Question 1(a) [3 marks]

Draw TIFR register and write its full name.

Answer:

TIFR Register Diagram:

+----+----+----+-----+-----+----+----+----+
| 7  | 6  |  5 |  4  |  3  | 2  | 1  | 0  |
+----+----+----+-----+-----+----+----+----+
|OCF2|TOV2|ICF1|OCF1A|OCF1B|TOV1|OCF0|TOV0|
+----+----+----+-----+-----+----+----+----+

Full Name: Timer/Counter Interrupt Flag Register

TOV0: Timer0 Overflow Flag
OCF0: Timer0 Output Compare Flag
TOV1: Timer1 Overflow Flag

Mnemonic: "Timer Interrupts Flag Register"

Question 1(b) [4 marks]

Discuss data memory of ATmega32.

Answer:

Memory Type	Size	Address Range	Purpose
General Purpose Registers	32 bytes	0x00-0x1F	R0-R31 registers
I/O Memory	64 bytes	0x20-0x5F	Control registers
Internal SRAM	2048 bytes	0x60-0x85F	Variable storage

General Purpose Registers: Used for arithmetic operations and temporary storage
I/O Memory: Contains peripheral control and status registers
Internal SRAM: Used for stack, variables, and dynamic memory allocation

Mnemonic: "General I/O SRAM Memory"

Question 1(c) [7 marks]

Draw and explain general block diagram of embedded system.

Answer:

graph TD
    A[Input Devices] --> B[Processor/Microcontroller]
    B --> C[Memory]
    B --> D[Output Devices]
    B --> E[Communication Interface]
    F[Power Supply] --> B
    G[Clock Circuit] --> B

Component	Function
Processor	Controls entire system operation
Memory	Stores program and data
Input Devices	Sensors, switches, keyboards
Output Devices	LEDs, displays, motors
Communication	UART, SPI, I2C interfaces

Real-time Operation: System responds to inputs within defined time limits
Dedicated Function: Designed for specific applications
Resource Constraints: Limited memory, power, and processing capability

Mnemonic: "Processor Memory Input Output Communication"

Question 1(c OR) [7 marks]

Define real time operating system and explain its characteristics.

Answer:

Definition: Real Time Operating System (RTOS) is an operating system that guarantees response within specified time constraints for critical tasks.

Characteristic	Description
Deterministic	Predictable response times
Multitasking	Multiple tasks execution
Priority-based	High priority tasks first
Minimal Latency	Fast interrupt response

Hard Real-time: Missing deadline causes system failure
Soft Real-time: Performance degrades if deadline missed
Task Scheduling: Preemptive priority-based scheduling ensures critical tasks run first

Mnemonic: "Deterministic Multitasking Priority Minimal"

Question 2(a) [3 marks]

Write Criteria for choosing microcontroller for embedded system.

Answer:

Criteria	Importance
Processing Speed	Match application requirements
Memory Size	Sufficient ROM/RAM
I/O Pins	Adequate peripheral interfaces
Power Consumption	Battery life consideration
Cost	Budget constraints
Development Tools	Compiler, debugger availability

Mnemonic: "Speed Memory I/O Power Cost Tools"

Question 2(b) [4 marks]

Discuss Harvard Architecture in the AVR.

Answer:

Harvard Architecture Features:

Feature	Description
Separate Buses	Program and data have independent buses
Simultaneous Access	Can fetch instruction and access data simultaneously
Different Memory Types	Flash for program, SRAM for data

graph LR
    A[CPU] --> B[Program Memory Bus]
    A --> C[Data Memory Bus]
    B --> D[Flash Memory]
    C --> E[SRAM]

Advantage: Higher performance due to parallel access
16-bit Instructions: Most instructions execute in single clock cycle

Mnemonic: "Separate Simultaneous Different Performance"

Question 2(c) [7 marks]

Discuss different ways of connecting clock sources to the AVR.

