Microcontroller INTERFACING programs

Here some of the interfacing programs are given. Devices like 7-segment display, stepper motor, ADC, DAC, Keyboard are interfaced to 8951 microcontroller. Also wave generator, serial communication and interrupt programs are given.





PROGRAM TO INTERFACE 7-SEGMENT DISPLAY.

PROGRAM TO ROTATE STEPPER MOTOR USING 8255 PORTS.

PROGRAM TO INTERFACE ADC

PROGRAM TO GENERATE STAIRCASE WAVE USING DAC

PROGRAM TO GENERATE TRIANGLE WAVE USING DAC

PROGRAM TO GENERATE SINE WAVE OF 200Hz USING DAC.

PROGRAM TO FIND THE FREQUENCY OF A SQUARE WAVE

PROGRAM FOR SERIAL COMMUNICATION

TO GENERATE RECTANGLE WAVE OF 500 Hz WITH 60% DUTY CYCLE USING TIMER 1 MODE 1

TO GENERATE SQUARE WAVE OF 500 Hz USING TIMER 1 MODE 1

TO GENERATE SQUARE WAVE OF 10K Hz USING TIMER 1 MODE 2

PROGRAM TO INTERFACE KEYBOARD USING 8255 PORTS.

PROGRAM TO GENERATE REAL TIME CLOCK USING TIMER AND INTERRUPT.

PROGRAM TO INTERFACE 7-SEGMENT DISPLAY





Here 7-segment is connected to Port 1 of 8051 microcontroller. Here look up table is stored from the memory location 19H. To display any number first get the 7-segment equivalent code and then send to port 1.

mov r0,#19h
mov @r0,#0bfh
inc r0
mov @r0,#86h
inc r0
mov @r0,#0dbh
inc r0
mov @r0,#0cfh
inc r0
mov @r0,#0e6h
inc r0
mov @r0,#0edh
inc r0
mov @r0,#fdh
inc r0
mov @r0,#87h
inc r0
mov @r0,#0ffh
inc r0
mov @r0,#0e7h

again: mov a,#00h
up: mov r2,a

mov r0,#19h
add a,r0
mov r0,a
mov a,@r0
mov p1,a
mov r3,#255
here1: mov r1,#255
here: djnz r1,here
djnz r3,here1
mov a,r2
inc a
cjne a,#0ah,up
sjmp again

PROGRAM TO ROTATE STEPPER MOTOR USING 8255 PORTS





A stepper motor is a widely used device that translates electrical pulses into mechanical movement. The most common stepper motors have four coils. The stepper motor discussed here has 6 leads: 4 leads representing the four stator windings and 2 commons for the center tapped leads. As the sequence of power is applied to each stator winding, the rotor will rotate. One way to rotate stepper motor is energizing a coil at a time. So you have to transmit the sequence as shown bellow .


Step
Winding A
Winding B
Winding C
Winding C

1
1
0
0
0

2
0
1
0
0

3
0 0 1 0
4
0
0
0
1



mov a,#11h ;move 11 to acc

h3: mov p1,a ;send (acc) to port A

rr a ;rotate (acc) to right

mov r2,#50 ;delay

h1: mov r1,#255

h2: djnz r1,h2

djnz r2,h1

jmp h3

.end

PROGRAM TO INTERFACE ADC




Here ADC 0804 is connected to port1 of 8051.WR and INTR of ADC is connected to P3.4 and P3.5 respectively. Analog input is applied to pin 6 of ADC. Here WR is the start of conversion and INTR is the end of conversion. In this program if input voltage accedes certain range then 8255 sets corresponding bits


mov a,#80h

mov dptr,#2023h

movx @dptr,a

mov p1,#ffh ; configuring port 1 as i/p

start: clr p3.4 ; low to high signal to WR, start of conversion

setb p3.4

here3: jb p3.5,here3 ; check whether conversion is over, pin-INTR

mov a,p1

mov r5,a

mov r6,a

lcall 66d3h

mov dptr,#2020h

mov a,r5

subb a,#cch ; check whether i/p is greater than 4V

jc L4v ; jump if input is less than 4V
mov a,#10h ; send high signal to 5th line

movx @dptr,a

jmp last

L4v: mov a,r5

subb a,#99h ; check whether i/p is greater than 3V

jc L3v ; jump if input is less than 3V

mov a,#08h ; send high signal to 4th line

movx @dptr,a

jmp last

L3v: mov a,r5

subb a,#66h ; check whether i/p is greater than 2V

jc L2v ; jump if input is less than 2V

mov a,#04h ; send high signal to 3rd line

movx @dptr,a

jmp last

L2v: mov a,r5

subb a,#33h ; check whether i/p is greater than 1V

jc L1v ; jump if input is less than 1V

mov a,#02h ; send high signal to 2nd line

movx @dptr,a

jmp last

L1v: mov a,r5

mov a,#01h ; send high signal to 1st line

movx @dptr,a

last: mov r1,#0ffh

here: djnz r1,here

mov r2,#0ffh

here1: djnz r2,here1

jmp start

.end

PROGRAM TO GENERATE STAIRCASE WAVE USING DAC





Here DAC 0808 is connected to port 1 of 8051. To check Staircase wave you can connect output to CRO.

