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First working text mode without end of screen scroll

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Daniele Verducci su MatissePenguin
2021-01-26 23:22:55 +01:00
parent 9d6e6efd13
commit 467197fd23
2 changed files with 103 additions and 12 deletions
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61
pat80-io-devices/composite-pal-adapter/software/avr-assembly/character_generator.asm
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@@ -27,7 +27,7 @@ draw_char:
; Obtain offset multiplying ascii_code * number_of_bytes_per_font
ldi r17, FONT_HEIGHT
mul HIGH_ACCUM, r17 ; result overwrites r0 and r1!
; 16-bit addition between gliph's first byte position and offset (and store result in Z)
; 16-bit addition between gliph's first byte position and offset (and store result in Z) to obtain our glyph position
add ZL, r0
adc ZH, r1
; Z contain our glyph's first byte position: draw it
@@ -44,19 +44,66 @@ draw_char:
; Decrement loop counter and exit if reached 0
dec HIGH_ACCUM
brne draw_char_loop
; Char drawing is complete. Set chunk cursor position to next char first line
; Char drawing is complete. Increment cursor position
inc POS_COLUMN
; Check if end of line
cpi POS_COLUMN, 52
breq draw_char_eol
; Reset chunk position to first glyph line of next column
mov YL, r2 ; first restore Y
mov YH, r3
adiw YH:YL,1 ; just increment pre-char-drawing-saved chunk cursor position by 1
ret
draw_char_eol:
clr POS_COLUMN ; reset column to 0
adiw YH:YL,1 ; increment chunk cursor position by 1 (begin of next line on screen)
; Check if end of screen
cpi YH, high(FRAMEBUFFER_END + 1)
brne draw_char_end
cpi YL, low(FRAMEBUFFER_END + 1)
brne draw_char_end
; End of screen reached! Scroll framebuffer by 1 line (=52*FONT_HEIGHT bytes)
; TODO
draw_char_end:
ret
; Sets the cursor to 0,0 and clears fine position
cursor_pos_home:
; Set Y to framebuffer start
;ldi YH, high(FRAMEBUFFER)
;ldi YL, low(FRAMEBUFFER)
ldi YH, high(0x0068)
ldi YL, low(0x0068)
; Set all positions to 0
clr POS_COLUMN
clr POS_ROWP
clr POS_FINE
; Load framebuffer start position to Y
ldi YH, high(FRAMEBUFFER)
ldi YL, low(FRAMEBUFFER)
; ldi YH, high(0x1000)
; ldi YL, low(0x1000)
ret
; Updates framebuffer pointer (Y) to point to current text cursor position (POS_COLUMN, POS_ROWP)
; Usage:
; ldi POS_COLUMN, 55
; ldi POS_ROWP, 13
; call set_framebuffer_pointer_to_text_cursor ; (sets cursor to 4th character of second row in 13th row-pair = column 4, row 27 on screen)
; @modifies Y, R0, R1
set_framebuffer_pointer_to_text_cursor:
; Load framebuffer start position to Y
ldi YH, high(FRAMEBUFFER)
ldi YL, low(FRAMEBUFFER)
; Obtain offset between 0,0 and current cursor position
mul POS_COLUMN, POS_ROWP ; result is in r1,r0
; Sum offset to Y
add YL, r0
adc YH, r1
ret
; Draws a newline
; Moves cursor to start of following screen line
; Takes care of particular cases, i.e. end of screen (shifts all screen up by one line)
draw_carriage_return:
ret