Answer:

Clock Source	Frequency Range	Application
External Crystal	1-16 MHz	High accuracy applications
External RC	1-8 MHz	Cost-effective solution
Internal RC	1-8 MHz	Default, no external components
External Clock	Up to 16 MHz	Synchronized systems

Clock Selection via Fuse Bits:

CKSEL3:0 bits determine clock source
CKDIV8 bit divides clock by 8
SUT1:0 bits set startup time

Crystal Oscillator: Most stable, requires external crystal and capacitors
RC Oscillator: Less accurate but cheaper
Internal Oscillator: Factory calibrated, temperature dependent

Mnemonic: "Crystal RC Internal External"

Question 2(a OR) [3 marks]

Write size of code ROM, SRAM and EEPROM, Number of I/O pins, ADC and Timers for ATmega32.

Answer:

Specification	ATmega32
Flash ROM	32 KB
SRAM	2 KB
EEPROM	1 KB
I/O Pins	32 pins
ADC Channels	8 channels
Timers	3 timers

Mnemonic: "32K Flash 2K SRAM 1K EEPROM 32 I/O 8 ADC 3 Timers"

Question 2(b OR) [4 marks]

Draw ATmega32 pin diagram and write function of Vcc, AVcc and Aref pin.

Answer:

Pin Functions:

Pin	Function
Vcc	Main power supply (+5V)
AVcc	Analog power supply for ADC
Aref	ADC reference voltage

        ATmega32
    +--------------+
Vcc-|1           40|-AVcc
    |              |
    |              |
    |              |
    |              |
Aref|32          20|-GND
    +--------------+

Vcc: Supplies power to digital circuits
AVcc: Separate supply for ADC to reduce noise
Aref: External reference for ADC conversion

Mnemonic: "Vcc Digital AVcc Analog Aref Reference"

Question 2(c OR) [7 marks]

Explain AVR status register in detail.

Answer:

SREG (Status Register) Bits:

Bit	Name	Function
7	I	Global Interrupt Enable
6	T	Bit Copy Storage
5	H	Half Carry Flag
4	S	Sign Flag
3	V	Overflow Flag
2	N	Negative Flag
1	Z	Zero Flag
0	C	Carry Flag

+---+---+---+---+---+---+---+---+
| I | T | H | S | V | N | Z | C |
+---+---+---+---+---+---+---+---+
  7   6   5   4   3   2   1   0

I Flag: Controls global interrupt enable/disable
Arithmetic Flags: C, Z, N, V, S, H updated after ALU operations
T Flag: Used by BLD and BST instructions for bit manipulation

Mnemonic: "I Transfer Half Sign oVerflow Negative Zero Carry"

Question 3(a) [3 marks]

Explain RESET circuit for the AVR microcontroller.

Answer:

Reset Sources:

Reset Source	Description
Power-on Reset	When power is applied
External Reset	Through RESET pin
Brown-out Reset	When voltage drops
Watchdog Reset	Watchdog timer overflow

Vcc ----[R]----+---- RESET pin
               |
               C
               |
              GND

Reset Duration: Minimum 2 clock cycles
Reset Vector: Program starts from address 0x0000

Mnemonic: "Power External Brown-out Watchdog"

Question 3(b) [4 marks]

List I/O registers associated with EEPROM. Write programming steps to write data on EEPROM.

Answer:

EEPROM Registers:

Register	Function
EEAR	EEPROM Address Register
EEDR	EEPROM Data Register
EECR	EEPROM Control Register

Programming Steps:

Wait for previous write to complete (check EEWE bit)
Set address in EEAR register
Set data in EEDR register
Set EEMWE bit in EECR
Set EEWE bit within 4 clock cycles

Mnemonic: "Wait Address Data Master-Write Enable-Write"

Question 3(c) [7 marks]

Draw and explain TCCR0 register in detail.

Answer:

TCCR0 (Timer/Counter0 Control Register):

Bit	Name	Function
7	FOC0	Force Output Compare
6,3	WGM01,WGM00	Waveform Generation Mode
5,4	COM01,COM00	Compare Output Mode
2,1,0	CS02,CS01,CS00	Clock Select

+-----+-----+-----+-----+-----+-----+-----+-----+
|FOC0 |WGM01|COM01|COM00|WGM00|CS02 |CS01 |CS00 |
+-----+-----+-----+-----+-----+-----+-----+-----+
  7     6     5     4     3     2     1     0

Clock Select Options:

000: No clock (Timer stopped)
001: clk/1 (No prescaling)
010: clk/8, 011: clk/64
100: clk/256, 101: clk/1024

Mnemonic: "Force Waveform Compare Clock Select"

Question 3(a OR) [3 marks]

List registers associated with Timer 1.