start: mov a,#00 ;move zero to accumulator

loop: mov p1,a ;move (accumulator) to port 1

add a,#33h ;add 33 to accumulator

mov r1,#0ffh ;delay



PROGRAM TO GENERATE TRIANGLE WAVE USING DAC

mov a,#0 ;move zero to accumulator

up: mov p1,a ;move (accumulator) to port 1

inc a ;increment the (accumulator)

cjne a,#0ffh,up ;compare (accumulator) with ff

down: dec a ;decrement the (accumulator)

mov p1,a ;move (accumulator) to port 1

cjne a,#00,down ;compare (accumulator) with 0

sjmp up ;repeat again



PROGRAM TO GENERATE SINE WAVE OF 200Hz USING DAC

mov r0,#08 ;look up table is stored in internal RAM

mov @r0,#7eh

inc r0

mov @r0,#9fh

inc r0

mov @r0,#0bfh

inc r0

mov @r0,#0d9h

inc r0

mov @r0,#0feh

inc r0

mov @r0,#0fah

inc r0

mov @r0,#0ffh

inc r0

mov @r0,#0fah

inc r0

mov @r0,#0eeh

inc r0

mov @r0,#0d9h

inc r0

mov @r0,#0bfh

inc r0

mov @r0,#9fh

inc r0

mov @r0,#7eh

inc r0

mov @r0,#5eh

inc r0

mov @r0,#3fh

inc r0

mov @r0,#25h

inc r0

mov @r0,#11h

inc r0

mov @r0,#4

inc r0

mov @r0,#0

inc r0

mov @r0,#4

inc r0

mov @r0,#11h

inc r0

mov @r0,#25h

inc r0

mov @r0,#3fh

inc r0

mov @r0,#5eh

start: mov r1,#18h ;load count in r1

mov r0,#08 ;load starting address of look up table to r0

up: mov a,@r0 ;get the data from look up table

mov p1,a ;send data to port 1

inc r0 ;increment the look up table address

mov r3,#92 ;delay to get 200Hz frequency

loop: djnz r3,loop

djnz r1,up

sjmp start



delay: djnz r1,delay

cjne a,#32h,loop ;compare (acc) with 32

jmp start

PROGRAM TO FIND THE FREQUENCY OF A SQUARE WAVE





Here unknown square wave is applied to P3.4. To get the frequency you have to count the number of pulses in a second. Next display that count using 7-segment display.


org 9000h

begin: mov tcon,#00h

mov r0,#0d6h ;lsb of delay

mov r1,#22h ;msb of delay

mov tmod,#25h ;t1-mode2 timer,t0-mode1 counter

mov th1,#0a2h ;delay of .1ms

mov th0,#00h

mov tl0,#00h ;initialize counter

clr a.5

mov ie,#88h ;enable t1 overflow interrupt

mov tcon,#50h ;initiate counting

up: jb a.5,dsply

sjmp up

dsply: mov p1,tl0

mov p2,th0

lcall 66c1h ;display frequency

sjmp begin


Interrupt service routine

org 8028h

djnz r0,skip ;check whether 1sec is over by

djnz r1,skip ;decrementing R0 & R1

clr tr0 ;stop counter

clr tr1 ;stop timer

setb a.5

skip: reti

.end

PROGRAM FOR SERIAL COMMUNICATION



The 8051 has two pins that are used specifically for transferring and receiving data serially. These two pins are called TxD and RxD are the part of port 3.

TRANSMITTER PROGRAM


mov tmod,#20h ;Timer 1 mode 2

mov th1,#fdh ;9600 baud rate

mov r0,#20h

mov scon,#50h ;8-bit, 1 stop bit, REN enabled

mov r1,#05h ;5 data to transmit

clr ti ;Ready for transmitting

movx a,@r0

mov sbuf,a ;move transmitting data to sbuf

setb tr1 ;Start timer 1

here: jnb ti,here ;wait for last bit to transfer

clr ti ;get ready for next byte

inc r0

movx a,@r0

mov sbuf,a ;load the next data

djnz r1,here

lcall 03h

.end

RECEIVER PROGRAM BY POLLING METHOD


mov tmod,#20h ;Timer 1, mode 2

mov th1,#fdh ;9600 baud rate

mov r0,#20h

mov scon,#50h ;8-bit, 1 stop bit, REN enabled

clr ri ;Ready to receive

setb tr1 ;start timer

here: jnb ri,here ;wait for last bit to receive

mov a,sbuf ;move received data to a

movx @r0,a

clr ri ;get ready for next byte

inc r0

sjmp here

.end

RECEIVER PROGRAM BY INTERRUPT METHOD

mov ie,#90h

mov tmod,#20h ;Timer 1, mode 2

mov th1,#fdh ;9600 baud rate

mov dptr,#9000h

mov scon,#50h ;8-bit, 1 stop bit, REN enabled

clr ri ;ready to receive

setb tr1 ;start timer

here: sjmp here


Interrupt service routine.

