;AT90S8515 version created by Rafael Alcocer, ralcocer@imedicalpr.com
.nolist
.include "8515def.inc"
.list 
.def charcount =r1 ;Number of characters displayed on line being written
.def delay2 =r16 ;Temporary register.
.def temp =r17 ;Temporary register.
.def temp1 =r18
.def outchar =r19 ;Char to send by UART.
.def inchar =r20 ;Char received by UART
.def flagreg =r21 ;Flags
.def charbuf =r22 ;Char read from circular buffer
; YL ;UART circular buffer write pointer.
.def gpcount =r23 ;General purpose counter
; ZL ;UART circular buffer read pointer
; XL ;16 char line buffer pointer
.equ lbufsiz =$10
.equ circbufsiz =$0F 
.equ OE =8 ;Bit 3 port B display enable (also directly addressed).
.equ RS =4 ;Bit 2 in port B display register select (also directly 
;adressed)
.equ cbufbot =$60 ;Bottom of circular UART receive buffer.
.equ cbuftop =$67 ;Top of circular UART receive buffer.
.equ lbufbot =$70 ;Bottom of display line buffer.
.equ lbuftop =$7F ;Top of display line buffer.

;Baudrate Calculation
.equ clock = 4000000 ;clock frequency
.equ baudrate = 9600 ;choose a baud rate
.equ baudconstant = (clock/(16*baudrate))-1

;Flagreg bit assignments
; bit 0 Pending linefeed if high.
; bit 1 
; bit 2
; bit 3
; bit 4
; bit 5
; bit 6
; bit 7
;Memory usage:
;Ring buffer from $60 through $67
;Line buffer from $70 to $7F
;******************************
.cseg
.org $00


rjmp start ; Reset 
rjmp start 
rjmp start 
rjmp start 
rjmp start 
rjmp start 
rjmp start
rjmp start
rjmp UartRecInt ;UART interrupt 
rjmp UartRecInt ;interrupt 
;rjmp UartRecInt ;UART interrupt 


HelloString: ;TEXT TO BE TYPED ON FIRST LINE WHEN POWER IS APPLIED
.db "8515 LCD 1002031B"
.db 00,00 
crlf:
.db $0A,$0D
.db 00,00
message1:
.db "Press any key",0
message2:
.db "please (1-16)",0
message3:
.db "You pressed",0 
message4:
.db "key:",0
start:
clr XH
clr YH
clr ZH

ldi temp,low(RAMEND) ;Init Stack Pointer 
out SPL,temp
ldi temp,high(RAMEND)
out SPH,temp 
ldi temp,0b00000011 ;Weak pullups on inputs
out PORTB,temp 
ldi temp,0b11111100 
out DDRB,temp ;PORTB = all outputs except bits 0,1 
ldi temp,0b11111111 ;Weak pullups on inputs 
out PORTD,temp 
ldi temp,0b00000000 ;PORTD - all inputs 
ldi flagreg,$00 ;Set all flags to zero. 
ldi temp,$00 
mov charcount,temp 
rcall ClearLineBuffer ;Initialize line buffer. 
rcall DisplayInit 
ldi temp,baudconstant 
out ubrr,temp ;load baudrate 
sbi ucr,txen ;Enable the UART transmitter 
sbi ucr,rxen ;Enable the receiver.. 
rcall sendhello ;write line 1 power-up information
rcall Hometwo ;Position cursor for input on line two. 
ldi YL,cbufbot ;Set Y and Z circ buff pointers to bottom. 
ldi ZL,cbufbot 
sbi UCR,7 ;Emable UART Interrupt. 
sei ;Global interrupt flag set (enabled).

forever: ;Waiting for new data from circular buffer 

;Get waiting char from circular buffer if there is one. 
cp YL,ZL ;Is circular buffer read pointer already pointing to latest entry? 
breq Buffempty ;If so, there is no new data in the buffer. 
ld charbuf,Z+ ;If pointers are not equal, then read next char in buffer. 
cpi ZL,cbuftop + 1 ;Advance circular buffer read pointer to next value. 
brne NoZeroZL ;If end of buffer, wrap around to start of buffer. 
ldi ZL,cbufbot

NoZeroZL: ;Handle the new character as either a control char or a displayable char. 
;If bufchar is a control char,test for CR and LF 
cpi charbuf,$1F ;If not a control char branch to displayable char routine.. 
brpl ItsDisplayable 
cpi charbuf,$0D ;If this is a carriage return character, 
brne noCR ;Set cursor to start of bottom line. 
ldi XL,lbufbot ;Its a CR so set ponters back to start of line. 
ldi temp,$00 
mov charcount,temp 

rcall hometwo ;Put cursor back in first column of line two. 

