;***************************************************************************
;
; File Name		:'lcd4.asm"
; Title			:HD44xx kompatibilis LCD Driver (I/O Port)
; Date			:2003.10.28.
; Version		:1.0.0
; Support telephone	:+36-70-333-4034,  old: +36-30-9541-658 VFX
; Support fax		:
; Support Email		:info@vfx.hu
; Target MCU		:ATmega128
;
;***************************************************************************
;	D E S C R I P T I O N
;
; http://home.iae.nl/users/pouweha/lcd/lcd.shtml
;
; Support 2x16 char LCD
;
;***************************************************************************
;	M O D I F I C A T I O N   H I S T O R Y
;
;
;       rev.      date      who  	why
;	----	----------  ---		------------------------------------
;	0.01	2003.10.28  VFX		Creation
;
;***************************************************************************
;Hardware
;***************************************************************************
;*
;*	SYSCLK: f=16.000 MHz (T= 62.5 ns)
;*
;***************************************************************************
;
;
;**************************************************************************
;* Hardware Def.
;
;***************************************************************************


.equ	LCDRS_PORT=PORTD	;LCD Register Select
.equ	LCDRS_DIR=DDRD		;Register Select 1=data 0=command
.equ	LCDRS=0

.equ	LCDRW_PORT=PORTD	;LCD Read/Write
.equ	LCDRW_DIR=DDRD		;0=write to display, 1= read from display
.equ	LCDRW=1

.equ	LCDEN_PORT=PORTD	;LCD Enable
.equ	LCDEN_DIR=DDRD		;Enable - data clocked on falling edge
.equ	LCDEN=4

.equ	LCDDAT_PORT=PORTF	;LCD Data PortF[3..0]
.equ	LCDDAT_DIR=DDRF
.equ	LCDDAT_PIN=PINF
.equ	LCDDAT_Mask=0b00001111




;***************************************************************************
;**** VARIABLES
.DSEG



;***************************************************************************
.ESEG


;***************************************************************************
;**** CODE SEG
;***************************************************************************
.CSEG


;*****************************************************
;** Wait1ms
;**
;**  In: R16 - 16*1ms varakozas
;**
;**  Out: -
;**
;**
;** Alt R16
;**
;** Description:  wating for R16 * 1 ms
;*
Wait1ms:
		ldi	XL,low(SYSCLK/(5*1000))
		ldi	XH,high(SYSCLK/(5*1000))
Waitx1:		sbiw	XL,1		;[2] \
		nop			;[1]  - 5 cycles in loop
		brne	Waitx1		;[2] /
		dec	R16
		brne	Wait1ms
		ret




;*****************************************************
;** LCD_pulseE
;**
;**  In: - 
;**
;**  Out: R0 - Data on LCDDat pin
;**
;**
;** Alt 
;**
;** Description:  Generate ENABLE signal to LCD
;*
LCD_pulseE:
		sbi	LCDEN_PORT,LCDEN	;Enable high
		nop				;Wait 500ns @16MHz
		nop
		nop
		nop
		nop
		nop
		nop
		nop
		in	R0,LCDDAT_PIN
		cbi	LCDEN_PORT,LCDEN	;Enable low, latch data
		ret



;*****************************************************
;** LCD_Init
;**
;**  In: -
;**
;**  Out: -
;**
;**
;** Alt: 
;**
;** Description:  Initialize LCD in 4 bit mode
;*
LCD_Init:
		sbi	LCDEN_DIR,LCDEN		;LCD I/O Disabled
		cbi	LCDEN_PORT,LCDEN


		sbi	LCDRS_DIR,LCDRS		;Sel. LCD Command Register
		cbi	LCDRS_PORT,LCDRS

		sbi	LCDRW_DIR,LCDRW		;LCD Write mode
		cbi	LCDRW_PORT,LCDRW

		ldi	R16,LCDDAT_Mask		;LCD Data lines outputs
		sts	LCDDAT_DIR,R16
		ldi	R16,0			;All zeros
		sts	LCDDAT_PORT,R16

		ldi	R16,15			;Wait at least 15msec after
		rcall	Wait1ms			;powerup before writing to display
						;tuti ami tuti legyen 250ms

