Question 1(a) [3 marks]

State the features of ATmega32.

Answer:

Feature	Description
Flash Memory	32KB programmable memory
SRAM	2KB internal SRAM
EEPROM	1KB non-volatile data storage
I/O Pins	32 programmable I/O lines
Timers	3 flexible timer/counters
ADC	10-bit 8-channel ADC

Operating Voltage: 2.7V to 5.5V range
Clock Speed: Up to 16 MHz operation
Communication: USART, SPI, I2C interfaces

Mnemonic: "Fast SRAM Enjoys Input Timers And Communication"

Question 1(b) [4 marks]

Write criteria for choosing microcontroller.

Answer:

Criteria	Consideration
Processing Speed	Clock frequency requirements
Memory Size	Program and data storage needs
I/O Requirements	Number of pins needed
Power Consumption	Battery life considerations
Cost	Budget constraints
Development Tools	Compiler and debugger availability

Application Type: Real-time vs general purpose
Communication Needs: Serial, parallel, wireless protocols
Package Size: Space constraints in final product

Mnemonic: "Processing Memory I/O Power Cost Development Application Communication Package"

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[Output Devices]
    B <--> D[Memory]
    B <--> E[Communication Interface]
    F[Power Supply] --> B
    G[Clock/Timer] --> B

Block Functions:

Processor: Central processing unit executing instructions
Memory: Stores program code and data temporarily
Input Devices: Sensors, switches providing system input
Output Devices: Actuators, displays showing results
Communication: Interfaces for external device connectivity
Power Supply: Provides stable voltage to all components
Clock/Timer: Synchronizes system operations and timing

Mnemonic: "Processors Memory Input Output Communication Power Clock"

Question 1(c OR) [7 marks]

Define real time operating system and explain its characteristics.

Answer:

Real Time Operating System (RTOS): Operating system designed to process data and events within strict time constraints.

Characteristic	Description
Deterministic	Predictable response times
Preemptive	Higher priority tasks interrupt lower ones
Multitasking	Multiple tasks run concurrently
Fast Context Switch	Quick task switching capability
Priority Scheduling	Tasks executed based on priority
Interrupt Handling	Efficient interrupt processing

Hard Real-time: Missing deadline causes system failure
Soft Real-time: Missing deadline degrades performance
Time Constraints: Operations must complete within deadlines

Mnemonic: "Deterministic Preemptive Multitasking Fast Priority Interrupt"

Question 2(a) [3 marks]

Draw pin diagram of ATmega32.

Answer:

      +---U---+
PB0   |1    40| PA0
PB1   |2    39| PA1  
PB2   |3    38| PA2
PB3   |4    37| PA3
PB4   |5    36| PA4
PB5   |6    35| PA5
PB6   |7    34| PA6
PB7   |8    33| PA7
RESET |9    32| AREF
VCC   |10   31| GND
GND   |11   30| AVCC
XTAL2 |12   29| PC7
XTAL1 |13   28| PC6
PD0   |14   27| PC5
PD1   |15   26| PC4
PD2   |16   25| PC3
PD3   |17   24| PC2
PD4   |18   23| PC1
PD5   |19   22| PC0
PD6   |20   21| PD7
      +-------+

Mnemonic: "Port B A Reset Vcc Ground Crystal Port D C"

Question 2(b) [4 marks]

Explain status register of ATmega32.

Answer:

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

Status Register (SREG): Contains arithmetic operation results
Flags Update: Automatically set/cleared by ALU operations
Conditional Branching: Used for program flow control

Mnemonic: "I Think Half Sign Overflow Negative Zero Carry"

Question 2(c) [7 marks]

Explain data memory of ATmega32 in detail.

