LCDDriver.asm

;***********************************************************
;*
;*	LCDDriver.asm	-	V2.0
;*
;*	Contains the neccessary functions to display text to a
;*	2 x 16 character LCD Display.  Additional functions
;*	include a conversion routine from an unsigned 8-bit
;*	binary number to and ASCII text string.
;*
;*	Version 2.0 - Added support for accessing the LCD 
;*		Display via the serial port. See version 1.0 for 
;*		accessing a memory mapped LCD display.
;*
;***********************************************************
;*
;*	 Author: David Zier
;*	   Date: March 17, 2003
;*	Company: TekBots(TM), Oregon State University - EECS
;*	Version: 2.0
;*
;***********************************************************
;*	Rev	Date	Name		Description
;*----------------------------------------------------------
;*	-	8/20/02	Zier		Initial Creation of Version 1.0
;*	A	3/7/03	Zier		V2.0 - Updated for USART LCD
;*
;*
;***********************************************************

;***********************************************************
;*	Internal Register Definitions and Constants
;*		NOTE: A register MUST be named 'mpr' in the Main Code
;*			It is recomended to use register r16.
;*		WARNING: Register r17-r22 are reserved and cannot be
;*			renamed outside of the LCD Driver functions. Doing
;*			so will damage the functionality of the LCD Driver
;***********************************************************
.def	wait = r17				; Wait Loop Register
.def	count = r18				; Character Counter
.def	line = r19				; Line Select Register
.def	type = r20				; LCD data type: Command or Text
.def	q = r21					; Quotient for div10
.def	r = r22					; Remander for div10

.equ	LCDLine1 = $80			; LCD Line 1 select command
.equ	LCDLine2 = $c0			; LCD Line 2 select command
.equ	LCDClear = $01			; LCD Clear Command
.equ	LCDHome = $02			; LCD Set Cursor Home Command
.equ	LCDPulse = $08			; LCD Pulse signal, used to simulate 
								; write signal

.equ	LCDCmd = $00			; Constant used to write a command 
.equ	LCDTxt = $01			; Constant used to write a text character

.equ	LCDMaxCnt = 16			; Maximum number of characters per line
.equ	LCDLn1Addr = $0100		; Beginning address for Line 1 data
.equ	LCDLn2Addr = $0110		; Beginning address for Line 2 data

;-----------------------------------------------------------
;***********************************************************
;*	Public LCD Driver Suboutines and Functions
;*		These functions and subroutines can be called safely 
;*		from within any program
;***********************************************************
;-----------------------------------------------------------


;*******************************************************
;* SubRt: 	LCDInit
;* Desc: 	Initialize the Serial Port and the Hitachi 
;*			Display 8 Bit inc DD-RAM 
;*			Pointer with no features
;*			- 2 LInes with 16 characters
;*******************************************************
LCDInit:
		push	mpr				; Save the state of machine
		in		mpr, SREG		; Save the SREG
		push	mpr				;
		push	wait			; Save wait

		; Setup the Communication Ports
		; Port B: Output
		; Port D: Input w/ internal pullup resistors
		; Port F: Output on Pin 3
		ldi		mpr, $00		; Initialize Port B for outputs
		out		PORTB, mpr		; Port B outputs high
		ldi		mpr, $ff		; except for any overrides
		out		DDRB, mpr		;
		ldi		mpr, $00		; Initialize Port D for inputs
		out		PORTD, mpr		; with Tri-State
		ldi		mpr, $00		; except for any overrides
		out		DDRD, mpr		;
		ldi		mpr, $00		; Initialize Port F Pin 3 to
		sts		PORTF, mpr		; output inorder to twiddle the
		ldi		mpr, (1<<DDF3)	; LCD interface
		sts		DDRF, mpr		; Must NOT override this port

		; Setup the Serial Functionality
		; SPI Type: Master
		; SPI Clock Rate: 2*1000.000 kHz
		; SPI Clock Phase: Cycle Half
		; SPI Clock Polarity: Low
		; SPI Data Order: MSB First
		ldi		mpr, (1<<SPE|1<<MSTR)
		out		SPCR, mpr		; Set Serial Port Control Register
		ldi		mpr, (1<<SPI2X)
		out		SPSR, mpr		; Set Serial Port Status Register