mov a,sbuf ;move received data to a

movx @dptr,a

clr ri ;get ready for next byte

inc dptr

reti



TO GENERATE RECTANGLE WAVE OF 500 Hz WITH 60% DUTY CYCLE USING TIMER 1 MODE 1


mov tmod,#10h ;timer 1, mode 1

start: mov th1,#fbh ;load count - ON time

mov tl1,#aah

setb p1.0 ;set output

setb tr1 ;start timer

back: jnb tf1,back ;check overflow flag

clr tf1

clr p1.0 ;clear output

mov th1,#fdh ;load count - OFF time

mov tl1,#1eh

setb tr1 ;start timer

back1: jnb tf1,back1 ;check overflow flag

clr tf1

sjmp start


TO GENERATE SQUARE WAVE OF 500 Hz USING TIMER 1 MODE 1

mov tmod,#10h ;timer 1, mode 1

start: mov th1,#0fch ;load the count to t1

mov tl1,#68h

cpl p1.0 ;compliment output

setb tr1 ;start timer

back: jnb tf1,back ;check timer 1 overflow flag

clr tf1

sjmp start


TO GENERATE SQUARE WAVE OF 10K Hz USING TIMER 1 MODE 2

mov tmod,#20h ;timer 1,mode 2
mov th1,#210 ;load the count

setb tr1 ;start timer

back: jnb tf1,back ;check timer 1 overflow flag

cpl p1.0 ;compliment output

clr tf1

sjmp back

PROGRAM TO INTERFACE KEYBOARD USING 8255 PORTS





Here 8255 is interfaced to 8051 and that 8255 ports are used for keyboard interfacing. You can directly use 8051 ports. Here Port A is configured as input port and Port C is configured as output port.


mov a,#90h

mov dptr,#2023h ;configure 8255 ports

movx @dptr,a ;port A-i/p, port C-o/p

start: mov a,#07h

mov dptr,#2022h

movx @dptr,a ;set all rows HIGH

mov dptr,#2020h

wait: movx a,@dptr

jz wait ;wait until a key is pressed

mov r1,#00h ;number of key

mov a,#01h ;to set 1 row HIGH

nextrow: mov dptr,#2022h

mov r2,a

movx @dptr,a

mov dptr,#2020h

movx a,@dptr

jnz colscan ;scan cols. if any key is pressed in that row

mov a,r1

add a,#03h

mov r1,a ;inc key no. by 8

mov a,r2

rl a

ajmp nextrow

colscan: rrc a ;get the pressed number

jc done

inc r1

ajmp colscan

done: mov r6,r1 ;display the pressed number

lcall 66d3h

mov dptr,#2020h

loop: movx a,@dptr ;stay here until key is released

jnz loop

ajmp start

.end

PROGRAM TO GENERATE REAL TIME CLOCK USING TIMER AND INTERRUPT

org 9000h

mov tmod,#20h ;configuring timer t1,mode 2

mov th1,#01h ;load count 553us of delay

mov ie,#88h ;enable timer1 overflow interrupt

lcall 66f5h ;Input the hours and minutes from the keyboard

mov r6,31h ;minutes

mov r4,32h ;hours

mov r5,#00 ;seconds

setb tr1 ;start timer

back2: jmp back2

org 8028h ;timer interrupt routine

mov r0,#212

lcall 6798h ;Delay of 999.45ms

inc r5 ;increment second

mov a,r5

add a,#00

da a ;Decimal adjustment

mov r5,a

xrl a,#60h ;compare second is equal to 60

jz min

jmp last

min: mov r5,#00h

inc r6 ;increment minute

mov a,r6

add a,#00

da a ;Decimal adjustment

mov r6,a

xrl a,#60h ;compare minute is equal to 60

jz hr

jmp last

hr: mov r6,#00h

inc r4 ;increment hour

mov a,r4

add a,#00

da a ;Decimal adjustment

mov r4,a

xrl a,#24h ;compare hour is equal to 24

jnz last

mov r4,#00

last: push r5 ;Display the Time

push r6

push r4

mov r7,r4

lcall 66c1h ;Address field

mov r6,r5

lcall 66d3h ;Data field

pop r4

pop r6

pop r5

clr tf1

reti