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

volatile uint8_t adc_result = 0;

#define RS PD0
#define EN PD1
#define D4 PD2
#define D5 PD3
#define D6 PD4
#define D7 PD5

uint8_t column_y[2] = {0,64};

void lcd_init(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);
void adc_init(void);
void start_conversion(void);
void send_adc(uint8_t result);

int main(void)
{
  lcd_init();
  adc_init();
  start_conversion();
  while(1)
  {
    send_adc(adc_result);
  }
  return 0;
}

void lcd_init(void)
{
  DDRD |= (1 << RS) | (1 << EN) | (1 << D4) | (1 << D5) | (1 << D6) | (1 << D7);
  _delay_ms(20);
  send_command(0x33);
  send_command(0x32);
  send_command(0x28);
  send_command(0x0C);
  send_command(0x06);
  send_command(0x01);
  _delay_ms(2);
}

void send_command(unsigned char command)
{
  PORTD = ((PORTD & 0x03) | ((command & 0xF0) >> 2));
  PORTD &= ~(1 << RS);
  PORTD |= (1 << EN);
  _delay_ms(1);
  PORTD &= ~(1 << EN);
  _delay_ms(200);
  PORTD = ((PORTD & 0x03) | ((command & 0x0F) << 2));
  PORTD |= (1 << EN);
  _delay_ms(1);
  PORTD &= ~(1 << EN);
  _delay_ms(2);
}

void send_data(unsigned char data)
{
   PORTD = ((PORTD & 0x03) | ((data & 0xF0) >> 2));
  PORTD |= (1 << RS);
  PORTD |= (1 << EN);
  _delay_ms(1);
  PORTD &= ~(1 << EN);
  _delay_ms(200);
  PORTD = ((PORTD & 0x03) | ((data & 0x0F) << 2));
  PORTD |= (1 << EN);
  _delay_ms(1);
  PORTD &= ~(1 << EN);
  _delay_ms(2);
}

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

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

void adc_init(void)
{
  ADMUX |= (1 << REFS0);
  ADCSRA |= (1 << ADEN) | (1 << ADPS2) | (1 << ADPS1) | (1 << ADPS0) | (1 << ADIE);
  DIDR0 |= (1 << ADC0D);
  sei();
}

void start_conversion(void)
{
  ADCSRA |= (1 << ADSC);
}

void send_adc(uint8_t result)
{
  char buffer[16];
  set_cursor(0,0);
  itoa(result,buffer,10);
  send_string(buffer);
}

ISR(ADC_vect)
{
  //uint16_t value = ADCH << 2 | ADCL >> 6;
  adc_result = ADC;
  start_conversion();
}