		; Setup External SRAM configuration
		; $0460 - $7FFF / $8000 - $FFFF
		; Lower page wait state(s): None
		; Uppoer page wait state(s): 2r/w
		ldi		mpr, (1<<SRE)	; 
		out		MCUCR, mpr		; Initialize MCUCR
		ldi		mpr, (1<<SRL2|1<<SRW11)
		sts		XMCRA, mpr		; Initialize XMCRA
		ldi		mpr, (1<<XMBK)	;
		sts		XMCRB, mpr		; Initialize XMCRB
		
		; Initialize USART0
		; Communication Parameter: 8 bit, 1 stop, No Parity
		; USART0 Rx: On
		; USART0 Tx: On
		; USART0 Mode: Asynchronous
		; USART0 Baudrate: 9600
		ldi		mpr, $00		;
		out		UCSR0A, mpr		; Init UCSR0A
		ldi		mpr, (1<<RXEN0|1<<TXEN0)
		out		UCSR0B, mpr		; Init UCSR0B
		ldi		mpr, (1<<UCSZ01|1<<UCSZ00)
		sts		UCSR0C, mpr		; Init UCSR0C
		ldi		mpr, $00		;
		sts		UBRR0H, mpr		; Init UBRR0H
		ldi		mpr, $67		;
		out		UBRR0L, mpr		; Init UBRR0L

		; Initialize the LCD Display
		ldi		mpr, 6			;
LCDINIT_L1:
		ldi		wait, 250		; 15ms of Display
		rcall	LCDWait			; Bootup wait
		dec		mpr				;
		brne	LCDINIT_L1		;

		ldi		mpr, $38		; Display Mode set
		rcall 	LCDWriteCmd		; 
		ldi		mpr, $08		; Display Off
		rcall	LCDWriteCmd		;
		ldi		mpr, $01		; Display Clear
		rcall	LCDWriteCmd		;
		ldi		mpr, $06		; Entry mode set
		rcall	LCDWriteCmd		;
		ldi		mpr, $0c		; Display on
		rcall	LCDWriteCmd		;
		rcall	LCDClr			; Clear display

		pop		wait			; Restore wait
		pop		mpr				; Restore SREG
		out		SREG, mpr		;
		pop		mpr				; Restore mpr
		ret						; Return from subroutine

;*******************************************************
;* Func:	LCDWrite
;* Desc:	Generic Write Function that writes both lines
;*			of text out to the LCD
;*			- Line 1 data is in address space $0100-$010F
;*			- Line 2 data is in address space $0110-$010F
;*******************************************************
LCDWrite:
		rcall LCDWrLn1			; Write Line 1
		rcall LCDWrLn2			; Write Line 2
		ret 					; Return from function

;*******************************************************
;* Func:	LCDWrLn1
;* Desc:	This function will write the first line of 
;*			data to the first line of the LCD Display
;*******************************************************
LCDWrLn1:
		push 	mpr				; Save mpr
		push	ZL				; Save Z pointer
		push	ZH				;
		push	count			; Save the count register
		push	line			; Save the line register
								
		ldi		ZL, low(LCDLn1Addr)
		ldi		ZH, high(LCDLn1Addr)		 
		ldi		line, LCDLine1	; Set LCD line to Line 1
		rcall	LCDSetLine		; Restart at the beginning of line 1
		rcall	LCDWriteLine	; Write the line of text

		pop		line
		pop		count			; Restore the counter
		pop		ZH				; Restore Z pointer
		pop		ZL				;
		pop 	mpr				; Restore mpr
		ret						; Return from function

;*******************************************************
;* Func:	LCDWrLn2
;* Desc:	This function will write the second line of 
;*			data to the second line of the LCD Display
;*******************************************************
LCDWrLn2:
		push 	mpr				; Save mpr
		push	ZL				; Save Z pointer
		push	ZH				;
		push	count			; Save the count register
		push	line			; Save the line register
								
		ldi		ZL, low(LCDLn2Addr)
		ldi		ZH, high(LCDLn2Addr)		 
		ldi		line, LCDLine2	; Set LCD line to Line 2
		rcall	LCDSetLine		; Restart at the beginning of line 2
		rcall	LCDWriteLine	; Write the line of text

		pop		line
		pop		count			; Restore the counter
		pop		ZH				; Restore Z pointer
		pop		ZL				;
		pop 	mpr				; Restore mpr
		ret						; Return from function