		
		; Put the LCD in 8-bit mode.  Even though we want the display to
		; operate in 4-bit mode, the only way to guarantee that our commands
		; are aligned properly is to initialize in 8-bit.  (The user might have
		; hit reset between nibbles of a dual 4-bit cycle.)

		lds	R16,LCDDAT_PORT
		andi	R16,255-LCDDAT_PORT
		ori	R16,0b00000011		;3x probalkozunk 8 bit mode-ba rakni
		sts	LCDDAT_PORT,R16
		nop
		nop
		cbi	LCDRS_PORT,LCDRS	;Set to Command Reg.
		cbi	LCDRW_PORT,LCDRW	;read
		rcall	LCD_pulseE		;1
		ldi	R16,15
		rcall	Wait1ms			;wait 5ms

		cbi	LCDRS_PORT,LCDRS	;Set to Command Reg.
		cbi	LCDRW_PORT,LCDRW	;read
		rcall	LCD_pulseE		;2
		ldi	R16,5
		rcall	Wait1ms			;wait 5ms

		cbi	LCDRS_PORT,LCDRS	;Set to Command Reg.
		cbi	LCDRW_PORT,LCDRW	;read
		rcall	LCD_pulseE		;3
		ldi	R16,5
		rcall	Wait1ms			;wait 5ms
		
		; Now it's safe to go into 4-bit mode.

		lds	R16,LCDDAT_PORT
		andi	R16,255-LCDDAT_PORT
		ori	R16,0b00000010		;4bit bus mode
		sts	LCDDAT_PORT,R16
		rcall	LCD_pulseE
		ldi	R16,5
		rcall	Wait1ms			;wait 5ms


		; *** Send the 'FUNCTION SET' command
		;                +------ Data:  0 = 4-bit; 1 = 8-bit
		;                |+----- Lines: 0 = 1; 1 = 2
		;   	         ||+---- Font:  0 = 5x8; 1 = 5x11
		ldi	R16,0b00101000
		rcall	LCD_SendCmd
	
		; *** Send the 'CURSOR/DISPLAY SHIFT' command
		;                 +----- S/C:  0 = cursor; 1 = display
		;    	          |+---- R/L:  0 = left; 1 = right
		ldi	R16,0b00010100
		rcall	LCD_SendCmd

		; *** Send the 'ENTRY MODE' command
		;      		    +--- Direction: 0 = left; 1 = right
		;  	            |+-- Shift Dislay: 0 = off; 1 = on
		ldi	R16,0b00000110
		rcall	LCD_SendCmd

		; *** Send the 'DISPLAY ON/OFF' command
		;     		   +---- Display: 0 = off; 1 = on
		;     		   |+--- Cursor: 0 = off; 1 = on
		;     		   ||+-- Blink: 0 = off; 1 = on
		ldi	R16,0b00001100
		rcall	LCD_SendCmd

		rcall	LCD_Clear
		ret


;*****************************************************
;** LCD_Clear
;**
;**  In: -
;**
;**  Out: -
;**
;**
;** Alt: 
;**
;** Description:
;** Clears the display and sends the cursor home.
;
LCD_Clear:
		ldi	R16,0b00000001		;Clear LCD
		rcall	LCD_SendCmd
		ldi	R16,0b00000010		;Send the cursor home
		rcall	LCD_SendCmd
		ret

;*****************************************************
;** LCD_WaitBusy
;**
;**  In: -
;**
;**  Out: -
;**
;**
;** Alt: R0, R16
;**
;** Description:
;** Waits for the busy flag to go low.  Since we're in 4-bit mode,
;** the register has to be read twice (for a total of 8 bits).
;*
LCD_WaitBusy:
		push	R16

		lds	R16,LCDDAT_DIR
		andi	R16,255-LCDDAT_Mask	;LCD data bits going to input
		sts	LCDDAT_DIR,R16

		lds	R16,LCDDAT_PORT
		ori	R16,LCDDAT_Mask		;pull-up
		sts	LCDDAT_PORT,R16
		rjmp	LCDWait1

