1 ;; Basic LED matrix fonts

     2 ;; vim: set ft=avr:

     3 

     4 .cseg

     5 

     6 ;; Font definition

     7 ; Defines FONT_8x6 symbol

     8 .include "font.def"

     9 

    10 ; Font to use

    11 .set FONT_TABLE     = FONT_8x6

    12 .set FONT_START     = FONT_8x6_START

    13 .set FONT_END       = FONT_8x6_END

    14 .set FONT_COLS      = FONT_8x6_COLS

    15 .set FONT_ROWS      = FONT_8x6_ROWS     ; XXX: fixed to 8

    16 

    17 ;; Render the given ASCII char into the given buffer

    18 ; Input:    r16 - ASCII char code

    19 ;           Y   - dest buf (Wx8 column data)

    20 Font_Render:

    21     ; Test char index

    22 

    23         ; test under-range

    24         ldi     r17, FONT_START

    25         cp      r16, r17

    26         brlt    f_render_invalid

    27 

    28         ; test over-range

    29         ldi     r17, FONT_END

    30         cp      r17, r16

    31         brlt    f_render_invalid

    32 

    33     ; Locate font char

    34         ; compute offset in chars (r16)

    35         subi    r16, FONT_START

    36 

    37         ; compute offset in bytes (r1:r0)

    38         ldi     r17, FONT_COLS

    39         mul     r16, r17

    40 

    41         ; font table start offset from words

    42         ldi     ZL, low(FONT_TABLE * 2)

    43         ldi     ZH, high(FONT_TABLE * 2)

    44 

    45         ; apply offset

    46         add     ZL, r0

    47         adc     ZH, r1

    48 

    49     ; Copy column pixel data

    50         ; count columns

    51         ldi     r16, FONT_COLS

    52 f_render_cpy:

    53         

    54         ; copy via r17

    55         lpm     r17, Z+

    56         st      Y+, r17

    57 

    58         dec     r16

    59         brne    f_render_cpy

    60 

    61 f_render_invalid:

    62 

    63     ; Done

    64         ret

    65