;*******************************************************
;* Func:	LCDClr
;* Desc:	Generic Clear Subroutine that clears both 
;*			lines of the LCD and Data Memory storage area
;*******************************************************
LCDClr:
		rcall	LCDClrLn1		; Clear Line 1
		rcall	LCDClrLn2		; Clear Line 2
		ret						; Return from Subroutine

;*******************************************************
;* Func:	LCDClrLn1
;* Desc:	This subroutine will clear the first line of 
;*			the data and the first line of the LCD Display
;*******************************************************
LCDClrLn1:
		push	mpr				; Save mpr
		push	line			; Save line register
		push	count			; Save the count register
		push	ZL				; Save Z pointer
		push	ZH				;
	
		ldi		line, LCDline1	; Set Access to Line 1 of LCD
		rcall	LCDSetLine		; Set Z pointer to address of line 1 data
		ldi		ZL, low(LCDLn1Addr)
		ldi		ZH, high(LCDLn1Addr)
		rcall	LCDClrLine		; Call the Clear Line function

		pop		ZH				; Restore Z pointer
		pop		ZL				;
		pop		count			; Restore the count register
		pop		line			; Restore line register
		pop		mpr				; Restore mpr
		ret						; Return from Subroutine

;*******************************************************
;* Func:	LCDClrLn2
;* Desc:	This subroutine will clear the second line of 
;*			the data and the second line of the LCD Display
;*******************************************************
LCDClrLn2:
		push	mpr				; Save mpr
		push	line			; Save line register
		push	count			; Save the count register
		push	ZL				; Save Z pointer
		push	ZH				;
	
		ldi		line, LCDline2	; Set Access to Line 2 of LCD
		rcall	LCDSetLine		; Set Z pointer to address of line 2 data
		ldi		ZL, low(LCDLn2Addr)
		ldi		ZH, high(LCDLn2Addr)
		rcall	LCDClrLine		; Call the Clear Line function

		pop		ZH				; Restore Z pointer
		pop		ZL				;
		pop		count			; Restore the count register
		pop		line			; Restore line register
		pop		mpr				; Restore mpr
		ret						; Return from Subroutine

;*******************************************************
;* Func:	LCDWriteByte
;* Desc:	This is a complex and low level function that
;*			allows any program to write any ASCII character
;*			(Byte) anywhere in the LCD Display.  There
;*			are several things that need to be initialized
;*			before this function is called:
;*		count - Holds the index value of the line to where
;*				the char is written, 0-15(39).  i.e. if 
;*				count has the value of 3, then the char is
;*				going to be written to the third element of
;*				the line.
;*		line  - Holds the line number that the char is going
;*				to be written to, (1 or 2).
;*		mpr	  - Contains the value of the ASCII character to 
;*				be written (0-255)
;*********************************************************
LCDWriteByte:
		push	mpr				; Save the mpr
		push	line			; Save the line
		push	count			; Save the count
								; Preform sanity checks on count and line
		cpi		count, 40		; Make sure count is within range
		brsh	LCDWriteByte_3	; Do nothing and exit function
		cpi		line, 1			; If (line == 1)
		brne	LCDWriteByte_1	; 
		ldi		line, LCDLine1	; Load line 1 base LCD Address
		rjmp	LCDWriteByte_2	; Continue on with function
LCDWriteByte_1:					
		cpi		line, 2			; If (line == 2)
		brne	LCDWriteByte_3	; Do nothing and exit function
		ldi		line, LCDLine2	; Load line 2 base LCD Address

LCDWriteByte_2:					; Write char to LCD
		add		line, count		; Set the correct LCD address
		rcall	LCDSetLine		; Set the line address to LCD
		rcall	LCDWriteChar	; Write Char to LCD Display		
		
LCDWriteByte_3:					; Exit Function
		pop		count			; Restore the count
		pop		line			; Restore the line
		pop		mpr				; Restore the mpr
		ret						; Return from function
		 
