;   Write an assembly code that repeatedly cycles RGB LED
; from red to green to blue (holding each color for 0.5 seconds)
; in main code. Use the timer functionality to cycle one motor
; at a time through the following steps (0.3 seconds per step):

;   1. Right motor forward at 100% power
;   2. Reduce power to 50%
;   3. Left motor backward at 100% power
;   4. Reduce power to 50%
;   5. Left motor forward at 100% power
;   6. Reduce power to 50%
;   7. Right motor backward at 100% power
;   8. Reduce power to 50%
;   9. Go to step 1


    list p=18F1220
    radix hex
    config WDT=OFF,LVP=OFF,OSC=INTIO2

#include p18F1220.inc

#define dCount 0x80
#define dCountInner 0x81
#define WregShadow 0x82

#define CurrentStateMotor 0x83
#define CurrentStateLED 0x84

    ; There are a few states we could be in
    ; 0 Right motor -	forward	    100%
    ; 1 Right motor -	forward	    50%

    ; 2 Left motor  -	backward    100%
    ; 3 Left motor  -	backward    50%

    ; 4 Left motor  -	forward	    100%
    ; 5 Left motor  -	forward	    50%

    ; 6 Right motor -	backward    100%
    ; 7 Right motor -	backward    50%

    org 0x00
    GOTO Init

    org 0x08 ; HTimer 0 interrupt (for RGB LED cycling)
    GOTO RGBCycle

    org 0x18	; Timer 1 interrupt (for motor cycling)
    GOTO MotorCycle

    org 0x20
Init:
    ; Setting up EDbot
    CLRF PORTA
    CLRF PORTB
    MOVLW 0x7F
    MOVWF ADCON1
    MOVLW 0x35
    MOVWF TRISA
    MOVLW 0xC3
    MOVWF TRISB

    ; Set the internal system clock to 4 MHz
    ; This means that each instruction cycle will take 1 microsecond
    MOVLW 0x70
    IORWF OSCCON

    ; Setting up timer
    BSF INTCON, PEIE	    ; enable peripheral interrupts
    BSF INTCON, TMR0IE	    ; enable TMR0 interrupt
    BSF INTCON2, TMR0IP	    ; set TMR0 to high priority
    BSF RCON, IPEN	    ; priority levels enabled
    BCF INTCON, TMR0IF	    ; clear TMR0 flag so it can fire

    BSF PIE1, TMR1IE	    ; enable TMR1 interrupt
    BCF IPR1, TMR1IP	    ; set TMR1 to low priority
    BCF PIR1, TMR1IF	    ; clear TMR1 flag so it can fire

    ; Timer 0 should be firing every 0.5 seconds

    ; Setting data for T0CON
    ; 0100 0001
    ; Bit	Meaning	    Value
    ; ==============================================
    ; 7		TMR0ON	    0	(off - we don't want it firing yet)
    ; 6		T08BIT	    0	(16-bit mode)
    ; 5		T0CS	    0	(internal clock)
    ; 4		T0SE	    0	(rising edge)

    ; 3		PSA	    0	(prescaler assigned)
    ; 2		T0PS2	    0
    ; 1		T0PS1	    1
    ; 0		T0PS0	    0	(1:8 prescale value)

    MOVLW 0x02
    MOVWF T0CON		    ; 1 timer tick takes 8 microseconds
			    ; thus, it will take 8 * 65536 = 524288 microsecs
			    ; = approx 0.52 seconds to interrupt (close enough)

			    ; 8x = 500000
			    ;  x =  62500
			    ; 65536 - 62500 = 3036 (0x0BDC)

    MOVLW 0x0B
    MOVWF TMR0H
    MOVLW 0xDC
    MOVWF TMR0L

    CLRF TMR0H
    CLRF TMR0L



    ; Timer 1 should fire every 0.3 seconds
    ; Setting data for T1CON
    ; 1111 1000
    ; Bit	Meaning	    Value
    ; ==============================================
    ; 7		RD16	    1	(16-bit read mode)
    ; 6		T1RUN	    1	(Use TMR1 oscillator)
    ; 5		T1CKPS1	    1
    ; 4		T1CKPS0	    1	(1:8 Prescale amount)

    ; 3		T1OSCEN	    1	(TMR1 oscillator enabled)
    ; 2		T1SYNC	    0	(Useless)
    ; 1		TMR1CS	    0	(Internal clock)
    ; 0		TMR1ON	    0	(Not enabled for now)

    MOVLW 0xF8
    MOVWF T1CON

    ; 1 timer tick takes 8 microseconds
    ; thus, it will take 8 * 65536 = 524288 microsecs
    ; = approx 0.52 seconds to interrupt
    ; this is NOT GOOD
    ; we want it to take 0.3 secs = 300000 microsecs
    ; 8x = 300000
    ; x  =  37500


    ; 65536 - 37500 = 28036 (0x6D84)

    MOVLW 0x6D
    MOVWF TMR1H
    MOVLW 0x84
    MOVWF TMR1L


    BSF T1CON, TMR1ON	    ; enable TMR1
    BSF T0CON, TMR0ON	    ; enable TMR0
    BSF INTCON, GIE	    ; enable interrupts globally

Loop:
    BRA Loop


RGBCycle:
    BTG PORTB, 2 ; toggle Red LED

    MOVLW 0x0B
    MOVWF TMR0H
    MOVLW 0xCD
    MOVWF TMR0L
    BCF INTCON, TMR0IF
    RETFIE

MotorCycle:
    ;BTG PORTA, 3 ; toggle Green LED

    ; CurrentState
    INCF CurrentStateMotor

    ; Let's make sure we're not at a state > 8
    MOVLW .8
    SUBWF CurrentStateMotor
    BZ ResetMotorCycle

FinishMotorCycle:
    MOVLW 0x6D
    MOVWF TMR1H
    MOVLW 0x84
    MOVWF TMR1L
    BCF PIR1, TMR1IF
    RETFIE

ResetMotorCycle:
    CLRF CurrentStateMotor
    BRA FinishMotorCycle

    END