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;;

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;; Driving 7-segment LED displays over SPI

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;;

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; Output Enable control

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.equ LED7_DDR    = DDRB

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.equ LED7_PORT   = PORTB

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.equ LED7_OE     = PORTB1                ; Output Enable (Low)

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    10

; Font for 7-segment display

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; Includes decimal digits 0-9, hexadecimal digits A-F, and some special chars

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LED7_Font:

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.db     0b00111111, 0b00000110      ; 0, 1

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.db     0b01011011, 0b01001111      ; 2, 3

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.db     0b01100110, 0b01101101      ; 4, 5

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.db     0b01111101, 0b00000111      ; 6, 7

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.db     0b01111111, 0b01100111      ; 8, 9

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.db     0b01110111, 0b01111100      ; A, b

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.db     0b00111001, 0b01011110      ; C, d

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.db     0b01111001, 0b01110001      ; E, f

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.db     0b10000000, 0b00000000      ; ., 

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.equ LED7_0     = 0

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.equ LED7_1     = 1

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.equ LED7_2     = 2

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.equ LED7_3     = 3

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.equ LED7_4     = 4

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.equ LED7_5     = 5

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.equ LED7_6     = 6

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.equ LED7_7     = 7

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.equ LED7_8     = 8

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.equ LED7_9     = 9

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.equ LED7_A     = 10

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.equ LED7_B     = 11

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.equ LED7_C     = 12

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.equ LED7_D     = 13

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.equ LED7_E     = 14

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.equ LED7_F     = 15

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.equ LED7_DOT   = 16

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.equ LED7_EMPTY = 17

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    42

; LEDs are on beginning of SPI universe

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.set led7_buffer = spi_outbuf + 0

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    45

;; Initialize LCD to empty, and enable

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LED7_Init:

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    ; Setup ENable port

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        sbi         LED7_PORT, LED7_OE    ; Disabled (Low)

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        sbi         LED7_DDR, LED7_OE     ; Out

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    51

    ; Initialize buffer

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        ldi         r16, 0b01000000

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        sts         led7_buffer + 0, r16

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        sts         led7_buffer + 1, r16

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    56

    ; Update display

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        rcall       SPI_SendRecv

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    59

    ; Enable output once the initial display has been shifted out

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        cbi         LED7_PORT, LED7_OE

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    62

    ; Done

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        ret

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    65

LED7_LoadChar:

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        clr         r0, 0

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    68

    ; Prep address

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        ; base addr for font table

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        ldi         ZH, high(2 * LED7_Font)

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        ldi         ZL, low(2 * LED7_Font)

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        ; offset

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        add         ZL, r8

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        adc         ZH, r0

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    77

    ; Load char

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        lpm         r8, Z

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    80

    ; Done

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        ret

    82

    83

;; Display an 8-bit hexadecimal value on the display

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;;  Input: r16

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LED7_ShowHex:

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        ; base16

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        ldi         r17, 16 

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    89

        ; 1's

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        call        div8u

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    92

        ; r16 = result, r15 = remainder

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        mov         r17, r15 

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    95

    ; Continue

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        rjmp        LED7_Show

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    98

;; Display an 8-bit decimal value on the display

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;;  Input: r16

   100

LED7_ShowDec:

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        ; base10

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        ldi         r17, 10

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   104

        ; 1's

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        call        div8u

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        mov         r8, r15

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   108

        ; 10's

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        call        div8u

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        mov         r9, r16         ; 100's

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   112

        ; 1's from r8

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        rcall       LED7_LoadChar

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        mov         r17, r8

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   116

        ; 10's from r15

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        mov         r8, r15

   118

        rcall       LED7_LoadChar

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        mov         r16, r8

   120

   121

        ; Set dots for 100's 

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        sbrc        r9, 0

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        ori         r17, 0b10000000 ; +100

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        sbrc        r9, 1

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        ori         r16, 0b10000000 ; +200

   126

   127

    ; Continue

   128

        rjmp        LED7_ShowRaw

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   130

;; Display a single digit on the display

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;;  Input: r16, r17

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LED7_Show:

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        mov         r8, r16

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        rcall       LED7_LoadChar

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        mov         r16, r8

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   137

        mov         r8, r17

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        rcall       LED7_LoadChar

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        mov         r17, r8

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   141

    ;; Continue

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   143

;; Display a raw segment mask

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;;  Input: r16, r17

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LED7_ShowRaw:

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    ; Store buffer

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        sts         led7_buffer + 0, r16

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        sts         led7_buffer + 1, r17

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    ; Update display

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        rjmp        SPI_Update

   152