;
; ToUpper_USART.asm
;
; Created: 24/04/2018 13:29:04
; Author : 1418
;

;*********************************************************************************************
;******************** Const Definitions,  Precompiler sentences ******************************
;*********************************************************************************************
.EQU lowercase_a = 97	;ASCII for 'a'
.EQU lowercase_z = 122	;ASCII for 'z'
.EQU TOUPPER = 32		;to be subtracted from the lowercase to get the uppercase
.EQU minus = 45			;Letra guion "-"


.EQU Clock = 16000000		;processor’s clock frequency, Hz
.EQU Baud = 9600			;desired serial port baud rate (bits per second)
.EQU UBRRvalue = Clock/(Baud*16) -1		;calculates value to be put in UBRR0H:L

;*********************************************************************************************
;******************** Main VARs **************************************************************
;*********************************************************************************************
.DSEG

;*********************************************************************************************
;******************** Main Program ***********************************************************
;*********************************************************************************************
.CSEG
.ORG 0x00000			;reset interrupt vector
	jmp Init

.ORG 0x00032			;interrupt vectors for USART0
	jmp USART0_reception_completed
	reti
	reti

.ORG 0x00100			;leave room for IRQ vectors
Init:
	;configure USART0
	RCALL init_USART0
	rcall InitBPort

	SEI ;enable interrupts globally

	clr r16
Loop:
	out portb, r16
    rcall delay500ms
	com r16
    rjmp Loop

;*********************************************************************************************
;**************** End Main Program ***********************************************************
;*********************************************************************************************

;------- initialize USART0 as 9600baud, asynchronous, 8 data bits, 1 stop bit, no parity -----
;Especificaciones: https://appelsiini.net/2011/simple-usart-with-avr-libc/#registers
;                  http://microcontroladores-mrelberni.com/interrupcion-usart-avr/
init_USART0:
	PUSH R16
	LDI R16, LOW(UBRRvalue)
	STS UBRR0L, R16   ;load the low byte
	LDI R16, HIGH(UBRRvalue)
	STS UBRR0H, R16   ;load the low byte
	; enable receive and transmit, enable USART0 interrupts (UDR empty, Tx finished, Rx finished)
   ;ldi r16, (1<<RXEN0)|                                     (1<<RXCIE0)
	LDI R16, (1<<RXEN0)|(1<< TXEN0)|(0<<UDRIE0)|(0<< TXCIE0)|(1<< RXCIE0)
	STS UCSR0B, R16 ;set control register UCSR0B with the corresponding bits
	; configure USART 0 as asynchronous, set frame format: 8 data bits, 1 stop bit, no parity
	LDI R16, (0<<UMSEL00) |(1<<UCSZ01)|(1<< UCSZ00) |(0<< USBS0)|(0<<UPM01)|(0<< UPM00)
	STS UCSR0C, R16 ;set control register UCSR0C with the corresponding bits
	POP R16
	RET

;----USART0_reception_completed handler --------------------------------------------------
USART0_reception_completed:
 	PUSH r16			;this handler routine will be automatically called every 61msec (in this example)
	IN r16, SREG		;Backup SREG. MANDATORY in interrupt handler routines
	PUSH r16

	;do the desired periodic task here
	LDS r16, UDR0			;pick up the byte received and do anything with it
	CPI r16,lowercase_a		;'a'
	BRLT NotConvert			;not a lowercase letter
	CPI r16,lowercase_z+1	;'z'+1
	BRGE NotConvert			;not an lowercase letter
	SUBI r16, TOUPPER		;change to Uppercase
	STS UDR0, r16			;transmits the [modified] byte
	JMP USART0_reception_cont
	; Non conver. not lowercase letter. send "-" character
NotConvert:
	;LDI r16, minus
	STS UDR0, r16			;transmits the [modified] byte

USART0_reception_cont:
	POP r16
	OUT SREG, r16			;Recover SREG from the previous backup
	POP r16
	RETI ;RETI is MANDATORY when returning from an interrupt handling routine

;Funcion inicializar puerto B como salida
InitBPort:
	push r31
	LDI r31, 0xff
	OUT DDRB, r31
	pop r31
	ret

; Delay 3 200 000 cycles
; 200ms at 16 MHz
delay500ms:
    push r18
	push r19
	push r20
    ldi  r18, 41
    ldi  r19, 150
    ldi  r20, 128
L1: dec  r20
    brne L1
    dec  r19
    brne L1
    dec  r18
    brne L1
	pop r20
	pop r19
	pop r18
	ret

.EXIT