;*******************************************************
;* Func:	Bin2ASCII
;* Desc:	Converts a binary number into an ASCII 
;*			text string equivalent. 
;*			- The binary number needs to be in the mpr
;*			- The Start Address of where the text will
;*			 	be placed needs to be in the X Register
;*			- The count of the characters created are 
;*				added to the count register
;*******************************************************
Bin2ASCII:
		push	mpr				; save mpr
		push	r				; save r
		push	q				; save q
		push	XH				; save X-pointer
		push	XL				;

		; Determine the range of mpr
		cpi		mpr, 100		; is mpr >= 100
		brlo	B2A_1			; goto next check
		ldi		count, 3		; Three chars are written
		adiw	XL, 3			; Increment X 3 address spaces
		rjmp	B2A_3			; Continue with program
B2A_1:	cpi		mpr, 10			; is mpr >= 10
		brlo	B2A_2			; Continue with program
		ldi		count, 2		; Two chars are written
		adiw	XL, 2			; Increment X 2 address spaces
		rjmp	B2A_3			; Continue with program
B2A_2:	adiw	XL, 1			; Increment X 1 address space
		ldi		count, 1 		; One char is written

B2A_3:	;Do-While statement that converts Binary to ASCII
		rcall	div10			; Call the div10 function
		ldi		mpr, '0'		; Set the base ASCII integer value
		add		mpr, r			; Create the ASCII integer value
		st		-X, mpr			; Load ASCII value to memory
		mov		mpr, q			; Set mpr to quotiant value
		cpi		mpr, 0			; does mpr == 0
		brne	B2A_3			; do while (mpr != 0)

		pop		XL				; restore X-pointer
		pop		XH				;
		pop 	q				; restore q
		pop		r				; restore r
		pop		mpr				; restore mpr
		ret						; return from function

;-------------------------------------------------------
;*******************************************************
;* Private LCD Driver Functions and Subroutines
;*	NOTE: It is not recommended to call these functions
;*	      or subroutines, only call the Public ones.
;*******************************************************
;-------------------------------------------------------

;*******************************************************
;* Func:	LCDSetLine
;* Desc:	Change line to be written to 
;*******************************************************
LCDSetLine:
		push	mpr				; Save mpr
		mov		mpr,line		; Copy Command Data to mpr
		rcall	LCDWriteCmd		; Write the Command
		pop		mpr				; Restore the mpr
		ret						; Return from function

;*******************************************************
;* Func:	LCDClrLine
;* Desc:	Manually clears a single line within an LCD
;*			Display and Data Memory by writing 16 
;*			consecutive ASCII spaces $20 to both the LCD 
;*			and the memory.  The line to be cleared must
;*			first be set in the LCD and the Z pointer is
;*			pointing the first element in Data Memory
;*******************************************************
LCDClrLine:
		ldi		mpr, ' '		; The space char to be written
		ldi		count, LCDMaxCnt; The character count
LCDClrLine_1:
		st		Z+, mpr			; Clear data memory element
		rcall	LCDWriteChar	; Clear LCD memory element
		dec		count			; Decrement the count
		brne	LCDClrLine_1	; Continue untill all elements are cleared
		ret						; Return from function

;*******************************************************
;* Func:	LCDWriteLine
;* Desc:	Writes a line of text to the LCD Display.
;*			This routine takes a data element pointed to
;*			by the Z-pointer and copies it to the LCD 
;*			Display for the duration of the line.  The
;*			line the Z-pointer must be set prior to the 
;*			function call.
;*******************************************************
LCDWriteLine:
		ldi		count, LCDMaxCnt; The character count
LCDWriteLine_1:
		ld		mpr, Z+			; Get the data element
		rcall	LCDWriteChar	; Write element to LCD Display
		dec		count			; Decrement the count
		brne	LCDWriteLine_1	; Continue untill all elements are written
		ret						; Return from function

;*******************************************************
;* Func:	LCDWriteCmd
;* Desc:	Write command that is in the mpr to LCD 
;*******************************************************
LCDWriteCmd:
		push	type			; Save type register
		push	wait			; Save wait register
		ldi		type, LCDCmd	; Set type to Command data
		rcall	LCDWriteData	; Write data to LCD
		push	mpr				; Save mpr register
		ldi		mpr, 2			; Wait approx. 4.1 ms
LCDWC_L1:
		ldi		wait, 205		; Wait 2050 us
		rcall	LCDWait			;
		dec		mpr				; The wait loop cont.
		brne	LCDWC_L1		;
		pop		mpr				; Restore mpr
		pop		wait			; Restore wait register
		pop		type			; Restore type register
		ret						; Return from function