Answer:

Timer1 Registers:

Register	Function
TCCR1A	Timer1 Control Register A
TCCR1B	Timer1 Control Register B
TCNT1H/L	Timer1 Counter Register
OCR1AH/L	Output Compare Register A
OCR1BH/L	Output Compare Register B
ICR1H/L	Input Capture Register

Mnemonic: "Control Counter Output-Compare Input-Capture"

Question 3(b OR) [4 marks]

Write an AVR C program to store 'G' into location 0x005F of EEPROM.

Answer:

#include <avr/io.h>
#include <avr/eeprom.h>

void eeprom_write_byte_custom(uint16_t addr, uint8_t data)
{
    while(EECR & (1<<EEWE));  // Wait for previous write
    EEAR = addr;              // Set address
    EEDR = data;              // Set data
    EECR |= (1<<EEMWE);       // Master write enable
    EECR |= (1<<EEWE);        // Write enable
}

int main()
{
    eeprom_write_byte_custom(0x005F, 'G');
    return 0;
}

Program Steps:

Check EEWE bit for completion
Load address 0x005F into EEAR
Load 'G' (ASCII 71) into EEDR
Enable master write, then write enable

Mnemonic: "Wait Address Data Master Write"

Question 3(c OR) [7 marks]

Write a C program to toggle only the PORTB.4 bit continuously every 70 μs. Use Timer0, Normal mode, and 1:8 prescaler to create the delay. Assume XTAL = 8 MHz.

Answer:

#include <avr/io.h>

int main()
{
    DDRB |= (1<<4);           // Set PB4 as output
    TCCR0 = 0x02;             // Prescaler 1:8
    
    while(1)
    {
        TCNT0 = 186;          // Load initial value
        while(!(TIFR & (1<<TOV0))); // Wait for overflow
        TIFR |= (1<<TOV0);    // Clear flag
        PORTB ^= (1<<4);      // Toggle PB4
    }
    return 0;
}

Calculation:

Clock = 8MHz/8 = 1MHz
For 70μs: Count = 70 cycles
Initial value = 256-70 = 186

Mnemonic: "Direction Control Count Wait Clear Toggle"

Question 4(a) [3 marks]

Write an AVR C program to monitor bit 5 of port C. If it is HIGH, send 55H to Port B; otherwise, send AAH to Port B.

Answer:

#include <avr/io.h>

int main()
{
    DDRC &= ~(1<<5);          // PC5 as input
    DDRB = 0xFF;              // Port B as output
    
    while(1)
    {
        if(PINC & (1<<5))     // Check PC5
            PORTB = 0x55;     // Send 55H if HIGH
        else
            PORTB = 0xAA;     // Send AAH if LOW
    }
    return 0;
}

Program Logic:

Configure PC5 as input, Port B as output
Continuously check PC5 status
Output 0x55 or 0xAA based on input

Mnemonic: "Direction Check Output"

Question 4(b) [4 marks]

Draw and explain interfacing of LM35 with ATmega32.

Answer:

graph LR
    A[LM35] --> B[PA0/ADC0]
    B --> C[ATmega32]
    D[+5V] --> A
    E[GND] --> A

Connection Table:

LM35 Pin	ATmega32 Pin	Function
Vcc	+5V	Power supply
Output	PA0 (ADC0)	Analog voltage
GND	GND	Ground

Temperature Conversion: 10mV/°C output
ADC Resolution: 10-bit (0-1023)
Voltage Range: 0V to 5V (0°C to 500°C)

Mnemonic: "Power Output Ground Temperature"

Question 4(c) [7 marks]

Draw and explain interfacing of MAX7221 with ATmega32.

