Embedded System & Microcontroller Application (4351102) - Winter 2024 Solution

Question 1(a) [3 marks]

#

State the features of ATmega32.

Answer:

• High Performance: 16 MIPS at 16MHz
• Low Power: Multiple sleep modes
• Operating Voltage: 2.7V to 5.5V

Mnemonic: “ARM-TIC” (Architecture-RISC, Memory-32KB, Timers-3, I/O-32pins, Communication-3types)

Question 1(b) [4 marks]

#

Explain criteria for choosing microcontroller.

Answer:

• Application Requirements: Real-time constraints, processing needs
• Package Size: Space limitations in final product
• Peripheral Support: ADC, timers, communication interfaces

Mnemonic: “PM-IPCD” (Performance, Memory, I/O, Power, Cost, Development)

Question 1(c) [7 marks]

#

Define the Embedded System. List the Application of Small, Medium, Large Embedded System.

Answer:

Definition: Embedded system is a computer system with dedicated function within a larger mechanical or electrical system, designed to perform specific tasks with real-time constraints.

Applications Table:

graph TD
    A[Embedded System] --> B[Small Scale]
    A --> C[Medium Scale]  
    A --> D[Large Scale]
    B --> E[Calculator
Digital Watch
Remote Control]
    C --> F[Mobile Phone
Router
Printer]
    D --> G[Car ECU
Aircraft Control
Medical Equipment]

Characteristics:

• Real-time Operation: Predictable response times
• Resource Constraints: Limited memory and processing power
• Dedicated Functionality: Single-purpose design

Mnemonic: “SML-CMP” (Small-Calculator/Medium-Mobile/Large-Lifesupport)

Question 1(c) OR [7 marks]

#

Draw and explain general block diagram of embedded system.

Answer:

graph TB
    A[Input Interface] --> B[Processor/Controller]
    B --> C[Output Interface]
    B --> D[Memory
RAM/ROM/EEPROM]
    B --> E[Communication
Interface]
    F[Sensors] --> A
    C --> G[Actuators/Display]
    E --> H[External Systems]
    I[Power Supply] --> B

Block Functions:

• Input Processing: ADC, digital input conditioning
• Output Control: PWM, relay drivers, LED displays
• Power Management: Voltage regulation, power optimization

Mnemonic: “PIOMCP” (Processor, Input, Output, Memory, Communication, Power)

Question 2(a) [3 marks]

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Write a Full form of EEPROM and explain EEPROM registers.

Answer:

Full Form: Electrically Erasable Programmable Read-Only Memory

EEPROM Registers:

• EEAR: Holds 10-bit address (0-1023) for EEPROM access
• EEDR: Data register for read/write operations
• EECR: Control bits - EERE (Read Enable), EEWE (Write Enable)

Mnemonic: “AAD-CRE” (Address-EEAR, Data-EEDR, Control-EECR)

Question 2(b) [4 marks]

#

Explain reset circuits for ATmega32

Answer:

Reset Sources Table:

graph LR
    A[Power-on] --> E[Reset Vector]
    B[External Pin] --> E
    C[Brown-out] --> E
    D[Watchdog] --> E
    E --> F[Program Counter = 0x0000]

• Reset Duration: Minimum 2 clock cycles
• Reset Vector: Program execution starts from address 0x0000
• Hardware Connection: External reset requires pull-up resistor

Mnemonic: “PEBW” (Power-on, External, Brown-out, Watchdog)

Question 2(c) [7 marks]

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Define Real Time Operating System and explain its characteristics.

Answer:

Definition: Real Time Operating System (RTOS) is an operating system designed to handle real-time applications with strict timing constraints and predictable response times.

Characteristics Table:

graph TD
    A[RTOS] --> B[Hard Real-time]
    A --> C[Soft Real-time]
    B --> D[Strict Deadlines
Safety Critical]
    C --> E[Flexible Deadlines
Performance Critical]

• Task Scheduling: Round-robin, priority-based algorithms
• Inter-task Communication: Semaphores, message queues
• Memory Management: Static allocation for predictability

Mnemonic: “DPM-FPR” (Deterministic, Preemptive, Multitasking, Fast, Priority, Resource)

Question 2(a) OR [3 marks]

#

Explain AVR family.

