.include "m2560def.inc"

.def temp = r16
.def counterP0 = r17
.def counterP1 = r18
.def leds = r19
.def displayCount = r20
.equ displayLength = 6
.equ false = 0
.equ true = 1


.macro twoByteClear
    ldi YL, low(@0)
    ldi YH, high (@0)
    clr temp
    st Y+, temp
    st Y, temp
.endmacro

.dseg
pattern0:       .byte 1
pattern1:       .byte 1
tempcounter:    .byte 2
Timer1Counter:  .byte 1
Timer3Counter:  .byte 1
PB0Status:      .byte 1
PB1Status:      .byte 1


.cseg
.org 0x0000
    jmp RESET
.org INT0addr
    jmp PB0Press
.org INT1addr
    jmp PB1Press
    jmp DEFAULT
.org OVF1addr
    jmp TIMER1OVF
    jmp DEFAULT
.org OVF0addr
    jmp TIMER0OVF
.org OVF3addr
    jmp TIMER3OVF


DEFAULT:
    reti


RESET:
    ldi temp, high(RAMEND)
    out sph, temp
    ldi temp, low(ramend)
    out spl, temp

    clr temp
    out ddrd, temp                  //first two pins of port d ( RDx3 and RDx4 on the board) are mapped to input buttons; set port d as input
    ser temp
    out ddrc,temp                   //set port c as output

    clr temp
    sts PB0Status, temp
    sts PB1Status, temp

    clr temp
    clr leds
    clr counterP0
    clr counterP1
    clr displayCount

    sts pattern0, temp
    sts pattern1, temp

    rjmp main

PB0Press:
    push temp
    in temp, sreg
    push temp               //pushing sreg
    push YL
    push YH

    lds temp, PB0Status
    cpi temp, 1
    breq PB0Press_end

    ldi temp,1
    sts PB0Status, temp

    cpi counterP0, 8        //check if pattern0 is full yet
    breq PB0Press_end           //if it is, check pattern1
    lds temp, pattern0      //otherwise, load pattern0
    lsl temp                //left shift pattern to store most recent entry (0) as LSB
    sts pattern0, temp
    inc counterP0

    PB0Press_end:
    pop YH
    pop YL
    pop temp                //popping sreg
    out sreg, temp
    pop temp
    reti

PB1Press:
    push temp
    in temp, sreg
    push temp               //pushing sreg
    push YL
    push YH

    lds temp, PB1Status
    cpi temp, 1
    breq PB1Press_end

    ldi temp,1
    sts PB1Status, temp

    cpi counterP0, 8        //check if pattern0 is full yet
    breq PB1Press_end       //if it is, check pattern1
    lds temp, pattern0      //otherwise, load pattern0
    lsl temp                //left shift pattern to store most recent entry (0) as LSB
    inc temp
    sts pattern0, temp
    inc counterP0

    PB1Press_end:
    pop YH
    pop YL
    pop temp                //popping sreg
    out sreg, temp
    pop temp
    reti

Timer0OVF:
    in temp, sreg
    push temp
    push yh
    push yl
    push XH
    push XL

    cpi leds, 0x00                  //check if the leds are empty
    brne doNothing                  //if they are not, do nothing

    cpi counterP0, 8                //check if the pattern0 is full
    brne doNothing
    lds leds, pattern0              //if it is full, load it to leds
    clr counterP0                   //clear counter P0, so it is ready for new input

    doNothing:

    lds XL,tempcounter
    lds XH,tempcounter+1
    adiw X,1

    cpi XL, low(7812)
    ldi temp, high(7812)
    cpc XH, temp
    brne notASecond

    next:
    cpi leds, 0x00                      //check there is a value loaded in the leds
    breq noDisplay                      //if there isnt, then nothing will be displayed, keep counting
    cpi displayCount, displayLength         //check if there have been previous displays
    brge alreadyDisplayed               //if there is, clear display and continue to nodisplay
    mov temp, displayCount                  //copy over to temp
    andi temp, 0b00000001               //mask display to just the LSB
    cpi temp, 0                         //check if the LSB is 0. if it is, number is even -> turn on
    breq display                        //if it is , go to display to turn on leds
    clr temp                            //otherwise, if the number is odd
    out PORTC,temp                      //turn off leds
    inc displayCount                    //incrments counter
    rjmp NoDisplay