Answer:

graph LR
    A[ATmega32] --> B[MAX7221]
    A --> C[7-Segment Display]
    B --> C

Connection Table:

MAX7221 Pin	ATmega32 Pin	Function
DIN	MOSI (PB5)	Serial data input
CLK	SCK (PB7)	Serial clock
LOAD	SS (PB4)	Chip select

Features:

SPI Interface: Serial communication protocol
8-Digit Display: Controls up to 8 seven-segment displays
Built-in Decoder: BCD to seven-segment conversion
Brightness Control: 16 intensity levels

Programming Steps:

Initialize SPI in master mode
Send address and data bytes
Pulse LOAD signal to latch data

Mnemonic: "Serial Clock Load Display"

Question 4(a OR) [3 marks]

Write an AVR C program to get a byte of data from Port B, and then send it to Port C.

Answer:

#include <avr/io.h>

int main()
{
    DDRB = 0x00;              // Port B as input
    DDRC = 0xFF;              // Port C as output
    
    uint8_t data;
    
    while(1)
    {
        data = PINB;          // Read from Port B
        PORTC = data;         // Send to Port C
    }
    return 0;
}

Program Function:

Configure Port B as input, Port C as output
Continuously read from PINB and write to PORTC

Mnemonic: "Input Output Read Write"

Question 4(b OR) [4 marks]

Draw and explain interfacing of ULN2803 with ATmega32.

Answer:

graph LR
    A[ATmega32 Port] --> B[ULN2803 Input]
    B --> C[ULN2803 Output]
    C --> D[Load/Relay]
    E[Vcc] --> D

ULN2803 Features:

Feature	Description
8 Darlington Arrays	High current switching
Input Current	500μA typical
Output Current	500mA per channel
Built-in Flyback Diodes	Inductive load protection

Application: Drive relays, motors, solenoids
Voltage Drop: 1.2V typical across Darlington pair
Active Low Output: Output goes low when input is high

Mnemonic: "Darlington Current Protection Drive"

Question 4(c OR) [7 marks]

Discuss registers used to program SPI in the AVR.

Answer:

SPI Registers:

Register	Bits	Function
SPCR	SPE, DORD, MSTR, CPOL	SPI Control Register
SPSR	SPIF, WCOL, SPI2X	SPI Status Register
SPDR	-	SPI Data Register

SPCR Register Bits:

SPE: SPI Enable
DORD: Data Order (MSB/LSB first)
MSTR: Master/Slave Select
CPOL: Clock Polarity
CPHA: Clock Phase

SPSR Register Bits:

SPIF: SPI Interrupt Flag
WCOL: Write Collision Flag
SPI2X: Double Speed Mode

Programming Sequence:

Configure SPI pins as input/output
Set SPCR register for desired mode
Write data to SPDR
Wait for SPIF flag
Read received data from SPDR

Mnemonic: "Control Status Data Enable Order Master"

Question 5(a) [3 marks]

Draw and explain pin diagram of L293D motor driver IC.

Answer:

        L293D
    +-----------+
1EN-|1        16|-Vcc1
1A--|2        15|-4A
1Y--|3        14|-4Y
GND-|4        13|-GND
GND-|5        12|-GND
2Y--|6        11|-3Y
2A--|7        10|-3A
Vcc2|8         9|-2EN
    +-----------+

Pin Functions:

Pin	Function
1A, 2A	Input signals for Motor 1
3A, 4A	Input signals for Motor 2
1Y, 2Y	Output to Motor 1
3Y, 4Y	Output to Motor 2
1EN, 2EN	Enable pins for motors
Vcc1	Logic supply (+5V)
Vcc2	Motor supply (+12V)

Mnemonic: "Input Output Enable Logic Motor Supply"

Question 5(b) [4 marks]

Draw and explain ADMUX register.

Answer:

ADMUX (ADC Multiplexer Selection Register):

Bit	Name	Function
7,6	REFS1,REFS0	Reference Selection
5	ADLAR	ADC Left Adjust Result
4-0	MUX4-MUX0	Analog Channel Selection

+------+------+------+------+------+------+------+------+
|REFS1 |REFS0 |ADLAR | MUX4 | MUX3 | MUX2 | MUX1 | MUX0 |
+------+------+------+------+------+------+------+------+
   7      6      5      4      3      2      1      0

Reference Selection:

00: AREF pin
01: AVcc with external capacitor
11: Internal 2.56V reference

Channel Selection: MUX bits select ADC0-ADC7 channels

Mnemonic: "Reference Adjust Multiplexer Channel"

Question 5(c) [7 marks]

Explain GSM based security system.

