Microprocessor based system design

1. UNIT - V
MICROPROCESSOR BASED SYSTEM
DESIGN, DIGITAL INTERFACING
Prepared By,
R-THANDAIAH PRABU M.E.,
Lecturer - ECE
thandaiah@gmail.com

2. Interfacing Output Peripherals
• Commonly used output peripherals in embedded systems are
– LEDs, seven-segment LEDs, and LCDs; the simplest is LED
• Two ways of connecting LEDs to I/O ports:
– LED cathodes are grounded and logic 1 from the I/O port turns on the
LEDs - The current is supplied by the I/O port called current sourcing.
– LED anodes are connected to the power supply and logic 0 from the I/O
port turns on the LEDs - The current is received by the chip called current
sinking.
Common Cathode Common Anode
Active high Active low

3. Interfacing Seven-Segment
LEDs as an Output
• Seven-segment LEDs
– Often used to display BCD numbers (1 through 9) and
a few alphabets
– A group of eight LEDs physically mounted in the shape of
the number eight plus a decimal point
– Each LED is called a segment and labeled as ‘a’ through
‘g’.

4. Interfacing Seven-Segment
LEDs as an Output
• Two types of seven-segment
LEDs
– Common anode
– Common cathode
decimal point

5. Interfacing Seven-Segment
LEDs as an Output
• In a common anode seven-
segment LED
– All anodes are connected
together to a power supply and
cathodes are connected to data
lines
• Logic 0 turns on a segment.
• Example: To display digit 1, all
segments except b and c should
be off.
• Byte 11111001 = F9H will display
digit 1.

6. BCD pgfedcba he
7_seg x
0000 001111 11 3f
0001 00110000 30
0010 0101101 1 5b
0011 010011 11 4f
0100 011001 10 66
0101 01101101 6d
0110 01111101 7d
0111 00000111 07
1000 01111111 7f
1001 01101111 6f
a a a a a a a a
f b f b b f b f f b f b f b
g g g g g g g
e c e e c c c e c c e c c
d d d d d d d
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7. Interfacing Seven-Segment
LEDs as an Output
• In a common cathode seven-
segment LED
– All cathodes are connected
together to ground and the
anodes are connected to data
lines
• Logic 1 turns on a segment.
• Example: To display digit 1, all
segments except b and c should
be off.
• Byte 00000110 = 06H will display
digit 1.

9. Seven-Segment Chips
ALPHA/NUMERIC C/A
DISPLAY

10. Interfacing to Multiple 7-Segments

11. Following is a list of semiconductor materials and the corresponding colors:
• Aluminium gallium arsenide (AlGaAs) — red and infrared
• Aluminium gallium phosphide (AlGaP) — green
• Aluminium gallium indium phosphide (AlGaInP) — high-brightness orange-red,
orange, yellow, and green
• Gallium arsenide phosphide (GaAsP) — red, orange-red, orange, and yellow
• Gallium phosphide (GaP) — red, yellow and green
• Gallium nitride (GaN) — green, pure green (or emerald green), and blue also
white (if it has an AlGaN Quantum Barrier)
• Indium gallium nitride (InGaN) — 450 nm - 470 nm — near ultraviolet,
bluishgreen and blue
• Silicon carbide (SiC) as substrate — blue
• Silicon (Si) as substrate — blue (under development)
• Sapphire (Al2O3) as substrate — blue
• Zinc selenide (ZnSe) — blue
• Diamond (C) — ultraviolet
• Aluminium nitride (AlN), aluminium gallium nitride (AlGaN), aluminium
gallium indium nitride (AlGaInN) — near to far ultraviolet (down to 210 nm)
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12. Typical LED Characteristics

13. LED Displays

14. Interfacing Dip Switches and
Interfacing LEDs

15. Interfacing Push-Button Keys

16. Key Debouncing Circuits

17. Interfacing To Alphanumeric
Displays
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18. LCD Display Characteristics
• Numeric, text and/or graphic displays
• Extremely low power
• Passive
• Temperature sensitive
• Complex drivers required to create
segment waveforms

19. LCD Technology
• Natural state
– Molecules are arranged in a loosely ordered fashion
with their long axes parallel.
• Aligned state
– When coming into contact with a finely grooved surface
(alignment layer), molecules line up in parallel along
the grooves.

