UNIT - VMICROPROCESSOR BASED SYSTEM DESIGN, DIGITAL INTERFACING Prepared By, R-THANDAIAH PRABU M.E., Lecturer - ECE email@example.com
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
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’.
Interfacing Seven-Segment LEDs as an Output • Two types of seven-segment LEDs – Common anode – Common cathode decimal point
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.
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 af b f b b f b f f b f b f b g g g g g g ge c e e c c c e c c e c c d d d d d d d SJCET
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.
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 alsowhite (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), aluminiumgallium indium nitride (AlGaInN) — near to far ultraviolet (down to 210 nm) SJCET
LCD Display Characteristics• Numeric, text and/or graphic displays• Extremely low power• Passive• Temperature sensitive• Complex drivers required to create segment waveforms
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.
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)
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.
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.
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).
LCD Technology• A combination of polarizing filters and twisted liquid crystal is used to create a liquid crystal display.
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
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
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.
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
Interfacing LCD with 80518051 LM015 P3.4 RW P3.5 E P3.3 RSP1.7-P1.0 D7-D0
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.
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
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
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.
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
TEMPERATURE CONTROLLERUSING 8085 MICROPROCESSOR SJCET
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. SJCET
Tem p C o n tro l M PU P la n tIn 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 SJCET
• 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. SJCET
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 ADCP 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 SJCET
• 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. SJCET
Temperature measurementthe most frequently measured value in industry Protection and head assembly Extension Assemblies Thermowell
Temperature measurementThermistance (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...)
• 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 SJCET
Shaft Encoder AttachingAdjustable screw Mechanismonnected to the platform Shaft Encoder Opto-swtich
Encoder Wheel48 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.
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 10053 100
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
Other Odometry Sensors • ResolverIt has two stator windingspositioned at 90 degrees.The output voltage isproportional to the sine orcosine function of therotors angle. The rotor ismade up of a third winding,winding C Potentiometer = varying resistance 57
Embedded Control• Microcontrollers are placed in devices, or embedded, for operation and control.
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
Robots and Applications• Robots come in many shapes and sizes 1. Ka w 2. Fa adas HRP- nuc A 3P hu rcMat 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
High-Tech and Aerospace use Ecological Undersea Research JP Aerospace Data Collection Harbor Branch Test Launch EME Systems Institute