Answer:

AVR Family Classification:

• Architecture: 8-bit RISC, Harvard architecture
• Instruction Set: 130+ instructions, single cycle execution
• Memory: Flash program memory, SRAM, EEPROM

Mnemonic: “TAX” (Tiny-basic, mega-full, Xmega-advanced)

Question 2(b) OR [4 marks]

#

Explain the use of fuse bits for selection of ATmega32 clock sources.

Answer:

Clock Source Selection:

Clock Options Table:

• Crystal Selection: Requires external crystal and capacitors
• RC Oscillator: Built-in, less accurate but convenient
• Start-up Time: Allows crystal stabilization

Mnemonic: “CRIS” (Crystal, RC, Internal, Start-up)

Question 2(c) OR [7 marks]

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Draw ATmega32 pin configuration and explain function of MISO, MOSI, SCK & AREF Pin.

Answer:

Pin Functions Table:

• SPI Communication: MOSI, MISO, SCK work together for serial data transfer
• ADC Reference: AREF provides stable voltage reference for ADC conversion
• Pin Multiplexing: These pins have alternate functions as GPIO

Mnemonic: “MMS-A” (MOSI-out, MISO-in, SCK-clock, AREF-reference)

Question 3(a) [3 marks]

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Explain Role of DDR I/O Register

Answer:

DDR (Data Direction Register) Functions:

• Port Control: Each port has corresponding DDR (DDRA, DDRB, DDRC, DDRD)
• Bit-wise Control: Individual pin direction control
• Default State: All pins input (DDR = 0x00) after reset

Code Example:

DDRA = 0xFF;  // All Port A pins as output
DDRB = 0x0F;  // PB0-PB3 output, PB4-PB7 input

Mnemonic: “DDR-IO” (Data Direction Register controls Input/Output)

Question 3(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(void)
{
    unsigned char data;
    
    // Configure Port B as input
    DDRB = 0x00;
    
    // Configure Port C as output  
    DDRC = 0xFF;
    
    while(1)
    {
        // Read data from Port B
        data = PINB;
        
        // Send data to Port C
        PORTC = data;
    }
    
    return 0;
}

Program Explanation:

• DDRB = 0x00: Sets all Port B pins as input
• DDRC = 0xFF: Sets all Port C pins as output
• PINB: Reads current state of Port B pins
• PORTC: Writes data to Port C output pins

Mnemonic: “RSTO” (Read-PINB, Set-DDR, Transfer-data, Output-PORTC)

Question 3(c) [7 marks]

#

A door sensor is connected to the port B pin 1, and an LED is connected to port C pin7. Write an AVR C program to monitor the door sensor and, when it opens, turn on the LED.

Answer:

#include <avr/io.h>

int main(void)
{
    // Configure PB1 as input (door sensor)
    DDRB &= ~(1<<1);  // Clear bit 1
    
    // Configure PC7 as output (LED)
    DDRC |= (1<<7);   // Set bit 7
    
    // Enable pull-up for PB1
    PORTB |= (1<<1);
    
    while(1)
    {
        // Check door sensor status
        if(PINB & (1<<1))
        {
            // Door closed - turn off LED
            PORTC &= ~(1<<7);
        }
        else
        {
            // Door open - turn on LED  
            PORTC |= (1<<7);
        }
    }
    
    return 0;
}

Hardware Connection:

• Door Sensor: Connected between PB1 and GND
• LED: Connected to PC7 through current limiting resistor
• Pull-up: Internal pull-up enabled for PB1

Program Logic:

• Sensor Closed: PB1 = HIGH, LED OFF
• Sensor Open: PB1 = LOW, LED ON

Mnemonic: “DCOL” (Door-sensor, Configure-pins, Open-check, LED-control)

Question 3(a) OR [3 marks]

#

Discuss Data Types in AVR C programming.

Answer:

AVR C Data Types Table:

• Memory Efficiency: Use smallest appropriate data type
• Unsigned Types: For positive values only, doubles range
• Bit Fields: Can define specific bit-width variables

Mnemonic: “CIL-FUB” (Char-8bit, Int-16bit, Long-32bit, Float-32bit, Unsigned-positive, Bit-specific)

Question 3(b) OR [4 marks]

#

Explain Serial Communication Protocol.

