read 1
//command 0 data 1
#define lcd_data PORTD
#define lcd_data_dir DDRD
#define lcd_ctrl PORTB
#define lcd_ctrl_dir DDRB
#define RS PB1
#define RW PB2
#define EN PB3
//set position array
uint8_t position_y[2] = {0,64};
//function prototypes
void peekaboo(void);
void checkbusy(void);
void send_command(unsigned char command);
void send_data(unsigned char data);
void send_string(char *string);
void set_cursor(uint8_t x,uint8_t y);

int main(void)
{
  lcd_ctrl_dir |= 1 << RS | 1 << RW | 1 << EN;
  _delay_ms(15);

  send_command(0x01);    //clear lcd
  _delay_ms(2);
  send_command(0x38);    //8-bit mode line-2 5x7 dots
  _delay_ms(50);
  send_command(0x0E);     //display on cursor on
  _delay_ms(50);

  char positionstring[2];

  while(1)
  {
    for(int y=0;y<2;y++)
    {
      for(int x=0;x<16;x++)
      {
        itoa(x,positionstring,10);
        set_cursor(7,0);
        send_string("X = ");
        send_string(positionstring);
        itoa(y,positionstring,10);
        set_cursor(7,1);
        send_string("Y = ");
        send_string(positionstring);
        set_cursor(x,y);
        send_string("x");
        _delay_ms(400);
        set_cursor(x,y);
        send_string(" ");
        itoa(x,positionstring,10);
        set_cursor(7,0);
        send_string("      ");
        itoa(y,positionstring,10);
        set_cursor(7,1);
        send_string("      ");
      }
    }
  }
  return 0;
}

void peekaboo(void)
{
  lcd_ctrl |= 1 << EN;
  asm volatile("nop");
  asm volatile("nop");
  lcd_ctrl &= ~(1 << EN);
}

void checkbusy(void)
{
  lcd_data_dir = 0;
  lcd_ctrl |= (1 << RW);
  lcd_ctrl &= ~(1 << RS);
  while(lcd_data >= 0x80)
  {
    peekaboo();
  }
  lcd_data_dir = 0xFF;
}

void send_command(unsigned char command)
{
  checkbusy();
  lcd_data = command;
  lcd_ctrl &= ~(1 << RW | 1 << RS);
  peekaboo();
  lcd_data = 0;
}

void send_data(unsigned char data)
{
  checkbusy();
  lcd_data = data;
  lcd_ctrl |= (1 << RS);
  lcd_ctrl &= ~(1 << RW);
  peekaboo();
  lcd_data = 0;
}

void send_string(char *string)
{
  while(*string > 0)       //*string != NULL
  {
    send_data(*string++);
  }
}

void set_cursor(uint8_t x,uint8_t y)
{
  send_command(0x80 + position_y[y] + x);
}