Answer:

graph TD
    A[Data Memory Space] --> B[General Purpose Registers R0-R31]
    A --> C[I/O Memory 0x20-0x5F]
    A --> D[Extended I/O 0x60-0xFF]
    A --> E[Internal SRAM 0x100-0x8FF]

Memory Organization:

General Purpose Registers: 32 registers (R0-R31) for data operations
I/O Memory: Direct access to peripheral control registers
Extended I/O: Additional peripheral registers and stack pointer
Internal SRAM: 2KB volatile memory for variables and stack
Address Space: Linear addressing from 0x00 to 0x8FF
Stack Operation: Grows downward from high memory addresses

Mnemonic: "General I/O Extended SRAM Address Stack"

Question 2(a OR) [3 marks]

Write functions of DDRx, PINx and PORTx registers.

Answer:

Register	Function
DDRx	Data Direction Register - configures pin as input/output
PINx	Pin Input Register - reads current pin state
PORTx	Port Output Register - writes data to output pins

DDRx Bit: 1 = Output, 0 = Input configuration
PINx Read: Returns actual voltage level on pins
PORTx Write: Controls output state when pin is output

Mnemonic: "Direction Input Output"

Question 2(b OR) [4 marks]

Explain different I/O registers associated with EEPROM in AVR.

Answer:

Register	Function
EEARH/EEARL	EEPROM Address Register (9-bit address)
EEDR	EEPROM Data Register
EECR	EEPROM Control Register

EECR Control Bits:

EERIE: EEPROM Ready Interrupt Enable
EEMWE: EEPROM Master Write Enable
EEWE: EEPROM Write Enable
EERE: EEPROM Read Enable

Programming Sequence: Set address → Set data → Enable master write → Enable write

Mnemonic: "Address Data Control Ready Master Write Read"

Question 2(c OR) [7 marks]

Explain different ways of connecting clock sources to the AVR.

Answer:

Clock Source	Description
External Crystal	High precision, 1-16MHz
External RC	Low cost, moderate precision
Internal RC	Built-in 1/8MHz, no external components
External Clock	External clock signal input

graph TD
    A[Crystal Oscillator] --> D[AVR Microcontroller]
    B[RC Oscillator] --> D
    C[Internal RC] --> D
    E[External Clock] --> D

Clock Configuration:

Fuse Bits: CKSEL3:0 and SUT1:0 select clock source
Startup Time: Different sources have varying startup delays
Frequency Range: Internal RC provides 1MHz or 8MHz
External Components: Crystal requires capacitors for stability

Mnemonic: "Crystal RC Internal External Fuse Startup Frequency Components"

Question 3(a) [3 marks]

Write function of registers associated with Timer 1.

Answer:

Register	Function
TCNT1H/TCNT1L	Timer/Counter 1 register (16-bit)
TCCR1A/TCCR1B	Timer/Counter 1 Control registers
ICR1H/ICR1L	Input Capture register
OCR1AH/OCR1AL	Output Compare A register
OCR1BH/OCR1BL	Output Compare B register

TIMSK: Timer Interrupt Mask register
TIFR: Timer Interrupt Flag register

Mnemonic: "Timer Control Input Output Mask Flag"

Question 3(b) [4 marks]

Discuss steps to program Timer0 in Normal mode.

Answer:

Programming Steps:

Set Timer Mode: Configure TCCR0 for Normal mode
Select Prescaler: Choose clock division ratio
Load Initial Value: Set TCNT0 register
Enable Interrupts: Set TOIE0 in TIMSK (if needed)
Start Timer: Set prescaler bits in TCCR0

TCCR0 = 0x05;    // Normal mode, prescaler 1024
TCNT0 = 0x00;    // Initial value
TIMSK |= 0x01;   // Enable overflow interrupt

Mnemonic: "Set Select Load Enable Start"

Question 3(c) [7 marks]

Write a C program to receive bytes of data serially and put them on PORT A. Set the baud rate at 9600, 8-bit, and 1 stop bit.