Answer:

graph LR
    A[Sensors] --> B[Microcontroller]
    B --> C[GSM Module]
    C --> D[Mobile Network]
    D --> E[User Mobile]
    F[Keypad] --> B
    G[Display] --> B

System Components:

Component	Function
PIR Sensor	Motion detection
Door Sensor	Entry detection
GSM Module	SMS/Call communication
Microcontroller	System control
Keypad	User interface
Display	Status indication

Working Principle:

Sensors detect intrusion
Microcontroller processes signal
GSM module sends SMS alert
User receives notification
System can be armed/disarmed remotely

Features:

Remote Monitoring: SMS notifications
Multiple Sensors: PIR, door, window sensors
User Interface: LCD display and keypad
Emergency Response: Automatic alert system

Mnemonic: "Sensors Process Communicate Alert Control"

Question 5(a OR) [3 marks]

Draw circuit diagram to interface DC motor with ATmega32 using L293D motor driver.

Answer:

ATmega32          L293D           DC Motor
    |               |               |
PA0 -----------> 1A(2)         1Y(3) -----> Motor +
PA1 -----------> 2A(7)         2Y(6) -----> Motor -
PA2 -----------> 1EN(1)
    |               |
   GND ----------> GND(4,5,12,13)
   +5V ----------> Vcc1(16)
   +12V ---------> Vcc2(8)

Connection Table:

ATmega32	L293D	Function
PA0	1A (Pin 2)	Direction control 1
PA1	2A (Pin 7)	Direction control 2
PA2	1EN (Pin 1)	Motor enable

Motor Control:

PA0=1, PA1=0: Clockwise rotation
PA0=0, PA1=1: Counter-clockwise rotation
PA2=0: Motor stop

Mnemonic: "Direction Enable Control Stop"

Question 5(b OR) [4 marks]

Draw and explain ADCSRA register.

Answer:

ADCSRA (ADC Control and Status Register A):

Bit	Name	Function
7	ADEN	ADC Enable
6	ADSC	ADC Start Conversion
5	ADATE	ADC Auto Trigger Enable
4	ADIF	ADC Interrupt Flag
3	ADIE	ADC Interrupt Enable
2-0	ADPS2-ADPS0	ADC Prescaler Select

+-----+-----+-----+-----+-----+-----+-----+-----+
|ADEN |ADSC |ADATE|ADIF |ADIE |ADPS2|ADPS1|ADPS0|
+-----+-----+-----+-----+-----+-----+-----+-----+
  7     6     5     4     3     2     1     0

Prescaler Selection:

000: Division factor 2
001: Division factor 2
010: Division factor 4
011: Division factor 8

ADC Operation Steps:

Set ADEN to enable ADC
Set ADSC to start conversion
Wait for ADIF flag
Read result from ADCH:ADCL

Mnemonic: "Enable Start Auto Interrupt Prescaler"

Question 5(c OR) [7 marks]

Explain Weather monitoring system.

Answer:

graph TD
    A[Temperature Sensor] --> E[Microcontroller]
    B[Humidity Sensor] --> E
    C[Pressure Sensor] --> E
    D[Rain Sensor] --> E
    E --> F[Display]
    E --> G[Data Logger]
    E --> H[Wireless Module]
    H --> I[Remote Monitor]

System Components:

Sensor	Parameter	Interface
LM35	Temperature	Analog (ADC)
DHT11	Humidity	Digital
BMP180	Pressure	I2C
Rain Sensor	Precipitation	Digital

Features:

Multi-parameter Monitoring: Temperature, humidity, pressure, rainfall
Data Logging: Store readings in EEPROM/SD card
Real-time Display: LCD shows current readings
Wireless Communication: WiFi/GSM for remote monitoring
Alert System: Threshold-based warnings

Applications:

Agricultural monitoring
Weather forecasting
Environmental research
Smart home automation

System Benefits:

Automated Data Collection: Continuous monitoring
Remote Access: View data from anywhere
Historical Analysis: Trend identification
Early Warning: Extreme weather alerts

Mnemonic: "Temperature Humidity Pressure Rain Display Log Wireless"