1. Interfacing of 8051
UNIT 4

2. Contents Interfacing of 7 segment display, LCD and keyboard.
Interfacing of DC motor, stepper motor and relay.
Interfacing of ADC, DAC and sensors.

3. 7 segment display

6. Interfacing of 7 segment display

7. 7 segment code for CC DP G F E D C B A
NUMBER 1 2 3

8. PROGRAM 7 SEGMENT DISPLAY
To display ‘1’
MOV A,#06H
MOV P1,A
SJMP $

9. LCD Interfacing

11. Pin No:
Name
 Function 1
VSS
This pin must be connected to the ground 2
VCC
 Positive supply voltage pin (5V DC)      3
VEE
Contrast adjustment 4 RS
Register selection 5
R/W
Read or write 6 E
 Enable 7
DB0
 Data 8
DB1 9
DB2 10
DB3 11
DB4 12
DB5 13
DB6 14
DB7 15
LED+
 Back light LED+ 16
LED-
 Back light LED- 

12. 4 Decrement cursor (shift cursor to left)
1        Clear display screen
2        Return Home
4        Decrement cursor (shift cursor to left)
5        Increment cursor (shift cursor to right)
6        shift display right
7        shift display left
8        Display off, cursor off
A        Display off, cursor on
C        Display on, cursor off
E        Display on, cursor blinking
F        Display on, cursor blinking
10        Shift cursor position to left
14        Shift cursor position to right
18        Shift the entire display to the left
1C        Shift the entire display to the right
80        Force cursor to the beginning of 1st line
C0        Force cursor to the beginning of 2nd line
38        2 lines and 5 x 7 matrix

14. Interface Program
MOV A,#38H // Use 2 lines and 5x7 matrix ACALL CMND MOV A,#0FH // LCD ON, cursor ON, cursor blinking ON ACALL CMND MOV A,#01H //Clear screen ACALL CMND MOV A,#06H //Increment cursor ACALL CMND MOV A,#82H //Cursor line one , position 2 ACALL CMND MOV A,#3CH //Activate second line ACALL CMND
MOV A,#’W’ ACALL DISP MOV A,#’E’ ACALL DISP MOV A,#’L’ ACALL DISP MOV A,#’C’ ACALL DISP MOV A,#O ACALL DISP MOV A,#’M’ ACALL DISP MOV A,#’E’ ACALL DISP

15. CMND: MOV P1,A CLR P3.5 CLR P3.4 SETB P3.3 CLR P3.3 ACALL DELY RET;
DISP:MOV P1,A SETB P3.5 CLR P3.4 SETB P3.3 CLR P3.3 ACALL DELY RET;

16. DELY: MOV R0,#0FFH
HERE: DJNZ R0, HERE
RET;
Subroutine CMND sets the logic of the RS, R/W, E pins of the LCD module so that the module recognizes the input data ( given to DB0 to DB7) as a command.
Subroutine DISP sets the logic of the RS, R/W, E pins of the module so that the module recognizes the input data as a data to be displayed .

17. 8051 & dc motor interface

19. ORG 00H // initial starting address MAIN: MOV P1,# B // motor runs clockwise ACALL DELAY // calls the 1S DELAY MOV P1,# B // motor runs anti clockwise ACALL DELAY // calls the 1S DELAY SJMP MAIN // jumps to label MAIN for repeating the cycle
DELAY: MOV R4,#0FH WAIT1: MOV R3,#0FFH WAIT2: MOV R2,#0FFH WAIT3: DJNZ R2,WAIT3 DJNZ R3,WAIT2 DJNZ R4,WAIT1 RET END

20. Stepper Motor Interfacing
What is stepper motor?
Stepper motors consist of a permanent magnetic rotating shaft, called the rotor, and electromagnets on the stationary portion that surrounds the motor, called the stator.
a motor with a resolution of 5 degrees would move its rotor 5 degrees per step, thereby requiring 72 pulses (steps) to complete a full 360 degree rotation.

21. Stepper motor operation

22. At position 1, we can see that the rotor is beginning at the upper electromagnet, which is currently active (has voltage applied to it).
To move the rotor clockwise (CW), the upper electromagnet is deactivated and the right electromagnet is activated, causing the rotor to move 90 degrees CW, aligning itself with the active magnet.
This process is repeated in the same manner at the south and west electromagnets until we once again reach the starting position.