Answer:

#include <avr/io.h>

void USART_Init() {
    // Set baud rate to 9600 (assuming 8MHz clock)
    UBRRH = 0x00;
    UBRRL = 51;
    
    // Enable receiver
    UCSRB = (1<<RXEN);
    
    // Set frame format: 8 data bits, 1 stop bit
    UCSRC = (1<<URSEL)|(3<<UCSZ0);
}

unsigned char USART_Receive() {
    // Wait for data to be received
    while(!(UCSRA & (1<<RXC)));
    return UDR;
}

int main() {
    DDRA = 0xFF;        // PORTA as output
    USART_Init();       // Initialize USART
    
    while(1) {
        PORTA = USART_Receive();  // Receive and display
    }
    return 0;
}

Mnemonic: "Initialize Receive Display Loop"

Question 3(a OR) [3 marks]

Write function of registers associated with Serial Communication in AVR.

Answer:

Register	Function
UDR	USART Data Register
UCSRA	USART Control and Status Register A
UCSRB	USART Control and Status Register B
UCSRC	USART Control and Status Register C
UBRRH/UBRRL	USART Baud Rate Registers

Key Functions: Data transmission/reception, status monitoring, control configuration

Mnemonic: "Data Control Status Baud"

Question 3(b OR) [4 marks]

Discuss steps to program AVR to transfer data serially.

Answer:

Programming Steps:

Set Baud Rate: Configure UBRRH/UBRRL registers
Enable Transmitter: Set TXEN bit in UCSRB
Set Frame Format: Configure data bits, stop bits in UCSRC
Wait for Empty Buffer: Check UDRE flag in UCSRA
Load Data: Write data to UDR register

void USART_Transmit(unsigned char data) {
    while(!(UCSRA & (1<<UDRE)));  // Wait for empty buffer
    UDR = data;                   // Send data
}

Mnemonic: "Baud Enable Format Wait Load"

Question 3(c OR) [7 marks]

Write a C program to toggle only the PORTB.4 bit continuously every 2 ms. Use timer 1, Normal mode, and no prescaler to create the delay. Assume XTAL=8MHz.

Answer:

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

volatile unsigned int timer_count = 0;

ISR(TIMER1_OVF_vect) {
    timer_count++;
    if(timer_count >= 1) {  // Approximately 2ms
        PORTB ^= (1<<4);    // Toggle PORTB.4
        timer_count = 0;
        TCNT1 = 49911;      // Reload for 2ms delay
    }
}

int main() {
    DDRB |= (1<<4);         // PORTB.4 as output
    
    // Timer1 Normal mode, no prescaler
    TCCR1A = 0x00;
    TCCR1B = 0x01;          // No prescaler
    
    TCNT1 = 49911;          // Initial value for 2ms
    TIMSK |= (1<<TOIE1);    // Enable Timer1 overflow interrupt
    
    sei();                  // Enable global interrupts
    
    while(1) {
        // Main loop
    }
    return 0;
}

Calculation: For 2ms delay with 8MHz clock: 8MHz × 2ms = 16000 cycles Timer1 counts: 65536 - 16000 = 49536 (approximately 49911 for adjustment)

Mnemonic: "Configure Timer Calculate Enable Loop"

Question 4(a) [3 marks]

Draw interfacing diagram of ULN2803 with ATmega32.

Answer:

ATmega32          ULN2803          Load
+---------+      +--------+      +------+
|   PB0   |----->|   1    |----->| Relay|
|   PB1   |----->|   2    |----->| LED  |
|   PB2   |----->|   3    |----->| Motor|
|   PB3   |----->|   4    |      +------+
|   PB4   |----->|   5    |         |
|   PB5   |----->|   6    |         |
|   PB6   |----->|   7    |         |
|   PB7   |----->|   8    |         |
|         |      |   9    |<--------+  +12V
|   GND   |----->|  10    |
+---------+      +--------+

Connection Details:

Input: ATmega32 PORTB pins to ULN2803 inputs
Output: ULN2803 outputs drive high current loads
Common: Pin 9 connects to positive supply, Pin 10 to ground

Mnemonic: "Input Output Common Supply Ground"

Question 4(b) [4 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;    // PORTB as input
    DDRC = 0xFF;    // PORTC as output
    PORTB = 0xFF;   // Enable pull-up resistors on PORTB
    
    unsigned char data;
    
    while(1) {
        data = PINB;     // Read data from PORTB
        PORTC = data;    // Send data to PORTC
    }
    
    return 0;
}

Program Flow:

Configure Ports: Set direction registers
Enable Pull-ups: Activate internal pull-up resistors
Read Data: Get byte from PINB register
Write Data: Output byte to PORTC register

Mnemonic: "Configure Enable Read Write"

Question 4(c) [7 marks]

Draw and explain interfacing of MAX7221 with ATmega32.