Answer:

Serial Communication Parameters:

sequenceDiagram
    participant TX as Transmitter
    participant RX as Receiver
    TX->>RX: Start Bit (0)
    TX->>RX: Data Bits (8)
    TX->>RX: Parity Bit (Optional)
    TX->>RX: Stop Bit(s) (1)

• Asynchronous: No clock signal, uses start/stop bits
• RS232 Standard: ±12V levels, converted to TTL levels
• Common Baud Rates: 9600, 19200, 38400, 115200

Mnemonic: “BDPS” (Baud-rate, Data-bits, Parity-check, Stop-bits)

Question 3(c) OR [7 marks]

#

Write an AVR C program to read pins 1 and 0 of Port B and issue an ASCII character to Port D according to the following table:

Answer:

#include <avr/io.h>

int main(void)
{
    unsigned char input;
    
    // Configure PB1 and PB0 as input
    DDRB &= ~((1<<1)|(1<<0));
    
    // Configure Port D as output
    DDRD = 0xFF;
    
    // Enable pull-ups for PB1 and PB0
    PORTB |= (1<<1)|(1<<0);
    
    while(1)
    {
        // Read PB1 and PB0
        input = PINB & 0x03;  // Mask other bits
        
        switch(input)
        {
            case 0x00:  // Pin1=0, Pin0=0
                PORTD = '0';  // ASCII '0' = 0x30
                break;
                
            case 0x01:  // Pin1=0, Pin0=1
                PORTD = '1';  // ASCII '1' = 0x31
                break;
                
            case 0x02:  // Pin1=1, Pin0=0
                PORTD = '2';  // ASCII '2' = 0x32
                break;
                
            case 0x03:  // Pin1=1, Pin0=1
                PORTD = '3';  // ASCII '3' = 0x33
                break;
        }
    }
    
    return 0;
}

Truth Table Implementation:

Mnemonic: “MATS” (Mask-inputs, ASCII-conversion, Truth-table, Switch-case)

Question 4(a) [3 marks]

#

Draw interfacing diagram of relay and relay driver ULN2803 with ATmega32

Answer:

Component Functions:

• ULN2803: Darlington transistor array, current amplification
• Protection Diodes: Built-in flyback diodes for inductive loads
• Relay Coil: Requires 12V, controlled by ULN2803 output

Mnemonic: “UPC” (ULN-driver, Port-control, Current-amplify)

Question 4(b) [4 marks]

#

Write steps of programming the A/D converter using polling method

Answer:

ADC Programming Steps:

Code Implementation:

// Step 1: Configure ADMUX
ADMUX = (1<<REFS0);  // AVCC reference, channel 0

// Step 2: Enable ADC with prescaler
ADCSRA = (1<<ADEN)|(1<<ADPS2)|(1<<ADPS1)|(1<<ADPS0);

// Step 3: Start conversion
ADCSRA |= (1<<ADSC);

// Step 4: Wait for completion
while(!(ADCSRA & (1<<ADIF)));

// Step 5: Read result
result = ADC;  // Combined ADCL and ADCH

Mnemonic: “CCSWR” (Configure-ADMUX, Configure-ADCSRA, Start-conversion, Wait-complete, Read-result)

Question 4(c) [7 marks]

#

Explain I2C-Two Wire Serial Interface (TWI) Protocol in detail.

Answer:

I2C Protocol Features:

sequenceDiagram
    participant M as Master
    participant S as Slave
    M->>S: Start Condition
    M->>S: Slave Address + R/W
    S->>M: ACK
    M->>S: Data Byte
    S->>M: ACK
    M->>S: Stop Condition

I2C Frame Structure:

• Start Condition: SDA goes low while SCL is high
• Address Frame: 7-bit address + R/W bit
• Data Frame: 8-bit data + ACK/NACK
• Stop Condition: SDA goes high while SCL is high

TWI Registers in ATmega32:

• Clock Stretching: Slave can hold SCL low to slow down master
• Arbitration: Prevents collisions in multi-master systems
• Pull-up Resistors: Required on both SDA and SCL lines (4.7kΩ typical)

Mnemonic: “SAD-CSA” (Start-Address-Data, Control-Status-Address)

Question 4(a) OR [3 marks]

#

Explain any one PWM mode for controlling speed of DC motor by using 8-bit timer

Answer:

Fast PWM Mode (Mode 3):

PWM Configuration:

// Configure Timer0 for Fast PWM
TCCR0 = (1<<WGM01)|(1<<WGM00)|(1<<COM01)|(1<<CS01);

