;;***************************************
;;***** RS-232 test on 4114 *************
;;***************************************
;Fully interrupt driven
;Strings can come from flash or RAM.

.include "c:\tmp\8535def.inc"

.def	ascii_1	=r1
.def	ascii_2	=r2
.def	ascii_3	=r3
.def	LF	=r4
.def	CR	=r5
.def	NULL	=r6


.def	temp	=r16	;temporary register
.def	count	=r17	;a counter to use in message
.def	savSREG	=r18	;save the status register
.def	TXbusy	=r19	;transmit busy flag
.def	RXchar	=r20	;a received character
.def	TXflash	=r21	;text to be sent is in flash if <>0
.def	ADCvalc	=r22
.def	temp2	=r23
.def	count_L	=r24
.def	count_H	=r25

.equ	baud96	=51	;9600 baud constant for 4Mhz crystal
.equ	go	='g' 	;0x67 ascii 'g'
.equ	stop	='s'	;0x73 ascii 's'
.equ	azero	='0'	;0x30 ascii '0'
.equ	counts	=300;


;**************************************
.dseg

;define variable strings to be tranmitted from RAM
cntstr:	.byte	3	;a two digit count + a zero terminate
ADCvals:.byte	counts	;300 consecutive ADC values

;**************************************
.cseg

.org $0000
	rjmp 	RESET	;reset entry vector
	reti		;Ext int req0	
	reti		;Ext int req1
	reti		;Timer/Counter2 compare match
	reti		;Timer/Counter2 Ovfl
	reti		;Timer/Counter1 Capture event
	rjmp	cp_match;Timer/Counter1 Compare match A
	reti		;Timer/Counter1 Compare match B
	reti		;Timer/Counter1 Ovfl
	reti		;Timer/Counter0 Ovfl
	reti		;Serial Transfer Complete
	reti 		;UART receive done
	rjmp	TXempty	;UART buffer empty
	reti;		;UART transmit done
	reti		;ADC conversion complete
	reti		;EEPROM ready
	reti		;Analog comparator


;define fixed strings to be tranmitted from flash- zero terminated
text:	.db	"The count is:",0x00 
crlf:	.db	0x0d, 0x0a, 0x00	;carrage return/line feed


RESET:	ldi	temp, LOW(RAMEND) ;setup stack pointer
	out 	SPL, temp
	ldi	temp, HIGH(RAMEND)
	out	SPH, temp

	;set up port B to run LEDS
	ser	temp		;set PORTB to be
	out	DDRB,temp	;all outputs to LEDs
	out	PORTB, temp

	out	DDRC, temp
	out	PORTC, temp	

	;clear ADCval register
	clr	ADCvalc
	

	;set up analog converter to read channel zero
	ldi	temp, 0
	out	ADMUX, temp

	;enable and set up ADC 
	;prescaler = 64
	;ADC free run mode disbaled
	;ADC start conversion off (turn on when ready)
	ldi	temp, 0b10000110
	out	ADCSR, temp
	
	
	
;start the ADC initalization
	ldi	temp, 0b01000000	;start A to D conversion	
	in	temp2, ADCSR
	or	temp, temp2	
	out	ADCSR, temp

;spin until the ADC is finished
rwait:  in      temp, ADCSR     ;wait for A to D done
        sbrc    temp, 6         ;by checking ADSC bit
        rjmp    rwait           ;this bit is cleared by the AtoD hardware
	
	clt			;clear t bit

	;wait for press
	clr	temp		;set PORTB to be
	out	DDRD,temp	;all inputs

	in	temp, PIND	;IN to PINs OUT to PORTs

	ldi	temp, 0xAA
	out	PORTB, temp

butt_wait:	
	sbic	PIND, 0		; check buttons, set state
	rjmp	butt_wait

	ldi	temp, 0x00
	out	PORTB, temp
	

;set up timers and match register 
	;enable compareA match register int
	ldi	temp, 0b00010000
	out	TIMSK, temp	

	;set match regs for fs=3000hz (2667ticks for fs=2999.6)
	ldi	temp, 0x0A	;set the match A register to
	out	OCR1AH, temp	;
	ldi	temp, 0x6B	;2667 = 0x0A6B
	out	OCR1AL, temp
	
	;set prescaler to 1 and clear on compare/match
	ldi	temp, 0b00001001	
	out	TCCR1B, temp	
	
	;initial conditions
	ldi	count,azero 	;ascii zero the count
	clr	TXbusy		;start out not busy on TX
	ldi	RXchar, go	;start out running