noCR:

cpi charbuf,$0A ;If its a linfeed char then 
brne NotALineFeed ;set linfeed pending flag. 
ori flagreg,0b00000001

NotALineFeed: 
rjmp Buffdone

ItsDisplayable: ;If not a control char then do line feed if pending then 
;write to display and to line buffer. 
sbrc flagreg,0 ;If linefeed i spending, then do it 
rcall linefeed 
cpi XL,lbuftop+1 ;Don't store if buffer at limit. 
breq Xfull 
st X+,charbuf 
mov temp,charbuf 
rcall DATA_DISPLAY

Xfull: 

Buffdone:

Buffempty: 
rjmp forever 

SendHello: ;Send HelloString

rcall Homeone 
ldi ZH,high(2*HelloString) ; Load high part of byte address into ZH 
ldi ZL,low(2*HelloString) ; Load low part of byte address into ZL

moretosend: 
lpm ; Load byte from program memory into r0 
tst r0 ; Check if we've reached the end of the message 
breq finishsendstering ; If so, return 
mov temp,r0 
rcall DATA_DISPLAY
adiw ZL,1 ; Increment Z registers
rjmp moretosend

finishsendstering: 
ret 

linefeed: ;Handle a linefeed char 
;Clear line 1 (top line), copy line two to line one, clear 
;line two, the position the cursor in first column of line two.
push gpcount ;*****
push YL ;******
push ZL ;*******
rcall hometwo ;Put cursor at start of line 2 so it can be cleared. 
ldi gpcount,$10 ;Number of chars in line.****

clearmore: 
ldi temp,$20 ;Fill line with spaces (erase).

rcall DATA_DISPLAY 
dec gpcount 
brne clearmore

rcall homeone ;Copy line buffer to line 1, reset XL to bottom. 
ldi XL,lbufbot 
ldi temp,$00 
mov charcount,temp

MoreToCopy: 
ld temp,X+ 
rcall DATA_DISPLAY 
cpi XL,lbuftop + 1 
brne MoreToCopy 
rcall ClearLineBuffer 
ldi flagreg,$0b11111100 ;Clear linefeed pending and enable flagsb.
;*************************************************
;Added to reset the buffers ,counter and flag
;************************************************* 
rcall hometwo 
ldi gpcount,$00 ;********
pop ZL ;*****
POP YL ;*****
pop gpcount ;****

ldi flagreg,$00 ;******Set all flags to zero. 
ldi temp,$00 ;******
mov charcount,temp 
ret ;Done 
;************************************************* 

ClearLineBuffer: ;Fill line buffer with spaces, set XL to bottom. 
ldi XL,lbufbot 
ldi temp,$00 
mov charcount,temp 
ldi temp,$20

MoreToSpace: 
st X+,temp 
cpi XL,lbuftop + 1 
brne MoreToSpace 
ldi XL,lbufbot 
ret

recchar:
;sbi ucr,rxen ; set receiver bit 
sbis usr,rxc ;Wait for a char. 
rjmp recchar 
in inchar,udr ;Read the char. 
rjmp emitchar 
;cbi ucr,rxen ;clear register
ret



emitchar:
mov outchar,inchar 
sbis usr,udre ;wait until the register is cleared 
rjmp emitchar 
out udr,outchar ;send the byte 
ret ;go back


HomeOne: ;Home cursor to start of first top line of display. 
ldi temp,$80 
rcall COMMAND_DISPLAY 
ret

HomeTwo: ;Home cursor to start of bottom line of display 
ldi temp,$C0 
rcall COMMAND_DISPLAY 
ret 

;************************************************
;
; Write command to display
; command word in temp
; built in 50 usec delay; by Richard Hosking
;************************************************