// Set duty cycle (0-255)
OCR0 = 128;  // 50% duty cycle

graph LR
    A[Timer0] --> B[PWM Signal]
    B --> C[Motor Driver]
    C --> D[DC Motor]
    E[OCR0 Value] --> A

• Duty Cycle Control: OCR0 value determines motor speed
• Non-inverting Mode: High pulse width = OCR0/255
• Motor Control: Higher duty cycle = higher speed

Mnemonic: “FTO” (Fast-PWM, Timer0, OCR0-control)

Question 4(b) OR [4 marks]

#

Write steps for reading data from an SPI device

Answer:

SPI Read Steps:

Code Implementation:

// Step 1: Configure SPI as master
SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR0);

// Step 2: Select slave
PORTB &= ~(1<<SS);

// Step 3: Send dummy byte
SPDR = 0xFF;

// Step 4: Wait for complete
while(!(SPSR & (1<<SPIF)));

// Step 5: Read data
data = SPDR;

// Step 6: Deselect slave
PORTB |= (1<<SS);

SPI Timing:

• Clock Polarity: CPOL bit determines idle state
• Clock Phase: CPHA bit determines sampling edge
• Data Order: MSB first (default) or LSB first

Mnemonic: “CSWWRD” (Configure, Select, Write-dummy, Wait, Read-data, Deselect)

Question 4(c) OR [7 marks]

#

Draw and explain interfacing diagram of LM35 with ATmega32.

Answer:

LM35 Specifications:

ADC Code for Temperature Reading:

#include <avr/io.h>

unsigned int readTemperature(void)
{
    unsigned int adcValue, temperature;
    
    // Configure ADC
    ADMUX = (1<<REFS0);  // AVCC reference, PA0
    ADCSRA = (1<<ADEN)|(1<<ADPS2)|(1<<ADPS1)|(1<<ADPS0);
    
    // Start conversion
    ADCSRA |= (1<<ADSC);
    
    // Wait for completion
    while(!(ADCSRA & (1<<ADIF)));
    
    // Read ADC value
    adcValue = ADC;
    
    // Convert to temperature
    // ADC = (Vin × 1024) / Vref
    // Vin = (10mV/°C) × Temp
    temperature = (adcValue * 500) / 1024;
    
    return temperature;
}

Temperature Calculation:

• ADC Resolution: 10-bit (0-1023)
• Reference Voltage: 5V
• LM35 Output: 10mV/°C
• Formula: Temp = (ADC × 5000mV) / (1024 × 10mV/°C)

Mnemonic: “VARC” (Voltage-output, ADC-conversion, Reference-5V, Calculation-formula)

Question 5(a) [3 marks]

#

Draw Timer 0 Working Block diagram.

Answer:

graph TD
    A[System Clock] --> B[Prescaler]
    B --> C[Timer/Counter 0]
    C --> D[Compare Unit]
    C --> E[Overflow Flag]
    D --> F[OCR0]
    D --> G[PWM Output]
    H[External Clock] --> B

    style C fill:#f9f,stroke:#333,stroke-width:4px

Timer0 Components:

• Clock Sources: Internal clock or external pin
• Modes: Normal, CTC, Fast PWM, Phase Correct PWM
• Interrupt: Timer overflow and compare match

Mnemonic: “PCCO” (Prescaler, Counter, Compare, Overflow)

Question 5(b) [4 marks]

#

Draw Interfacing of MAX7221 to ATmega32.

Answer:

MAX7221 Features:

Initialization Code:

void MAX7221_init(void)
{
    // Configure SPI pins
    DDRB |= (1<<PB5)|(1<<PB7)|(1<<PB4);  // MOSI, SCK, SS as output
    
    // Initialize SPI
    SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR0);
    
    // Wake up MAX7221
    MAX7221_write(0x0C, 0x01);  // Shutdown register
    
    // Set decode mode
    MAX7221_write(0x09, 0xFF);  // BCD decode for all digits
    
    // Set intensity
    MAX7221_write(0x0A, 0x08);  // Medium brightness
    
    // Set scan limit
    MAX7221_write(0x0B, 0x07);  // Display all 8 digits
}

Mnemonic: “SCD-ISS” (SPI-interface, Current-control, Decode-mode, Initialize-setup, Scan-limit)

Question 5(c) [7 marks]

#

Explain Weather Monitoring System.