;*******************************************************
;* Func:	LCDWriteChar
;* Desc:	Write character data that is in the mpr
;*******************************************************
LCDWriteChar:
		push	type			; Save type register
		push	wait			; Save the wait register
		ldi		type, LCDTxt	; Set type to Text data
		rcall	LCDWriteData	; Write data to LCD
		ldi		wait, 16		; Delay 160 us
		rcall	LCDWait			;
		pop		wait			; Restore wait register
		pop		type			; Restore type register
		ret						; Return from function

;*******************************************************
;* Func:	LCDWriteData
;* Desc:	Write data or command to LCD 
;*******************************************************
LCDWriteData:
		out		SPDR, type		; Send type to SP
		ldi		wait, 2			; Wait 2 us
		rcall	LCDWait			; Call Wait function
		out		SPDR,mpr		; Send data to serial port
		ldi		wait, 2			; Wait 2 us
		rcall	LCDWait			; Call Wait function
		ldi		wait, LCDPulse	; Use wait temporarially to 
		sts		PORTF, wait		; to send write pulse to LCD
		ldi		wait, $00		;
		sts		PORTF, wait		;
		ret						; Return from function

;*******************************************************
;* Func:	LCDWait
;* Desc:	A wait loop that is 10 + 159*wait cycles or
;*			roughly wait*10us.  Just initialize wait
;*			for the specific amount of time in 10us 
;*			intervals.
;*******************************************************
LCDWait:push	mpr				; Save mpr
LCDW_L1:ldi		mpr, $49		; Load with a 10us value
LCDW_L2:dec		mpr				; Inner Wait Loop
		brne	LCDW_L2
		dec		wait			; Outer Wait Loop
		brne	LCDW_L1
		pop		mpr				; Restore mpr
		ret						; Return from Wait Function

;*******************************************************
;*	Bin2ASCII routines that can be used as a psuedo-
;*			printf function to convert an 8-bit binary
;*			number into the unigned decimal ASCII text
;*******************************************************

;***********************************************************
;* Func:	div10
;* Desc:	Divides the value in the mpr by 10 and 
;*			puts the remander in the 'r' register and
;*			and the quotiant in the 'q' register.
;*	DO NOT modify this function, trust me, it does
;*	divide by 10 :)  ~DZ		
;***********************************************************
div10:
		push	r0				; Save register

		; q = mpr / 10 = mpr * 0.000110011001101b
		mov		q, mpr			; q = mpr * 1.0b
		lsr		q				; q >> 2
		lsr		q				; q = mpr * 0.01b
		add		q, mpr			; q = (q + mpr) >> 1
		lsr		q				; q = mpr * 0.101b
		add		q, mpr			; q = (q + mpr) >> 3
		lsr		q
		lsr		q
		lsr		q				; q = mpr * 0.001101b
		add		q, mpr			; q = (q + mpr) >> 1
		lsr		q				; q = mpr * 0.1001101b
		add		q, mpr			; q = (q + mpr) >> 3
		lsr		q				
		lsr		q
		lsr		q				; q = mpr * 0.0011001101b
		add		q, mpr			; q = (q + mpr) >> 1
		lsr		q				; q = mpr * 0.10011001101b
		add		q, mpr			; q = (q + mpr) >> 4
		lsr		q
		lsr		q
		lsr		q
		lsr		q				; q = mpr * 0.000110011001101b

		; compute the remainder as r = i - 10 * q
		; calculate r = q * 10 = q * 1010b
		mov		r, q			; r = q * 1
		lsl		r				; r << 2
		lsl		r				; r = q * 100b
		add		r, q			; r = (r + q) << 1
		lsl		r				; r = q * 1010b
		mov		r0, r			; r0 = 10 * q
		mov		r, mpr			; r = mpr
		sub		r, r0			; r = mpr - 10 * q

		; Fix any errors that occur
div10_1:cpi		r, 10			; Compare with 10
		brlo	div10_2			; do nothing if r < 10
		inc		q				; fix qoutient
		subi	r, 10			; fix remainder
		rjmp	div10_1			; Continue until error is corrected

div10_2:pop		r0				; Restore registers
		ret						; Return from function