    display:
    out PORTC, leds                     //turn on leds
    inc displayCount                    //increment displayCOunt
    rjmp noDisplay                      //proceed to clear tempcounter

    alreadyDisplayed:
    clr displayCount
    clr leds

    rjmp noDisplay

    noDisplay:

    twoByteClear tempcounter
    rjmp epilogue

    notASecond:
    sts tempcounter, XL
    sts tempcounter+1,XH

    epilogue:
    pop XL
    pop XH
    pop YL
    pop YH
    pop temp
    out sreg,temp
    reti

TIMER1OVF:                  //this timer will overfloew every ~30ms with a prescalar of 8 for 16-bit timer
    push temp               //
    in temp, sreg
    push temp
    push yh
    push yl

    lds temp, PB0Status
    cpi temp, 1
    breq new501

    new501:
        lds YL, Timer1Counter
        ldi YH, 0
        adiw Y,1
        cpi YL, low(25)
        ldi temp, high(25)
        cpc temp, YH
        brne NOt501

        clr temp
        sts PB0Status, temp
        sts Timer1Counter, temp
        clr YL
        clr YH
        rjmp timer1end

    NOt501:
        sts Timer1Counter, YL

    timer1end:
    pop YL
    pop YH
    pop temp
    out sreg, temp
    pop temp
    reti

TIMER3OVF:                  //this timer will overfloew every ~30ms with a prescalar of 8 for 16-bit timer
    push temp               //
    in temp, sreg
    push temp
    push yh
    push yl

    lds temp, PB1Status
    cpi temp, 1
    breq new503

    new503:
        lds YL, Timer3Counter
        ldi YH, 0
        adiw Y,1
        cpi YL, low(25)
        ldi temp, high(25)
        cpc temp, YH
        brne NOt503

        clr temp
        sts PB1Status, temp
        sts Timer3Counter, temp
        clr YL
        clr YH
        rjmp timer3end

    NOt503:
        sts Timer3Counter, YL

    timer3end:
    pop YL
    pop YH
    pop temp
    out sreg, temp
    pop temp
    reti

main:
    twoByteClear tempCounter

    ldi temp, 0b00000000
    out tccr0a,temp
    ldi temp,0b00000010
    out tccr0b, temp
    ldi temp, 1<< toie0
    sts timsk0,temp

    ldi temp, 0b00000011
    out eimsk, temp             //external interrupt mask register, 2 LSB are for int0 and int1. enabling this and global interrupts enables the interrupt pin
    ldi temp, 0b00001010
    sts eicra,temp              //enable falling edge, with ISCn1 = 1, ISCn0 = 0, for falling edge of INTn. eicra is for INT3:0. using sts as its a register

    ldi temp, 0b00000000    //counter in normal mode (UP), rolls over at
    sts TCCR1A, temp        //maximum 16 bit value and restarts from bottom
    ldi temp, 0b00000010    //overflow at 2^16 * 8/16 = 32768microseconds, with 8 prescalar
    sts TCCR1B, temp
    ldi temp, 1<<TOIE1      //enable timer1
    sts timsk1, temp

    ldi temp, 0b00000000    //counter in normal mode (UP), rolls over at
    sts TCCR3A, temp        //maximum 16 bit value and restarts from bottom
    ldi temp, 0b00000010    //overflow at 2^16 * 8/16 = 32768microseconds, with 8 prescalar
    sts TCCR3B, temp
    ldi temp, 1<<TOIE3      //enable timer1
    sts timsk3, temp

    ldi temp, true
    sts PB0Status, temp
    sei

end:
    rjmp end