COMMAND_DISPLAY: 
mov temp1,temp ;Copy data to temp1 
andi temp,0b11110000 ;mask off lower 4 bits, make OE and RS low 
sbr temp,OE ;OE bit high 
out PORTB,temp ;write upper 4 bits to display 
nop ;wait 1 usec total command 
nop ; Stabilize line 
nop ;Added by DC to bring up to 1 us for 4 mHz clock 
nop ;Added by DC to bring up to 1 us for 4 mHz clock 
cbi PORTB,3 ;OE low to clock in data 
swap temp1 ;get lower 4 bits 
andi temp1,0b11110000 ; mask off lower 4 bits, make OE and RS low 
sbr temp1,OE ;OE high 
out PORTB,temp1 ;write lower 4 bits to LCD ; 
nop ; 
nop 
nop ;Added by DC to bring up to 1 us for 4 mHz clock 
nop ;Added by DC to bring up to 1 us for 4 mHz clock 
; 
cbi PORTB,3 ;OE low to clock in data 
ldi temp,100 ;Wait about 50 usec 
D4: 
dec temp 
brne D4 
ret ; return
;******************************************************
;
; Writes data to display; incorporates 50 usec delay; data in temp
; by Richard Hosking
;********************************************************
DATA_DISPLAY: 
mov temp1,temp ; Copy data to temp1 
andi temp,0b11110000 ; mask off lower 4 bits 
sbr temp,OE ; OE bit high 
sbr temp,RS ; data/command bit high 
out PORTB,temp ; write upper 4 bits to display 
nop ; wait 1 usec total command 
nop ; Stabilize line 

cbi PORTB,3 ; OE low to clock in data; 
swap temp1 ; get lower 4 bits 
andi temp1,0b11110000 ; mask off lower 4 bits 
sbr temp1,OE ; OE high 
sbr temp1,RS 
out PORTB,temp1 ; write lower 4 bits to LCD 
nop ; 
nop 
cbi PORTB,3 ; OE low to clock in data; 
ldi temp,100 ; Wait about 50 usec ; 
ldi temp,200 ; Wait about 50 usec 
D5: 
dec temp 
brne D5 
ret ; return

;*********************************************************************
; Delay 2 msec with a 4MHz clock
;*********************************************************************
WAIT_2msec: 
ldi temp1,$0B 

D24002: 
ldi Delay2,$FF

D24001: 
dec Delay2 
brne D24001 
dec temp1 
brne D24002 
ret
;*************************************************************************
; Display setup
; Port B bit 3 OE Enable - clocks on neg transition
; 2 RS Register Select
; command=0, data=1

; bits 4-7 data 4 bits, high nibble first
; ASCII format
; RW grounded (write) 

; Note that some commands take up to 1.6 msec for display to implement
; at a nominal display clock rate of 250 KHz; Display initialize routine after power up
; by Richard 
;************************************************************************
DisplayInit: ;Initialize Display 
ldi temp,50 
;Wait at least 15msec after
D1: ;powerup before writing 
rcall WAIT_2msec ;to display
dec temp 
brne D1 
ldi temp,0b00111000 ;System set 
out PORTB,temp 
nop 
nop ;Data write cycle must be >1000usec 
cbi PORTB,3 ;OE low to clock in data; 
rcall WAIT_2msec ;Wait 4 msec rcall WAIT_2msec
;
ldi temp,0b00111000 ;System set 
out PORTB,temp 
nop 
nop ; Data write cycle must be >1000usec 
cbi PORTB,3 ; OE low to clock in data; 
rcall WAIT_2msec ; wait at least 100usec
ldi temp,0b00111000 ;System set 
out PORTB,temp 
nop ; 
nop ; 
cbi PORTB,3 ; OE low to clock in data 
rcall WAIT_2msec ; Wait at least 40usec (2 msec) 
ldi temp,0b00101000 ; Function set 4 bit mode, 2 lines 5X7 pixels 
rcall COMMAND_DISPLAY ; write to display -first write sets 4 bit 
; Second function set added by DC 
ldi temp,0b00101000 ; Function set 4 bit mode, 2 lines 5X7 pixels 
rcall COMMAND_DISPLAY ; write to display -second write to set N and F 
ldi temp,0b00001000 ;Display off, cursor off 
; blink off 
rcall COMMAND_DISPLAY ; 
ldi temp,0b00000001 ; Display clear 
rcall COMMAND_DISPLAY 
rcall WAIT_2msec ; Need to wait 1.6 msec after clear; 
ldi temp,0b00000110 ; Entry mode set 
; Increment RAM, dont shift display 
rcall COMMAND_DISPLAY ; 
ldi temp,0b00001110 ; Display on, cursor on ,blink off 
rcall COMMAND_DISPLAY; 
rcall WAIT_2msec ; Need to wait 1.6 msec after clear 
ret

UartRecInt:
;Uart interrupt service -Write received char into a circular buffer 
push temp 
rcall recchar ;Get the char from the UART. 
st Y+,inchar 
cpi YL,cbuftop + 1 
brne NoZeroYL 
ldi YL,cbufbot

NoZeroYL: 
pop temp 
reti