avr_242_multiplexing_led_drive_and_4x4_keypad_sampling.asm

Collected AVR assembler code samples to learn assembler. I use it in my classes.

		sbr flags,0x02		;make load 2 active
		rcall setrtc		;pickup new on time
		mov ld2hron,hiset	;and store
		mov ld2minon,loset
		cbr flags,0x10		;clear ld2on flag
		rjmp case6
setld2off:
		
		rcall setrtc		;pickup new on time
		mov ld2hroff,hiset	;and store
		mov ld2minoff,loset
		cbr flags,0x20		;clear ld2off flag
		rjmp case7

		
;****Multiplexing routine to display time and scan keypad every*****
;****second pass,used by all routines taking digits from hibyte 
;****and lobyte locations with each digit on for 5 ms

display:	ser temp		;clear display
		out PORTB,temp
;****Keypad scanning routine to update key flags*******************

keyscan:	cbr flags,0x40		;clear keyok flag
		ldi key,0x10		;set no key pressed value
		ser temp		;set keypad port high prior to
		out PORTB,temp		;reinitializing the port
		in temp,PORTD		;turn off LEDs and leave loads
		ori temp,0x0f		;untouched prior to
		out PORTD,temp		;key scan
		ldi temp,0x0f		;set columns output and
		out DDRB,temp		;rows input with pull-ups
		ldi temp,0xf0		;enabled and all columns
		out PORTB,temp		;low ready for scan
		ldi temp,20		;short settling time
tagain1:	dec temp
		brne tagain1
		sbis PINB,ROW1		;find row of keypress
		ldi key,0		;and set ROW pointer
		sbis PINB,ROW2
		ldi key,4
		sbis PINB,ROW3
		ldi key,8
		sbis PINB,ROW4
		ldi key,12
		ldi temp,0xF0		;change port B I/O to
		out DDRB,temp		;find column press
		ldi temp,0x0F		;enable pull ups and
		out PORTB,temp		;write 0s to rows
		ldi temp,20		;short settling time
tagain2:	dec temp
		brne tagain2		;allow time for port to settle
		clr temp
		sbis PINB,COL1		;find column of keypress
		ldi temp,0		;and set COL pointer
		sbis PINB,COL2
		ldi temp,1
		sbis PINB,COL3
		ldi temp,2
		sbis PINB,COL4
		ldi temp,3
		add key,temp		;merge ROW and COL for pointer
		cpi key,0x10		;if no key pressed 
		breq nokey		;escape routine, else
		ldi temp,0x10
		add key,temp		;change to table 2
		out EEAR,key		;send address to EEPROM (0 - 15)
		sbi EECR,EERE		;strobe EEPROM
		in key,EEDR		;read decoded number for true key
convert:	cpi key,10		;is it SET key ?
		brne notset		;no check next key
		set			;yes set T flag in status register
notset:		cpi key,11		;is key CLEAR?
		brne notclear		;no, check next key
		sbi PORTD,LOAD1		;yes, shut down all loads
		sbi PORTD,LOAD2
		cbr flags,0x03		;deactivate both loads
notclear:	cpi key,15		;is key LD1ON?
		brne notld1on		;no, check next key
		sbr flags,0x04		;yes, set LD1ON flag
notld1on:	cpi key,14		;is key LD1OFF?
		brne notld1off		;no, check next key
		sbr flags,0x08		;yes, set LD1OFF flag
notld1off:	cpi key,13		;is key LD2ON?
		brne notld2on		;no, check next key
		sbr flags,0x10		;yes, set LD2ON flag
notld2on:	cpi key,12		;is key LD2OFF?
		brne notld2off		;no, check next key
		sbr flags,0x20		;yes, set LD2OFF flag
notld2off:
	
;***Tactile feedback note generation routine*****************
;***provides a 4 kHz TONE to the piezo sounder for 5 ms*****

tactile:	cbr flags,0x80
		cbi PORTD,PZ		;turn on piezo
		ldi temp,125		;for a short time
t1again:	dec temp
		brne t1again
		sbi PORTD,PZ		;turn on piezo
		ldi temp,125		;for a short time
t2again:	dec temp
		brne t2again
		sbrs flags,ms5		;repeat for 5ms
		rjmp tactile	
notok:		cpi bounce,40
		brlo nokey
		sbr flags,0x40		;set bounce flag
nokey:		ser temp	
		out DDRB,temp		;reinitialize port B as all Outputs
		out PORTB,temp		;and clear LEDs