20. LCD Technology
• When liquid crystals are sandwiched between upper and
lower plates, they line up with grooves pointing in
directions 'a' and 'b,' respectively. The molecules along
the upper plate point in direction 'a' and those along the
lower plate in direction 'b,' thus forcing the liquid
crystals into a twisted structural arrangement. (figure
shows a 90-degree twist) (TN type liquid crystal)

21. LCD Technology
• Light passes through liquid
crystals, following the
direction in which the
molecules are arranged. When
the molecule arrangement is
twisted 90 degrees as shown in
the figure, the light also twists
90 degrees as it passes
through the liquid crystals.

22. LCD Technology
• The molecules in liquid
crystals are easily
rearranged by applying
voltage or another
external force. When
voltage is applied,
molecules rearrange
themselves vertically
(along the electric field)
and light passes straight
through.

23. LCD Technology
• Light passes when
two polarizing filters
are arranged with
their axes aligned
(left).
• Light is blocked when
two polarizing filters
are arranged with
their axes
perpendicular (right).

24. LCD Technology
• A combination
of polarizing
filters and
twisted liquid
crystal is used to
create a liquid
crystal display.

25. LCD Character Modules
• Based on Hitachi LCD-II controller protocol
– 1 to 4 lines, 8-20 characters per line
– 4 or 8 bit parallel interface
– control signals
– Controllable cursor
– 2 read/write registers
• Instruction/status
• data

26. LCD Interfacing
• Liquid Crystal Displays (LCDs)
• cheap and easy way to display text
• Various configurations (1 line by 20 X char upto 8 lines
X 80 ).
• Integrated controller
• The display has two register
– command register
– data register
• By RS you can select register
• Data lines (DB7-DB0) used to transfer data and
commands

27. Alpha numeric LCD Interfacing
Microcontrolle
r
• Pin out E communications
bus
– 8 data pins D7:D0 R/W
– RS: Data or Command RS
Register Select DB7–DB0
– R/W: Read or Write
8
– E: Enable (Latch data) LCD
controller
• RS – Register Select LCD Module
– RS = 0 → Command Register
– RS = 1 → Data Register
• R/W = 0 → Write , R/W = 1 → Read
• E – Enable
– Used to latch the data present on the data pins.
• D0 – D7
– Bi-directional data/command pins.
– Alphanumeric characters are sent in ASCII format.

28. LCD Commands
• The LCD’s internal controller can accept several
commands and modify the display accordingly. These
commands would be things like:
– Clear screen
– Return home
– Decrement/Increment cursor
• After writing to the LCD, it takes some time for it to
complete its internal operations. During this time, it
will not accept any new commands or data.
– We need to insert time delay between any two commands or
data sent to LCD

29. Pin Description

30. Command Codes

31. Interfacing LCD with 8051
8051
LM015
P3.4
RW
P3.5 E
P3.3 RS
P1.7-P1.0 D7-D0

32. Interfacing LCD
• Hardware
– 20 x 2-line LCD displays (two lines
with 20 characters per line)
– LCD has a display Data RAM
(registers) that stores data in 8-bit
character code.
– Each register in Data RAM has its own
address that corresponds to its position
on the line. PICDEMO
• The address range for Line 1 is 00 to
13H and Line 2 is 40H to 53H.

