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

#define rs PC0
#define en PC1
#define D4 PC2
#define D5 PC3
#define D6 PC4
#define D7 PC5

char column[2] = {0,64};

void lcd_command(unsigned char command)
{
  PORTC = (PORTC & 0x03) | ((command & 0xF0) >> 2);
  PORTC &= ~(1 << rs);
  PORTC |= (1 << en);
  _delay_ms(1);
  PORTC &= ~(1 << en);
  _delay_ms(200);
  PORTC = (PORTC & 0x03) | ((command & 0x0F) << 2);
  PORTC |= (1 << en);
  _delay_ms(1);
  PORTC &= ~(1 << en);
  _delay_ms(2);
}

void lcd_data(unsigned char data)
{
  PORTC = (PORTC & 0x03) | ((data & 0xF0) >> 2);
  PORTC |= (1 << rs);
  PORTC |= (1 << en);
  _delay_ms(1);
  PORTC &= ~(1 << en);
  _delay_ms(200);
  PORTC = (PORTC & 0x03) | ((data & 0x0F) << 2);
  PORTC |= (1 << en);
  _delay_ms(1);
  PORTC &= ~(1 << en);
  _delay_ms(2);
}

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

void lcd_init(void)
{
  DDRC |= (1 << rs) | (1 << en) | (1 << D4) | (1 << D5) | (1 << D6) | (1 << D7);
  _delay_ms(20);
  lcd_command(0x33);
  lcd_command(0x32);
  lcd_command(0x28);
  lcd_command(0x0C);
  lcd_command(0x06);
  lcd_command(0x01);
  _delay_ms(2);
}

void send_string(char *string)
{
  while(*string != '\0')
  {
    lcd_data(*string++);
  }
}

void lcd_clear(void)
{
  lcd_command(0x01);
  _delay_ms(2);
}

void spi_init(void)
{
  DDRD |= (1 << PD2) | (1 << PD5) | (1 << PD7);
  SPCR |= (1 << SPE) | (1 << SPR0) | (1 << MSTR);
}

uint8_t spi_transfer(uint8_t data)
{
  SPDR = data;
  while(!(SPSR & (1 << SPIF)));
  return SPDR;
}

void setpotent(uint8_t value)
{
  PORTD &= ~(1 << PD5);
  spi_transfer(0x13);
  spi_transfer(value);
  PORTD |= (1 << PD5);
}

volatile int8_t encodervalue = 0;
volatile uint8_t potvalue = 64;

void encoder_init(void)
{
  DDRD &= ~((1 << PD2) | (1 << PD3));
  PORTD |= (1 << PD2) | (1 << PD3);

  EICRA |= (1 << ISC10) | (1 << ISC00);
  EIMSK |= (1 << INT1) | (1 << INT0);
  sei();
}

ISR(INT1_vect)
{
  static uint8_t laststate = 0;
  uint8_t currentstate = (PIND & ((1 << PD2) | (1 << PD3)));

  if(currentstate != laststate)
  {
    laststate = currentstate;
  }

  if((currentstate & (1 << PD2)) == ((currentstate & (1 << PD3)) >> 1))
  {
    encodervalue++;
    if(potvalue < 127)
    {
      potvalue++;
    }
    else
    {
      encodervalue--;
      if(potvalue > 0)
      {
        potvalue--;
      }
    }
  }
}

ISR(INT0_vect)
{
  static uint8_t laststate = 0;
  uint8_t currentstate = (PIND & ((1 << PD2) | (1 << PD3)));

  if(currentstate != laststate)
  {
    laststate = currentstate;
  }

  if((currentstate & (1 << PD2)) == ((currentstate & (1 << PD3)) >> 1))
  {
    encodervalue--;
    if(potvalue > 0)
    {
      potvalue--;
    }
    else
    {
      encodervalue++;
      if(potvalue < 127)
      {
        potvalue++;
      }
    }
  }
}

void lcd_number(uint8_t number)
{
  char buffer[4];
  if(number < 10)
  {
    buffer[0] = '0' + number;
    buffer[1] = '\0';
  } else if(number < 100)
  {
    buffer[0] = '0' + number/10;
    buffer[1] = '0' + number%10;
    buffer[2] = '\0';
  }else
  {
    buffer[0] = '0' + number/100;
    buffer[1] = '0' + (number/10)%10;
    buffer[2] = '0' + number%10;
    buffer[3] = '\0';
  }
  send_string(buffer);
}

int main(void)
{
  lcd_init();
  spi_init();
  encoder_init();

  send_string("digital potent = ");
  lcd_command(0xC0);
  send_string("value = ");

  while(1)
  {
    setpotent(potvalue);
    lcd_command(0xC8);
    lcd_number(potvalue);
    _delay_ms(100);
  }
  return 0;
}