LCDWait0:
		ldi	R16,2			;Wait min. ~1us
LCDWait01:	nop
		dec	R16
		brne	LCDWait01
LCDWait1:
		cbi	LCDRS_PORT,LCDRS	;Set to Command Reg.
		sbi	LCDRW_PORT,LCDRW	;read
		rcall	LCD_pulseE		;Busy Flag read bit 7.
		mov	R16,R0
		rcall	LCD_pulseE		;lower nibble must read
		sbrc	R16,3			;Check busy flag
		 rjmp	LCDWait0


		lds	R16,LCDDAT_DIR		;LCD Data lines outputs
		ori	R16,LCDDAT_Mask
		sts	LCDDAT_DIR,R16
		lds	R16,LCDDAT_PORT
		andi	R16,255-LCDDAT_Mask	;All zero
		sts	LCDDAT_PORT,R16
		pop	R16
		ret


;*****************************************************
;** LCD_SendCmd
;**
;**  In: R16 - Command byte
;**
;**  Out: -
;**
;**
;** Alt: R0, R1, R16, R17
;**
;** Description:
;** Routine to write a command to the instruction register.
;
LCD_SendCmd:
		rcall	LCD_WaitBusy
		mov	R1,R16
		swap	R16
		andi	R16,LCDDAT_Mask		;send upper nibble first
		lds	R17,LCDDAT_PORT
		andi	R17,255-LCDDAT_Mask
		or	R17,R16
		sts	LCDDAT_PORT,R17
		cbi	LCDRS_PORT,LCDRS	;Set to Command Reg.
		cbi	LCDRW_PORT,LCDRW	;Write
		rcall	LCD_PulseE		;Latch upper nibble

		mov	R16,R1
		andi	R16,LCDDAT_Mask		;send lower nibble
		lds	R17,LCDDAT_PORT
		andi	R17,255-LCDDAT_Mask
		or	R17,R16
		sts	LCDDAT_PORT,R17
		cbi	LCDRS_PORT,LCDRS	;Set to Command Reg.
		cbi	LCDRW_PORT,LCDRW	;Write
		rcall	LCD_PulseE		;Latch lower nibble
		ret


;*****************************************************
;** LCD_SendChar
;**
;**  In: R16 - character code
;**
;**  Out: -
;**
;**
;** Alt: R0,R1, R16, R17
;**
;** Description:
;** Routine to write a character to the data register.
;
LCD_SendChar:
		rcall	LCD_WaitBusy
		mov	R1,R16
		swap	R16
		andi	R16,LCDDAT_Mask		;send upper nibble first
		lds	R17,LCDDAT_PORT
		andi	R17,255-LCDDAT_Mask
		or	R17,R16
		sts	LCDDAT_PORT,R17
		sbi	LCDRS_PORT,LCDRS	;Set to data Reg.
		cbi	LCDRW_PORT,LCDRW	;Write
		rcall	LCD_PulseE		;Latch upper nibble
		mov	R16,R1
		andi	R16,LCDDAT_Mask		;send lower nibble
		lds	R17,LCDDAT_PORT
		andi	R17,255-LCDDAT_Mask
		or	R17,R16
		sts	LCDDAT_PORT,R17
		sbi	LCDRS_PORT,LCDRS	;Set to Data Reg.
		cbi	LCDRW_PORT,LCDRW	;Write
		rcall	LCD_PulseE		;Latch lower nibble
		ret


;*****************************************************
;** LCD_Goto
;**
;**  In: R16 - position
;**		0x00 - 1.row, 1.col
;**		0x40 - 1.row, 2.col
;**
;**  Out: -
;**
;**
;** Alt: R0, R1, R16, R17
;**
;** Description:
;** 
;
LCD_Goto:
		ori	R16,0b10000000		;Set address Command
		rcall	LCD_SendCmd
		ret


;*****************************************************
;** LCD_PrnFLASHStr
;**
;**  In: Z+RAMP - start address of string
;**
;**  Out: -
;**
;**
;** Alt: R0, R1, R16, R17
;**
;** Description:
;** Print a null terminated string to LCD
;
LCD_PrnFLASHStr:
		elpm	R16,Z+
		tst	R16
		breq	LCD_PrnFLSH0
		rcall	LCD_SendChar
		rjmp	LCD_PrnFLASHStr
LCD_PrnFLSH0:
		ret