33. Interfacing LCD
• Driver HD77480
– Three control signals:
• RS – Register Select (RA3)
• R/W – Read/Write (RA2)
• E – Enable (RA1)
– Three power connections
• Power, ground, and the variable register to control the
brightness

34. Interfacing LCD
• Can be interfaced either in the 8-bit mode or the 4-bit
mode
– In the 8-bit mode, all eight data lines are connected for data
transfer
– In the 4-bit mode, only four data lines (DB7-DB4 or DB3-
DB0) are connected and two transfers per character (or
instruction) are needed
• Driver (HD77480) has two 8-bit internal registers
– Instruction Register (IR) to write instructions to set up LCD
– Data Register (DR) to write data (ASCII characters)
IR REGISTER
DR REGISTER

35. Interfacing LCD
• LCD Operation
– When the MPU writes an instruction to IR or data to DR,
the controller:
• Sets the data line DB7 high as a flag indicating that the
controller is busy completing the operation
• Sets the data line DB7 low after the completion of the
operation
– The MPU should always check whether DB7 is low before
sending an instruction or a data byte
– After the power up, DB7 cannot be checked for the first two
initialization instructions.

36. LCD Interfacing
• Simple parallel interface – similar to LED:
VDD 7-segment
LCD
Driver/Decoder Separate Front Planes
8051 a
b
c
A d
port B e
pins C f
D g
Common Back Plane
60 Hz
Oscillator

37. TEMPERATURE CONTROLLER
USING 8085 MICROPROCESSOR
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38. AIM:
• The aim of the project is to control/maintain temperature of a plant
within a desired limit.
PROJECT DESCRIPTION:
• Industrial and control application/may require automation of the
process such as temperature, pressure, liquid flow, etc., in order to
minimize manual intervention. To automate any application an
intelligent processor plays a major role. One such processor proposed
for the project is 8085, an 8-bit microprocessor.
• The temperature controller can be used to control the temperature of
any plant. Typically it contains a Processor unit, Temperature input
unit and Control output unit. The 8085 based motherboard forms the
processing unit. The Analog-to-Digital unit together with temperature
sensor forms the temperature input unit. The relay driver forms the
control output unit. Electric power to the heating element (coil) is
supplied through relay contacts. The switching ON/OFF of the relay
controls the heat supplied to the plant.
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39. Tem p C o n tro l
M PU P la n t
In p u t o u tp u t
S im p le s c h e m a tic o f te m p e ra tu re c o n tro lle r
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40. • Operationally, the system requires two set points-upper and lower, to be
entered by the user. Whenever the temperature of the plant exceeds the
upper limit or recede the lower limit relay is turned-off, so that a
temperature is maintained within limits. The software for the
temperature controller is developed in 8085 assembly language
programs.
HARDWARE DESCRIPTION:
• The hardware consists of 8085 microprocessor motherboard, ADC
interface board, and relay and driver unit.
Block Diagram of 8085 Microprocessor based Temperature Controller
• The motherboard consists of 8085 MPU, 8KB EPROM, 8KB RAM
keyboard and display controller 8279, programmable peripheral
interface 8255, 21 key hex-keypad and six numbers of seven segment
LED’s. Ports Expansion connector parallel port connectors are
provided for external interfacing.
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41. d riv e r +V
2 6 p in c o n n e c to r
P a ra lle l p o rt
8255 8085 LATCH
PPI CPU
AD TEM PERATU
590 SEN SO R
5 0 p in E x p a n s io n c o n n e c to r
15
NC
7
A 8-A
D 0- D
ADC
P SY STEM BU S
IN T E R FA C E
BOARD
EPROM RAM 8279
8K B 8K B KEYBOARD
D IS P L A Y
D IS P L A Y
C D E F in t
8 9 A B
4 5 6 7 N xt
0 1 2 3 Sub
KEYBOARD
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42. • The temperature input board or ADC interface board consists of
ADC 0809, which is an 8-bit converter with eight channels of
input. It is interfaced with the motherboard through 50-pin bus
expansion connector. The temperature sensor ADC590 is used
to sense the temperature of the plant and its analog output is
applied to the channel-0 of ADC.
• Relay is switched ON/OFF by driving the transistor to
saturation/cut-off which is connected to port A of 8255.
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43. Temperature measurement
the most frequently measured value in industry
Protection and
head assembly
Extension Assemblies
Thermowell