	;setup UART -- enable TXempty & RXdone int, and RX, TX pins
	ldi 	temp, 0b00001000
	out 	UCR, temp
	;set baud rate to 9600
	ldi	temp, baud96
	out	UBRR, temp
	;intialize text pointer BEFORE turning on interrupts
	;because RESET causes the TX empty flag to be SET
	ldi	ZL, LOW(ADCvals) ;do shift to convert word-addr to byte
	ldi 	ZH, HIGH(ADCvals)

	sei


	;capture 300 samples with ADC and place in SRAM
	clr	count_L
	clr	count_H

await:  
	brtc	await		;wait if t bit is cleared
	in      temp, ADCSR     ;wait for A to D done
	out	PORTC,temp
	sbrc    temp, 6         ;by checking ADSC bit
	rjmp    await           ;this bit is cleared by the AtoD hardware
	clt			;clear the t bit in the status register
	
	
	in	temp, ADCL	;read the voltage
	in	temp2, ADCH
	lsr	temp2		;double precision shift
	ror	temp		;right twice
	lsr	temp2
	ror	temp
	mov	ADCvalc, temp
	
	st	Z+, ADCvalc	
	;st	Z+, count_L

	ldi	temp, 1
	add	count_L, temp
	clr	temp
	adc	count_H, temp

	cpi	count_L, LOW(counts)
	brne	await
	cpi	count_H, HIGH(counts)
	brne	await
	
	;we're done!!! stop the clock to prevent futher ADC samples
	;set prescaler to 1 and clear on compare/match
	ldi	temp, 0b00001000	
	out	TCCR1B, temp	
	
	
	ldi	ZL, LOW(ADCvals)
	ldi	ZH, HIGH(ADCvals)
	clr	count_L
	clr	count_H

;300 vals now in SRAM, time to send 'em to the UART!!!
write_all:	
	
	
	ld	ADCvalc, Z+
	
	clr	ascii_1
	clr	ascii_2
	clr	ascii_3
	
	start_divide:
	cpi	ADCvalc,100
	brlo	hundreds_done
	inc	ascii_1
	subi	ADCvalc,100
	rjmp	start_divide

hundreds_done:
	cpi	ADCvalc,10
	brlo	tens_done
	inc	ascii_2
	subi	ADCvalc,10
	rjmp	hundreds_done

tens_done:
	cpi	ADCvalc,1
	brlo	divide_done
	inc	ascii_3
	dec	ADCvalc
	rjmp	tens_done
	
divide_done:
	mov	temp, ascii_1
	subi	temp,-azero
	mov	ascii_1,temp
	
	mov	temp, ascii_2
	subi	temp,-azero
	mov	ascii_2,temp
	
	mov	temp, ascii_3
	subi	temp,-azero
	mov	ascii_3,temp

	ldi	temp,0x0d
	mov	CR,temp
	ldi	temp,0x0a
	mov	LF,temp
	ldi	temp,0
	mov	NULL,temp




;now print three strings and wait for incoming character interrupt
TXloop:	

	
noreset:

	;set up the transmit pointer for the registers holding the ASCII digits
	ldi	YL, 1  ;shifted becuase pgm memory is words
	ldi	YH, 0 ;
	ld	r0, Y			 ;put the char in r0
	out	UDR, r0		;put the character in the UART buffer	
	ser	TXbusy		;and set the TX busy flag
	sbi	UCR, UDRIE	;enable the TXempty interrupt
	rcall	TXwait		;chill until done
	 	
	
	ldi	temp, 1
	add	count_L, temp
	clr	temp
	adc	count_H, temp

	cpi	count_L, LOW(counts)
	brne	write_all
	cpi	count_H, HIGH(counts)
	brne	write_all
	
	;write out some carrige returns
	ldi	temp, 0x0a
	mov	r1, temp
	mov	r2, temp
	mov	r3,temp
	clr	r4
	
	;set up the transmit pointer for the registers holding the ASCII digits
	ldi	YL, 1  ;shifted becuase pgm memory is words
	ldi	YH, 0 ;
	ld	r0, Y			 ;put the char in r0
	out	UDR, r0		;put the character in the UART buffer	
	ser	TXbusy		;and set the TX busy flag
	sbi	UCR, UDRIE	;enable the TXempty interrupt
	rcall	TXwait		;chill until done
	
	;no more to write!
	rjmp	halt	
	


;*****************************
;interrupt routines

; UART needs a character
TXempty:in	savSREG, SREG	;save processor status	
	
TXram: 	inc	YL		;get the next char from RAM
	ld	r0,Y
	tst	r0		;if char is zero then exit
	breq	TXend		
	out 	UDR, r0		;otherwise transmit it
	rjmp	TXexit		;exit until next char
TXend:	clr	TXbusy		;no more chars
	cbi	UCR, UDRIE	;clear the TXempty interrupt
TXexit:	out	SREG, savSREG	;restore proc status
	reti			;back to pgm



;*****************************
;subroutine

TXwait:	tst	TXbusy		;now wait for the tranmission to finish
	brne	TXwait
	ret

;**** timer 1 compare A match 
cp_match:
	in	savSREG, SREG

	ldi	temp, 0b01000000	;start A to D conversion	
	in	temp2, ADCSR
	or	temp, temp2	
	out	ADCSR, temp
	
	;inc	freq
	;out	PORTC,freq

					;sets the T flag in status reg
	out	SREG, savSREG
	set	
	reti	


halt:	
	rjmp	RESET