/* Write a subrotine to convert a BCD number into an 8-bit value
 * ready to be sent to the 7-segment display on the CSULB protoshield. 
 * Source:
 * 1. AVR Addressing Indirect
 *    http://www.csulb.edu/~hill/ee346/Lectures/13%20AVR%20Addressing%20Indirect.pdf
 */
.INCLUDE <m328pdef.inc>

.DSEG
A:     .BYTE 1

.CSEG

.ORG 0x0000

RST_VECT:
 rjmp setup

.ORG 0x0100 ; bypass IVT
.INCLUDE "spi_shield.inc" 

setup:
    rcall initShield
	clr    spiLEDS   	// turn off discrete red LEDs
loop:
    lds    r24, A
    rcall  BCD_to_7SEG
    mov    spi7SEG, r24
    call   WriteDisplay	
rjmp loop

; --------------------------
; ------ BCD to 7SEG -------
; Called from Home subroutine
; Inputs: r24    Output: r24
; The input is a 4-bit binary number and the output are the segments
; to turn on to view display this number on a 7-segment display.
; SREG and register r1 are modified by this subroutine  
; --------------------------

BCD_to_7SEG:
	cbr     r24,0b11110000      ; limit to 1 nibble
    ldi     ZL,low(table<<1)    ; load address of look-up table
    ldi     ZH,high(table<<1)
    clr     r1
    add     ZL, r24
    adc     ZH, r1
    lpm     r24, Z
	ret

//                   0           1           2           3
//             gfedcba     gfedcba     gfedcba     gfedcba     gfedcba     gfedcba
table: .DB  0b00111111, 0b00000110, 0b01011011, 0b01001111, 0b01100110, 0b01101101
//          0           1           2           3           4           5
       .DB  0b01111101, 0b00000111, 0b01111111, 0b01100111, 0b01110111, 0b01111100
//          6           7           8           9           A           B     
	   .DB  0b00111001, 0b01011110, 0b01111001, 0b01110001
//          C           D           E           F