.include "m8def.inc"

.def zeichen = r16
.def temp = r19

.equ F_CPU = 8000000                            ; Systemtakt in Hz
.equ BAUD  = 38400                               ; Baudrate
 
; Berechnungen
.equ UBRR_VAL   = ((F_CPU+BAUD*8)/(BAUD*16)-1)  ; clever runden
.equ BAUD_REAL  = (F_CPU/(16*(UBRR_VAL+1)))      ; Reale Baudrate
.equ BAUD_ERROR = ((BAUD_REAL*1000)/BAUD-1000)  ; Fehler in Promille
 
.if ((BAUD_ERROR>10) || (BAUD_ERROR<-10))       ; max. +/-10 Promille Fehler
  .error "Systematischer Fehler der Baudrate grösser 1 Prozent und damit zu hoch!"
.endif

.org 0x0
rjmp main

.org URXCaddr                                   ; Interruptvektor für UART-Empfang
rjmp receive

main:
ldi temp, LOW(RAMEND)
out SPL, temp
ldi temp, HIGH(RAMEND)
out SPH, temp

ldi temp, 0xFF
out DDRC, temp

ldi temp, (1<<PD4) | (1<<PD5) | (1<<PD6)
out DDRD, temp

ldi temp, 0x00
out PORTC, temp
ldi temp, (0<<PD4) | (0<<PD5) | (0<<PD6)

ldi temp, (1<<PB1)
out DDRB, temp

rcall init_pwm
rcall init_lcd
rcall init_uart
sei
end:
rjmp end


wait:

ldi r17, 0xFF

loop:
ldi r18, 0xFF

inner_loop:
dec r18
brne inner_loop

dec r17
brne loop
ret

wait2:
rcall wait
rcall wait
ret

lcd_enable:
sbi PORTD, PD6
rcall wait2
cbi PORTD, PD6
ret

init_lcd:
ldi temp, 0b00000010
out PORTC, temp
rcall lcd_enable
ldi temp, 0b11110000
out PORTC, temp
rcall lcd_enable
swap temp
out PORTC, temp
rcall lcd_enable
ldi temp, 0b00010000
out PORTC, temp
rcall lcd_enable
swap temp
out PORTC, temp
rcall lcd_enable
ret 

lcd_write:
sbi PORTD, PD4
swap zeichen
out PORTC, zeichen
rcall lcd_enable
swap zeichen
out PORTC, zeichen
rcall lcd_enable
cbi PORTD, PD4
ret

lcd_clear:
ldi temp, 0b00010000
out PORTC, temp
rcall lcd_enable
swap temp
out PORTC, temp
rcall lcd_enable
ret

init_uart:
ldi     temp, HIGH(UBRR_VAL)
out     UBRRH, temp
ldi     temp, LOW(UBRR_VAL)
out     UBRRL, temp

ldi     temp, (1<<URSEL)|(1<<UCSZ0)| (1<<UCSZ1)
out     UCSRC, temp

sbi     UCSRB, RXCIE
sbi     UCSRB, RXEN
ret

cond_lcd_clear:
rcall lcd_clear
rjmp cond_lcd_clear_end

init_pwm:
ldi temp, 0x81
out TCCR1A, temp

ldi temp, 0x0d
out TCCR1B, temp

ldi temp, 0x00
out OCR1AH, temp

ldi temp, 0x80
out OCR1AL, temp

ret

receive:
cli
in zeichen, UDR
cpi zeichen, 0x0D
breq cond_lcd_clear
rcall lcd_write
cond_lcd_clear_end:
sei
reti