Answer:

ATmega32              MAX7221           7-Segment Display
+---------+          +---------+        +-------------+
|   PB5   |--------->|   DIN   |        |     a       |
|   PB7   |--------->|   CLK   |        |   f   b     |
|   PB4   |--------->|   LOAD  |        |     g       |
|   VCC   |--------->|   VCC   |        |   e   c     |
|   GND   |--------->|   GND   |        |     d   dp  |
+---------+          |  DIG0-7 |------->+-------------+
                     | SEG A-G |
                     |   DP    |
                     +---------+

Interface Description:

SPI Communication: Uses 3-wire SPI protocol
DIN (Data In): Serial data input from PB5 (MOSI)
CLK (Clock): Clock signal from PB7 (SCK)
LOAD (Chip Select): Latch signal from PB4 (SS)
Multiplexed Display: Controls up to 8 seven-segment digits
Current Control: Internal current limiting for LEDs

Programming Steps: Initialize SPI → Send address → Send data → Toggle LOAD pin

Mnemonic: "SPI Data Clock Load Multiplex Current Program"

Question 4(a OR) [3 marks]

Draw interfacing diagram of LM35 with ATmega32.

Answer:

LM35 Temperature Sensor    ATmega32
+-------------------+     +-----------+
|        VCC        |---->|    VCC    |
|                   |     |           |
|       OUT         |---->|   PA0     | (ADC0)
|                   |     |           |
|       GND         |---->|   GND     |
+-------------------+     +-----------+

Connection Details:

VCC: Connect to +5V supply
OUT: Analog output to ADC channel (PA0)
GND: Connect to ground
Output: 10mV/°C linear voltage output

Mnemonic: "VCC OUT GND Linear"

Question 4(b OR) [4 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;        // PORTB as output
    PORTC |= (1<<5);    // Enable pull-up on PC5
    
    while(1) {
        if(PINC & (1<<5)) {     // Check if bit 5 is HIGH
            PORTB = 0x55;       // Send 55H to PORTB
        }
        else {
            PORTB = 0xAA;       // Send AAH to PORTB
        }
    }
    
    return 0;
}

Program Logic:

Monitor Bit: Check PC5 status using bit masking
Conditional Output: Send different values based on input
Continuous Loop: Monitor continuously for changes

Mnemonic: "Monitor Conditional Output Loop"

Question 4(c OR) [7 marks]

Discuss registers used to program SPI in the AVR.

Answer:

Register	Function
SPCR	SPI Control Register
SPSR	SPI Status Register
SPDR	SPI Data Register

SPCR Control Bits:

SPIE: SPI Interrupt Enable
SPE: SPI Enable
DORD: Data Order (MSB/LSB first)
MSTR: Master/Slave Select
CPOL: Clock Polarity
CPHA: Clock Phase
SPR1:0: SPI Clock Rate Select

SPSR Status Bits:

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

Programming Sequence: Configure SPCR → Enable SPI → Write SPDR → Wait for SPIF → Read SPDR

Mnemonic: "Control Status Data Configure Enable Write Wait Read"

Question 5(a) [3 marks]

Draw pin diagram of L293D motor driver IC.

Answer:

    L293D
   +--U--+
EN1|1  16|VCC
1A |2  15|4A
1Y |3  14|4Y
GND|4  13|GND
GND|5  12|GND
2Y |6  11|3Y
2A |7  10|3A
VCC|8   9|EN2
   +-----+

Pin Functions:

EN1, EN2: Enable pins for motor control
1A, 2A, 3A, 4A: Input pins from microcontroller
1Y, 2Y, 3Y, 4Y: Output pins to motors
VCC: Logic and motor supply voltages
GND: Ground connections

Mnemonic: "Enable Input Output Supply Ground"

Question 5(b) [4 marks]

Draw and explain ADMUX register.