44. Temperature measurement
Thermistance (RTD - resistance temperature detector):
metal whose resistance depends on temperature:
+ cheap, robust, high temperature range ( -180ºC ..600ºC),
- require current source, non-linear.
Thermistor (NTC - negative temperature coefficient):
semiconductor whose resistance depends on temperature:
+ very cheap, sensible,
- low temperature, imprecise, needs current source, strongly non-linear, fragile,
self-heating
Thermo-element (Thermoelement, thermocouple):
pair of dissimilar metals that generate a voltage proportional to the
temperature difference between warm and cold junction (Seebeck effect)
+ high precision, high temperature, punctual measurement
- low voltage, requires cold junction compensation, high amplification, linearization
Spectrometer:
measures infrared radiation by photo-sensitive semiconductors
+ highest temperature, measures surfaces, no contact
- highest price
Bimetal (Bimetall, bilame):
mechanical (yes/no) temperature indicator using the difference in the dilatation
coefficients of two metals, very cheap, widely used (toasters...)

45. Cold junction box

46. SHAFT ENCODERS
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47. • The optical motor shaft encoders are
used to get the information about the
position, direction of rotation, and speed
of rotation of various motor shafts.
• Provide digital information
• 2 types:
• Absolute and Incremental
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48. Shaft Encoder Attaching
Adjustable screw Mechanism
onnected to the platform
Shaft Encoder
Opto-swtich

49. Encoder Wheel
48 Segment Wheel Encoder Wheel with more Segments
Alternating slots make reflecting and non-reflecting surfaces.
More stripes give greater resolution to measurements.
The stripes cannot be narrow than the field of view of the slotted
optical switch.

50. Shaft Encoder Design

51. Wheel Shaft encoder connected to
the DC motor

52. Designed Shaft Encoder

53. Absolute Optical Encoders
• Used when loss of reference is not possible.
• Gray codes: only one bit changes at a time ( less uncertainty).
• The information is transferred in parallel form (many wires are necessary).
Binar Gray
y Code
000
000
001
011
001
010
010 110
111
011 101
100
53 100

54. Incremental Optical Encoders
• Relative position
light
sensor
decode
light circuitry
grating emitter
54

55. Incremental Optical Encoders
• Incremental Encoder:
light
sensor
Decode
light emitter circuitry
grating
• It generates pulses proportional to the rotation speed of the
shaft.
• Direction can also be indicated with a two phase encoder:
A
B A leads B
55

56. INCREMENTEL ENCODER
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57. Other Odometry Sensors
• Resolver
It has two stator windings
positioned at 90 degrees.
The output voltage is
proportional to the sine or
cosine function of the
rotor's angle. The rotor is
made up of a third winding,
winding C
Potentiometer
= varying
resistance
57

58. ROBOT
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59. Embedded Control
• Microcontrollers are placed in devices, or
embedded, for operation and control.

60. What is a Robot?
• A robot is a machine that gathers information
about its environment (senses) and uses that
information (thinks) to follow instructions to
do work (acts)
– The “sensing” part provides input to the robot
through switches, light sensors,
– The thinking part is the microcontroller brain
– The acting part could be through lights, motors,
actuators, sounds, etc

61. Robots and Applications
• Robots come in many shapes and sizes
1. Ka
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speed e 100 manoid rob
weldin i o
3. MI
NI-RO g and precision, h t
BOT R cutting igh-
Sandi ESEA robot
4. Mi a Nati RCH —
ni-rob onal L
abora
the blo ot that can tories
odstre travel
am throug
h

62. High-Tech and Aerospace use
Ecological Undersea Research JP Aerospace
Data Collection Harbor Branch Test Launch
EME Systems Institute