;***Display routine to multiplex all four LED digits****************

		cbi PORTD,A1		;turn digit 1 on
		mov temp,lobyte		;find low minute
digit1:	
		cbr flags,0x80		;clear 5 ms tick flag
		andi temp,0x0f		;mask high nibble of digit
		out EEAR,temp		;send address to EEPROM (0 - 15)
		sbi EECR,EERE		;strobe EEPROM
		in temp,EEDR		;read decoded number
		sbrs flash,clear	;flash every 1/2 second
		or temp,mask		;flash digit if needed
		out PORTB,temp		;write to LED for 5 ms
led1:		sbrs flags,ms5		;5 ms finished?
		rjmp led1		;no, check again
		sbi PORTD,A1		;turn digit 1 off
		ser temp		;clear display
		out PORTB,temp
		cbi PORTD,A2		;
		mov temp,lobyte		;find high minute
		swap temp
digit2:	
		cbr flags,0x80		;clear 5 ms tick flag
		andi temp,0x0f		;mask high nibble of digit
		out EEAR,temp		;send address to EEPROM (0 - 15)
		sbi EECR,EERE		;strobe EEPROM
		in temp,EEDR		;read decoded number
		sbrs flash,clear	;flash every 1/2 second
		or temp,mask		;flash digit if needed
		out PORTB,temp		;write to LED for 5 ms
led2:		sbrs flags,ms5		;5 ms finished?
		rjmp led2		;no, check again
		sbi PORTD,A2		;
		ser temp		;clear display
		out PORTB,temp
		cbi PORTD,A3		;
		mov temp,hibyte
digit3:	
		cbr flags,0x80		;clear 5 ms tick flag
		andi temp,0x0f		;mask high nibble of digit
		out EEAR,temp		;send address to EEPROM (0 - 15)
		sbi EECR,EERE		;strobe EEPROM
		in temp,EEDR		;read decoded number
		sbrs second,clear	;flash colon
		andi temp,0x7f
		sbrs flash,clear	;flash every 1/2 second
		or temp,mask		;flash digit if needed
		out PORTB,temp		;write to LED for 5 ms
led3:		sbrs flags,ms5		;5 ms finished?
		rjmp led3		;no, check again
		sbi PORTD,A3
		ser temp		;clear display
		out PORTB,temp
		cbi PORTD,A4		;
		mov temp,hibyte
		swap temp
		andi temp,0x0f		;is hi hour zero?
		brne digit4
		ldi temp,0xff		;yes,blank hi hour
digit4:	
		cbr flags,0x80		;clear 5 ms tick flag
		andi temp,0x0f		;mask high nibble of digit
		out EEAR,temp		;send address to EEPROM (0 - 15)
		sbi EECR,EERE		;strobe EEPROM
		in temp,EEDR		;read decoded number
		sbrs flash,clear	;flash every 1/2 second
		or temp,mask		;flash digit if needed
		out PORTB,temp		;write to LED for 5 ms
led4:		sbrs flags,ms5		;5 ms finished?
		rjmp led4		;no, check again
		sbi PORTD,A4
		ser temp		;clear display
		out PORTB,temp
		tst mask		;is flash complete?
		breq outled		;yes, exit
		cpi blink,50		;is blink time done?
		brlo outled		;no, exit 
		clr blink		;yes, clear blink rate counter
		com flash		;and invert flash byte
outled:		ret



		
;****Function to Set RTC/on-off hours and minutes from keypad
;****returns with minutes in 'loset' and hours in'hiset'
		
setrtc:		ser mask		;set flashing display
		ldi hibyte,0xdf		;place 'n' in hi hour
		ser lobyte		;and blank in lo hr & minutes
hihrus:		clr bounce
bounce1:	rcall display		;display and check keypad
		sbrs flags,keyok
		rjmp bounce1
		cbr flags,0x40		;clear keyok flag
		cpi key,0x03		;is high hour > 2
		brsh hihrus		;yes, read key again
hihrok:					;no, valid entry
		swap key		;move hihour to hi nibble
		mov hiset,key		;and store in hours
		ldi hibyte,0x0d		;place 'n' in lo hour
		add hibyte,hiset	;merge hihour and 'n'
lohrus:		clr bounce
bounce2:	rcall display		;display and check keypad
		sbrs flags,keyok	;is key stable?
		rjmp bounce2		;no try again
		cbr flags,0x40		;yes, clear keyok flag
		mov temp,hibyte		;check that total hours
		andi temp,0xf0		;are not > 24
		add temp,key
		cpi temp,0x24		;is hour>24?
		brsh lohrus		;yes, read key again
		add hiset,key		;no, merge hi and lo hours
lohrok:		
		mov hibyte,hiset	;display hours as set
		ldi lobyte,0xdf		;place 'n' in hi minutes
himinus:	clr bounce
bounce3:	rcall display		;display and check keypad
		sbrs flags,keyok
		rjmp bounce3
		cbr flags,0x40		;clear keyok flag
		cpi key,6		;is hi minutes >5
		brsh himinus		;no, read key again
lominok:	
		swap key		;move himin to hi nibble
		mov loset,key		;and store in minutes
		ldi lobyte,0x0d		;place 'n' in lo minutes
		add lobyte,loset	;merge with hi minute
lominus:	clr bounce
bounce4:	rcall display		;display and check keypad
		sbrs flags,keyok
		rjmp bounce4
		cbr flags,0x40		;clear keyok flag
		cpi key,10		;is key >9
		brsh lominus		;no, read key again
		add loset,key		;yes, merge hi and lo minutes
		clr mask		;clear digits flash
		ret			;and return with time set

;****Timer Overflow Interrupt service routine******************************
;****Updates 5 ms, flash and debounce counter to provide RTC time reference

tick:		
		in status,SREG		;preserve status register
		inc tock		;add one to 5 ms 'tock' counter
		inc blink		;and blink rate counter
		inc bounce		;and bounce rate delay
		sbr flags,0x80		;set 5 ms flag for display time
		cpi tock,200		;is one second up?
		breq onesec		;yes, add one to seconds
		nop			;balance interrupt time
		rjmp nosecond		;no, escape
onesec:		inc second		;add one to seconds
		clr tock		;clear 5 ms counter
nosecond:	ldi timer,176		;reload timer 
		out TCNT0,timer
		out SREG,status		;restore status register
		reti			;return to main