Answer:

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

Bit Functions:

REFS1:0: Reference Selection (00=AREF, 01=AVCC, 11=Internal 2.56V)
ADLAR: ADC Left Adjust Result (data format)
MUX4:0: Analog Channel Selection (32 possible channels)

Channel Selection Examples:

00000: ADC0 (PA0)
00001: ADC1 (PA1)
00111: ADC7 (PA7)

Mnemonic: "Reference Adjust Multiplex Channel"

Question 5(c) [7 marks]

Explain the block diagram of GSM based security system.

Answer:

graph LR
    A[Sensors] --> B[Microcontroller]
    B --> C[GSM Module]
    C --> D[Mobile Network]
    D --> E[User Mobile]
    B --> F[Alarm System]
    B --> G[Display Unit]
    H[Power Supply] --> B
    H --> C

System Components:

Sensors: PIR, door/window sensors detect intrusion
Microcontroller: Processes sensor data and controls system
GSM Module: Sends SMS/calls to registered numbers
Mobile Network: Connects to cellular infrastructure
Alarm System: Local audio/visual alerts
Display Unit: Shows system status and messages
Power Supply: Battery backup for continuous operation

Operation Flow: Sensor detects → Microcontroller processes → GSM sends alert → User receives notification → Alarm activates

Mnemonic: "Sensors Microcontroller GSM Mobile Alarm Display Power Operation"

Question 5(a OR) [3 marks]

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

Answer:

ATmega32      L293D        DC Motor
+---------+  +------+     +-------+
|   PB0   |->|EN1   |     |   M   |
|   PB1   |->|1A    |     |   O   |
|   PB2   |->|2A  1Y|---->|   T   |
|         |  |    2Y|---->|   O   |
|   VCC   |->|VCC   |     |   R   |
|   GND   |->|GND   |     +-------+
+---------+  +------+

Connections:

PB0 → EN1: Enable motor operation
PB1 → 1A, PB2 → 2A: Direction control inputs
1Y, 2Y → Motor: Output to motor terminals
VCC, GND: Power supply connections

Motor Control: Different input combinations on 1A, 2A control motor direction and speed

Mnemonic: "Enable Direction Output Power Control"

Question 5(b OR) [4 marks]

Draw and explain ADCSRA register.

Answer:

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

Bit Functions:

ADEN: ADC Enable
ADSC: ADC Start Conversion
ADATE: ADC Auto Trigger Enable
ADIF: ADC Interrupt Flag
ADIE: ADC Interrupt Enable
ADPS2:0: ADC Prescaler Select (division factor)

Prescaler Settings: 000=2, 001=2, 010=4, 011=8, 100=16, 101=32, 110=64, 111=128

Programming: Set ADEN → Configure prescaler → Set ADSC → Wait for ADIF

Mnemonic: "Enable Start Auto Interrupt Prescaler Configure"

Question 5(c OR) [7 marks]

Explain the block diagram of 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[LCD Display]
    E --> G[Data Logger]
    E --> H[Wireless Module]
    H --> I[Remote Monitoring]
    J[Power Supply] --> E
    E --> K[Alarm System]

System Components:

Temperature Sensor: Measures ambient temperature (LM35/DS18B20)
Humidity Sensor: Monitors moisture content (DHT22)
Pressure Sensor: Detects atmospheric pressure changes
Rain Sensor: Detects precipitation levels
Microcontroller: Central processing unit for data collection
LCD Display: Local visual data presentation
Data Logger: Stores historical weather data
Wireless Module: Transmits data to remote locations
Alarm System: Alerts for extreme weather conditions

Operation: Sensors collect data → Microcontroller processes → Display updates → Data logging → Wireless transmission → Alert generation

Mnemonic: "Temperature Humidity Pressure Rain Microcontroller Display Logger Wireless Alarm Operation"