140 lines
2.5 KiB
NASM
140 lines
2.5 KiB
NASM
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; lcd
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;
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; Implement PutC on TI-84+ (for now)'s LCD screen.
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;
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; *** Requirements ***
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; fnt/mgm
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;
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; *** Constants ***
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.equ LCD_PORT_CMD 0x10
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.equ LCD_PORT_DATA 0x11
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.equ LCD_CMD_6BIT 0x00
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.equ LCD_CMD_DISABLE 0x02
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.equ LCD_CMD_ENABLE 0x03
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.equ LCD_CMD_XINC 0x05
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.equ LCD_CMD_YINC 0x07
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.equ LCD_CMD_COL 0x20
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.equ LCD_CMD_ROW 0x80
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.equ LCD_CMD_CONTRAST 0xc0
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; *** Code ***
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lcdInit:
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; Enable the LCD
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ld a, LCD_CMD_ENABLE
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call lcdWait
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out (LCD_PORT_CMD), a
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; Hack to get LCD to work. According to WikiTI, we're to sure why TIOS
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; sends these, but it sends it, and it is required to make the LCD
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; work. So...
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ld a, 0x17
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call lcdWait
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out (LCD_PORT_CMD), a
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ld a, 0x0b
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call lcdWait
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out (LCD_PORT_CMD), a
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; Set some usable contrast
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ld a, LCD_CMD_CONTRAST+0x34
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call lcdWait
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out (LCD_PORT_CMD), a
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; Enable 6-bit mode.
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ld a, LCD_CMD_6BIT
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call lcdWait
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out (LCD_PORT_CMD), a
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; Enable X-increment mode
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ld a, LCD_CMD_XINC
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call lcdWait
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out (LCD_PORT_CMD), a
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ret
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; Wait until the lcd is ready to receive a command
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lcdWait:
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push af
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.loop:
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in a, (LCD_PORT_CMD)
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; When 7th bit is cleared, we can send a new command
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rla
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jr c, .loop
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pop af
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ret
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; Turn LCD off
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lcdOff:
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ld a, LCD_CMD_DISABLE
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call lcdWait
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out (LCD_PORT_CMD), a
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ret
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; Set LCD's current column to A
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lcdSetCol:
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; The col index specified in A is compounded with LCD_CMD_COL
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add a, LCD_CMD_COL
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call lcdWait
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out (LCD_PORT_CMD), a
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ret
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; Set LCD's current row to A
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lcdSetRow:
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; The col index specified in A is compounded with LCD_CMD_COL
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add a, LCD_CMD_ROW
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call lcdWait
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out (LCD_PORT_CMD), a
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ret
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; Send the 5x7 glyph that HL points to to the LCD, at its current position.
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; After having called this, the LCD's position will have advanced by one
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; position
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lcdSendGlyph:
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push af
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push bc
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push hl
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; For the purpose of this program, we only write on the first line.
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; We can assume that we always start at row 0.
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xor a
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call lcdSetRow
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ld b, 7
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.loop:
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ld a, (hl)
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inc hl
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call lcdWait
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out (LCD_PORT_DATA), a
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djnz .loop
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; Now that we've sent our 7 rows of pixels, let's go in "Y-increment"
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; mode to let the LCD increase by one column after we've sent our 8th
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; line, which is blank (padding).
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ld a, LCD_CMD_YINC
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call lcdWait
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out (LCD_PORT_CMD), a
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; send blank line
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xor a
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call lcdWait
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out (LCD_PORT_DATA), a
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; go back in X-increment mode
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ld a, LCD_CMD_XINC
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call lcdWait
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out (LCD_PORT_CMD), a
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pop hl
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pop bc
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pop af
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ret
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lcdPutC:
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push hl
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call fntGet
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jr nz, .end
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call lcdSendGlyph
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.end:
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pop hl
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ret
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