23. In the above example, we used a motor with a resolution of 90 degrees or demonstration purposes.
In reality, this would not be a very practical motor for most applications. The average stepper motor's resolution -- the amount of degrees rotated per pulse is much higher than this.
You may double the resolution of some motors by a process known as "half-stepping".

25. Instead of switching the next electromagnet in the rotation on one at a time, with half stepping you turn on both electromagnets, causing an equal attraction between, thereby doubling the resolution.
Both the top and right electromagnets are active, causing the rotor to position itself between the two active poles

29. Sequence
Polarity
Name
Description
Wave Drive, One-Phase
Consumes the least power. Only one phase is energized at a time. Assures positional accuracy regardless of any winding imbalance in the motor.
Hi-Torque, Two-Phase
Hi Torque - This sequence energizes two adjacent phases, which offers an improved torque-speed product and greater holding torque.

30. ---+ --++ --+- -++- -+-- ++-- +--- +--+
Half-Step
Half Step - Effectively doubles the stepping resolution of the motor, but the torque is not uniform for each step.  (Since we are effectively switching between Wave Drive and Hi-Torque with each step, torque alternates each step.)  This sequence reduces motor resonance which can sometimes cause a motor to stall at a particular resonant frequency.  Note that this sequence is 8 steps.

32. Stepper motor programming
org 0H stepper equ P3 main: mov stepper, #0CH acall delay mov stepper, #06H acall delay mov stepper, #03H acall delay mov stepper, #09H acall delay sjmp main
delay: mov r7,#4 wait2: mov r6,#0FFH wait1: mov r5,#0FFH wait: djnz r5,wait djnz r6,wait1 djnz r7,wait2 ret

33. Analog to Digital Converter
Commonly used ADC device – ADC804
Pin out of ADC
CS – Chip Select , active low
RD – Read Digital data from ADC, H-L edge triggered
WR -- Start conversion, L-H pulse edge triggered
INTR -- end of conversion, Goes low to indicate conversion done
Data bits -- D0-D7
 CLK IN & CLK R –  CLK IN is an input pin connected to an external clock source when an external clock is used for timing. However, ADC804 has an internal clock generator.
To use the internal clock generator of the ADC804, the CLK IN and CLK R pins are connected to a capacitor and a resistor. In that case, the  clock frequency is determined by the equation.    f = 1/1.1RC    R=10K and C=150pF f=606Hz    the conversion time is 110us. 

34. Input Voltage range of ADC
Vref/2
(Volts)
Vin
Step size (mV)
Open (2.5)
0 to 5
5/256 = 19.53
2.56
0 to 5.12
5.12/256 =20
1.28
0 to 2.56
2.56/256 = 10
0.5
0 to 1
1/256=3.90

35. Default 0-5V. Can be changed by setting different value for Vref/2 pin
Default 0-5V. Can be changed by setting different value for Vref/2 pin.    Vin=Vin(+) – Vin (-)
Range = 0 to 2x Vref/2.     for Vin = 2x Vref/2. we get 256 as a digital output on D0-D7
Step Size a Smallest change – (2 x Vref/2)/ 256 for ADC804
for eg for  step size 10mv ,digital output on D0-D7 changes by one count for every 10mv change of  the input analog voltage.

36. Algorithm
• Make CS=0 and send a low-to-high to pin WR to start the conversion. • Keep monitoring INTR – If INTR =0, the conversion is finished and we can go to the next step. – If INTR=1, keep polling until it goes low. • After INTR=0, we make CS=0 and send a high-to-low pulse to RD to get the data out of the ADC804 chip.

37. ADC Interfacing

38. ADC_IO:
mov P1, #0xff ; To configure as input
setb p3.4
clr p3.7 ;Chip select
AGAIN
setb P3.6 ;RD=1
clr P3.5 ;WR=0
setb P3.5 ;WR=1- low to high transition
WAIT:
 jb P3.4, WAIT ;wait for INTR
clr P3.6 ;RD=0 -High to low transition
mov A, P1 ;read digital o/p
sjmp AGAIN

39. DAC Interfacing

42. Iout= Iref (D7/2+D6/4+D5/8+D4/16+D3/32+D2/64+D1/128+D0/256)
Vout=Iout x R

43. Interfacing of Relay with 8051

44. Interfacing LDR with 8051