#include <stdbool.h>
#include <avr/io.h>
#include <avr/interrupt.h>
#define F_CPU 20000000UL  //20 MHz
#include <util/delay.h>

/* 7-Segment display: */
#define NUM_DIGITS 3U  //3 Digits
#define DIGIT_TENS 2U  //left
#define DIGIT_ONES 1U  //middle
#define DIGIT_UNIT 0U  //right
#define SELECT_DIGIT(digit) (1U << digit)

#define TEMP_MIN 0U
#define TEMP_MAX 50U

#define BUTTON_THRESHOLD 50U //software debounce

/* Symbol indexes: */
#define SYM_n           10U
#define SYM_o           11U
#define SYM_E           12U
#define SYM_R           13U
#define SYM_DEG_CELCIUS 14U
#define SYM_P_P         15U
#define SYM_OFF         16U
#define SYM_DASH        17U

/*
 7-Segment Layout:

     A
  F     B
     G  
  E     C
     D    P

 Pin       7  6  5  4  3  2  1  0
 Segment   A  F  B  E  D  C  G  P
*/
static uint8_t g_au8Symbols[18U] =
{
/* 00 */ 0b11111100U, //0 (ABCDEF)
/* 01 */ 0b00100100U, //1 (BC)
/* 02 */ 0b10111010U, //2 (ABDEG)
/* 03 */ 0b10101110U, //3 (ABCDG)
/* 04 */ 0b01100110U, //4 (BCFG)
/* 05 */ 0b11001110U, //5 (ACDFG)
/* 06 */ 0b11011110U, //6 (ACDEFG)
/* 07 */ 0b10100100U, //7 (ABC)
/* 08 */ 0b11111110U, //8 (ABCDEFG)
/* 09 */ 0b11101110U, //9 (ABCDFG)
/* 10 */ 0b00010110U, //n (CEG)      SYM_n
/* 11 */ 0b00011110U, //o (CDEG)     SYM_o
/* 12 */ 0b11011010U, //E (ADEFG)    SYM_E
/* 13 */ 0b00010010U, //r (EG)       SYM_r
/* 14 */ 0b10101101U, //degC (ABCDP) SYM_DEG_CELCIUS
/* 15 */ 0b11110011U, //P. (ABEFGP)  SYM_P_P
/* 16 */ 0b00000000U, //OFF          SYM_OFF
/* 17 */ 0b00000010U  //- (G)        SYM_DASH
};

static uint8_t g_u8WaterTemperature = 24U;   //Water temperature, default 24 degree celcius
static uint8_t g_u8CountIncs = 0U;           //'+' button counter
static uint8_t g_u8CountDecs = 0U;           //'-' button counter

uint8_t g_u8ISRDigitSelect = 0U;
uint8_t g_au8Digits[3U] =
{
    SYM_OFF, //unit
    SYM_OFF, //ones
    SYM_OFF  //tens
};

void vInit( void );
void vSetValue( uint8_t u8Value, uint8_t u8Unit );
void vSetDisplayDigits( uint8_t u8Tens, uint8_t u8Ones, uint8_t u8Unit );
void vReadButtons( void );
void vCalculate( void );

/************************************************************************/
/* Timer1 ISR - show values on display                                  */
/************************************************************************/
ISR ( TIMER1_COMPA_vect )
{
    PORTB = 0;
    PORTD = 0;
    _delay_us(2);
    PORTB = SELECT_DIGIT(g_u8ISRDigitSelect);
    PORTD = g_au8Symbols[g_au8Digits[g_u8ISRDigitSelect]];
    g_u8ISRDigitSelect++;
    if (g_u8ISRDigitSelect > 2U)
    {
        g_u8ISRDigitSelect = 0U;
    }
}

/************************************************************************/
/* main()                                                               */
/************************************************************************/
int main(void)
{
    /* Init I/O: */
    vInit();
    
    /* Set default value: */
    vSetDisplayDigits( SYM_DASH, SYM_DASH, SYM_DASH );
        
    /* wait 3 seconds */
    _delay_ms(3000);
    
