Embedded Systems using Microwave oven

MICROWAVE OVEN
by
BOOMIKA D
BANNARI AMMAN INSTITUTE
OF TECHNOLOGY

EMBEDDED SYSTEM
 An embedded system is a microprocessor or
microcontroller based computer hardware system
with software that is designed to perform a dedicated
function.
Example:
 Mobile phone
 Microwave oven
 GPS system

IMPORTANT SOFTWARE
❏ HOST - PC
❏ TARGET - PICSIMLAB
❏ CROSS COMPILER - MPLAB X IDE

COMPONENTS
 Microcontroller (PIC16F877A)
 Matrix keypad
 7 segment display
 Cooler fan
 Digital keyboard
 LED
 Relay
 Reset button
 Buzzer
 Heater
 LCD
 Potentiometer

LIGHT EMITTING DIODE (LED)
 Semiconductor device
 Mostly used for indication purposes
 LEDs are connected to PORTB and PORTD
 TRIS stands for Tri-State
 TRISB register is important for I/O configuration
 Logic 1 = Input (Sinking Circuit)
 Logic 0 = Output (Sourcing Circuit)

CHARACTER LIQUID CRYSTAL
DISPLAY(CLCD)
 Print all the ASCII values and few special
symbols
 16 interfacing line
 Modes
 4 bit mode
 8 bit mode

PORT D = OUTPUT
RE2(RS) = OUTPUT
RE1(E) = OUTPUT
 INSTRUCTION (RS) = 0
 DATA (RS) = 1
 READ (R/W) = 1
 WRITE (R/W) = 0

TRIGGERING METHOD
 Level Trigger - Latches
 Edge Trigger - Flip flop

MATRIX KEYPAD
 Mostly used in telephones, calculators, digital lockers, and
a variety of other applications.
COLUMNS : Input = PORTB (RB0, RB1, RB2)
ROWS : Output = PORTD (RD0 to RD3)

POLLING METHOD
 Continuously monitoring something
 Disadvantages:
 Bad response time
 Loss of event
 Bad power management

INTERRUPTS
 Disturbance or signal from the hardware device.
 Communication set up in a microprocessor or
microcontroller
❏ An internal or external device requests the MPU
to stop the processing
❏ The MPU acknowledges the request
❏ Attends to the request
❏ Goes back to processing where it was interrupted
.

TIMERS
RESOLUTION (Register Width) :
 TIMER = 8 bit (0 to 255)
 TIMER = 16 bit (0 to 65535)
TICK (total tick = 255) :
 Up Count = 0 1 2 . . . . . . . . 255
 Down Count = 255 244 243 . . . . . . . . . .0
QUANTUM :
 Quantum is measure of time which is responsible for tick.
 Depending on the system clock settings
 Tick is based on instruction cycle (IC)
1 IC time = 200 n sec = quantum

SCALE AND MODES
SCALE
1:1 = tick increment after 1 IC => 200nsec
PRE SCALING
1:1 = 1 overflow go to isr => 51.2usec
POST SCALING
1:2 = after 2 overflow go to isr => 102.4usec
1:4 = after 4 overflow go to isr => 204.8usec
MODES
 Counter
 PWM or Pulse Generator
 PW or PP Measurement

Embedded Systems using Microwave oven

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