Embedded System & Microcontroller Application (4351102) - Summer 2025 Solution

Question 1(a) [3 marks]

State the features of ATmega32.

Answer:

• 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"

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Question 1(b) [4 marks]

Write criteria for choosing microcontroller.

Answer:

• 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"

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Question 1(c) [7 marks]

Draw and explain general block diagram of embedded system.

Answer:

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"

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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.

• 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"

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Question 2(a) [3 marks]

Draw pin diagram of ATmega32.

Answer:

goat

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

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Question 2(b) [4 marks]

Explain status register of ATmega32.

Answer:

• 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"

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Question 2(c) [7 marks]

Explain data memory of ATmega32 in detail.

Answer:

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"

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Question 2(a OR) [3 marks]

Write functions of DDRx, PINx and PORTx registers.

Answer:

• 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"

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Question 2(b OR) [4 marks]

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

Answer:

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"

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Question 2(c OR) [7 marks]

Explain different ways of connecting clock sources to the AVR.

Answer:

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"

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Question 3(a) [3 marks]

Write function of registers associated with Timer 1.

Answer:

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

Mnemonic: "Timer Control Input Output Mask Flag"

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Question 3(b) [4 marks]

Discuss steps to program Timer0 in Normal mode.

Answer:

Programming Steps:

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

C

Mnemonic: "Set Select Load Enable Start"

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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:

C

Mnemonic: "Initialize Receive Display Loop"

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Question 3(a OR) [3 marks]

Write function of registers associated with Serial Communication in AVR.

Answer:

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

Mnemonic: "Data Control Status Baud"

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Question 3(b OR) [4 marks]

Discuss steps to program AVR to transfer data serially.

Answer:

Programming Steps:

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

C

Mnemonic: "Baud Enable Format Wait Load"

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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:

C

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"

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Question 4(a) [3 marks]

Draw interfacing diagram of ULN2803 with ATmega32.

Answer:

goat

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"

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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:

C

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"

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Question 4(c) [7 marks]

Draw and explain interfacing of MAX7221 with ATmega32.

Answer:

goat

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"

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Question 4(a OR) [3 marks]

Draw interfacing diagram of LM35 with ATmega32.

Answer:

goat

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"

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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:

C

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"

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Question 4(c OR) [7 marks]

Discuss registers used to program SPI in the AVR.

Answer:

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"

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Question 5(a) [3 marks]

Draw pin diagram of L293D motor driver IC.

Answer:

goat

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"

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Question 5(b) [4 marks]

Draw and explain ADMUX register.

Answer:

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"

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Question 5(c) [7 marks]

Explain the block diagram of GSM based security system.

Answer:

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"

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Question 5(a OR) [3 marks]

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

Answer:

goat

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"

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Question 5(b OR) [4 marks]

Draw and explain ADCSRA register.

Answer:

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"

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Question 5(c OR) [7 marks]

Explain the block diagram of Weather monitoring system.

Answer:

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"