    /* Set default value: */
    vSetValue( g_u8WaterTemperature, SYM_DEG_CELCIUS );
    
    while ( 1 )
    {
        vReadButtons();
        vCalculate();
        _delay_ms(3);
    }

    return 0;
}

/************************************************************************/
/* Initialize inputs and outputs                                        */
/************************************************************************/
void vInit( void )
{
    /* Port D - Pins 0-7: Outputs */
    DDRD = 0b11111111U;
    
    /* Port B - Pins 0-2: Outputs */
    DDRB = 0b00000111U;
    
    /* Port C - Pins 4-5: Inputs with internal Pull-up */
    PORTC = 0b00110000U;
    
    /* 16-bit TIMER1 in CTC mode
     * prescaler = 8
     * 20 MHz / 8 = 2.5 MHz
     * Compare value = 2500 => 1 ms IRQ
     */
    TCCR1A = 0U;
    TCCR1B = (1<<WGM12) | (1<<CS11);
    OCR1A = 2500U;
    TIMSK1 |= (1<<OCIE1A);
    sei();
    
    return; //void
}

/************************************************************************/
/*                                                                      */
/************************************************************************/
void vDigitTest( void)
{
    PORTB = SELECT_DIGIT(DIGIT_TENS);
    PORTD = 0xFF;
    _delay_ms(1000);
    PORTD = 0;
    _delay_ms(100);
    
        PORTB = SELECT_DIGIT(DIGIT_ONES);
        PORTD = 0xFF;
        _delay_ms(1000);
        PORTD = 0;
        _delay_ms(100);
        
            PORTB = SELECT_DIGIT(DIGIT_UNIT);
            PORTD = 0xFF;
            _delay_ms(1000);
            PORTD = 0;
            _delay_ms(100);
            

    
    return; //void
}

/************************************************************************/
/* Set new values to be shown on display                                */
/************************************************************************/
void vSetValue( uint8_t u8Value, uint8_t u8Unit )
{
    uint8_t u8Tmp = u8Value / 10U;
    vSetDisplayDigits(u8Tmp, u8Value - (u8Tmp * 10U), u8Unit);

    return; //void
}

/************************************************************************/
/* Set display digits individually                                      */
/************************************************************************/
void vSetDisplayDigits( uint8_t u8Tens, uint8_t u8Ones, uint8_t u8Unit )
{
    g_au8Digits[DIGIT_TENS] = u8Tens;
    g_au8Digits[DIGIT_ONES] = u8Ones;
    g_au8Digits[DIGIT_UNIT] = u8Unit;
    
    return; //void
}

/************************************************************************/
/* Read button status                                                   */
/************************************************************************/
void vReadButtons( void )
{
    if ( !(PINC & (1<<PINC4)) ) //if button '+' pressed
    {
        g_u8CountIncs++;
    }
    else
    {
        g_u8CountIncs = 0U; //reset button counter
    }
    if ( !(PINC & (1<<PINC5)) ) //if button '-' pressed
    {
        g_u8CountDecs++;
    }
    else
    {
        g_u8CountDecs = 0U; //reset button counter
    }

    return; //void
}

/************************************************************************/
/*                                                                      */
/************************************************************************/
void vCalculate( void )
{
    bool blChanged = false;
    
    if ( g_u8CountIncs > BUTTON_THRESHOLD )
    {
        g_u8WaterTemperature++;
        if ( g_u8WaterTemperature > TEMP_MAX )
        {
            g_u8WaterTemperature = TEMP_MIN;
        }            
        blChanged = true;
        g_u8CountIncs = 0U; //reset increment counter
    }
    if ( g_u8CountDecs > BUTTON_THRESHOLD )
    {
        if ( g_u8WaterTemperature == TEMP_MIN )
        {
            g_u8WaterTemperature = TEMP_MAX;
        }
        else
        {
            g_u8WaterTemperature--;
        }
        blChanged = true;
        g_u8CountDecs = 0U; //reset decrement counter
    }

    if ( blChanged )
    {
        vSetValue( g_u8WaterTemperature, SYM_DEG_CELCIUS );
    }    

    return; //void
}