Answer:

System Block Diagram:

graph TD
    A[Temperature Sensor
LM35] --> E[ATmega32
Microcontroller]
    B[Humidity Sensor
DHT11] --> E
    C[Pressure Sensor
BMP180] --> E
    D[Light Sensor
LDR] --> E
    E --> F[LCD Display
16x2]
    E --> G[Data Logger
EEPROM]
    E --> H[Wireless Module
ESP8266]
    H --> I[Cloud Server]
    J[Power Supply
Battery/Solar] --> E

System Components:

Features and Applications:

• Real-time Monitoring: Continuous sensor data collection
• Data Logging: Historical data storage in EEPROM
• Remote Access: WiFi connectivity for cloud upload
• Power Management: Battery backup with solar charging
• Alert System: Threshold-based warnings
• Agricultural Use: Crop monitoring, irrigation control
• Home Automation: HVAC control, energy management

Software Functions:

• Sensor Reading: ADC conversion, I2C communication
• Data Processing: Calibration, filtering, averaging
• Display Update: LCD formatting, user interface
• Communication: WiFi data transmission, protocol handling
• Storage Management: EEPROM read/write, data compression

Mnemonic: “SMART-W” (Sensors, Monitoring, Alert, Remote, Temperature, Weather)

Question 5(a) OR [3 marks]

#

Draw and explain Timer/Counter Control Register 0(TCCR0)

Answer:

TCCR0 Register Bit Structure:

Bit Functions Table:

Clock Select Options:

Waveform Generation Modes:

Mnemonic: “FWC-CS” (Force, Waveform, Compare, Clock-Select)

Question 5(b) OR [4 marks]

#

Explain the function of motor driver L293D.

Answer:

L293D Motor Driver Features:

Pin Configuration:

H-Bridge Operation:

Control Functions:

• Direction Control: IN1, IN2 determine rotation direction
• Speed Control: PWM on Enable pins (EN1, EN2)
• Dual Supply: VCC1 for logic, VCC2 for motor power
• Enable Control: EN pins enable/disable motor operation

Applications:

• Robotics: Differential drive robots
• Automation: Conveyor belt control
• RC Vehicles: Motor speed and direction control

Mnemonic: “DHIE” (Dual-channel, H-bridge, Input-control, Enable-PWM)

Question 5(c) OR [7 marks]

#

Explain Automatic Juice vending machine.

Answer:

System Block Diagram:

graph TD
    A[Keypad Input] --> H[ATmega32
Controller]
    B[Coin Sensor] --> H
    C[LCD Display] --> H
    H --> D[Pump Motors]
    H --> E[Solenoid Valves]
    H --> F[Coin Return
Mechanism]
    H --> G[Level Sensors]
    I[Power Supply] --> H
    J[Juice Containers] --> D
    D --> K[Mixing Chamber]
    E --> K
    K --> L[Dispensing Unit]

System Components:

Operation Sequence:

1. Display Menu: Show available juices and prices
2. User Selection: Customer selects juice type via keypad
3. Payment Process: Coin insertion and validation
4. Level Check: Verify ingredient availability
5. Dispensing: Activate pumps and valves in sequence
6. Mixing: Control mixing ratios and time
7. Completion: Display completion message and return change

Control Algorithm:

void dispensJuice(uint8_t selection, uint16_t amount)
{
    // Check ingredient levels
    if(checkLevels(selection))
    {
        // Calculate mixing ratios
        calculateRatio(selection);
        
        // Start dispensing sequence
        activatePump(selection, amount);
        
        // Control mixing time
        startTimer(MIXING_TIME);
        
        // Complete transaction
        displayMessage("Enjoy your juice!");
    }
    else
    {
        displayMessage("Ingredient not available");
        returnCoins();
    }
}

Features:

• Multiple Flavors: Different juice combinations
• Payment System: Coin acceptance and change return
• Inventory Management: Level monitoring and alerts
• User Interface: Menu display and selection
• Safety Features: Overflow protection, emergency stop
• Maintenance Mode: Service and cleaning cycles

Applications:

• Commercial: Shopping malls, offices, schools
• Industrial: Factory cafeterias, hospitals
• Public Places: Airports, train stations

Mnemonic: “JUMPS” (Juice-selection, User-interface, Mixing-control, Payment-system, Sensors-monitoring)