55 lines
1.3 KiB
NASM
55 lines
1.3 KiB
NASM
; HD44780 20x4 characters LCD display driver
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; @author Daniele Verducci
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; variables
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;lcd_cur_x: EQU DRV_VAR_SPACE
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;lcd_cur_y: lcd_cur_x + 1
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; functions
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lcd_init:
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;reset procedure
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ld a,0x38
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out (LCD_INSTR_REG),a
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ld a,0x08
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out (LCD_INSTR_REG),a
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ld a,0x01
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out (LCD_INSTR_REG),a
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;init procedure
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ld a,0x38
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out (LCD_INSTR_REG),a
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ld a,0x0F
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out (LCD_INSTR_REG),a
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ret
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; Writes text starting from current cursor position
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; @param BC Pointer to a null-terminated string first character
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lcd_print:
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ld a, (bc) ; bc is the pointer to passed string's first char
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cp 0 ; compare A content with 0 (subtract 0 from value and set zero flag Z if result is 0)
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ret z ; if prev compare is true (Z flag set), string is finished, return
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out (LCD_DATA_REG),a ; output char
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inc bc ; increment bc to move to next char
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jp lcd_print
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; Set cursor position
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; @param B X-axis position (0 to 19)
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; @param C Y-axis position (0 to 3)
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lcd_locate:
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ld a,0xFE
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out (LCD_INSTR_REG),a ; warns the lcd microcontroller that a command is coming
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ld a,0xA8
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out (LCD_INSTR_REG),a ; place cursor to first char of second line
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ret
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; Clears the screen
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lcd_cls:
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ld a,0x01
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out (LCD_INSTR_REG),a ; clear display
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ld a,0x02
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out (LCD_INSTR_REG),a ; cursor to home (top left)
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ret
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