MICROCONTROLLER & EMBEDDED SYSTEM LAB (EC-606) - Important Questions

Explain the operation of microcontroller timers/counters. Derive the expression for the timer overflow period for an $n$-bit timer with prescaler $N$, programmable top value $\text{TOP}$, and clock frequency $f_{clk}$. Show how this expression reduces for an 8-bit timer with $\text{TOP}=255$.

Design a timer-based delay of $1\,\text{ms}$ using a microcontroller with $f_{clk}=16\,\text{MHz}$ and a 16-bit timer that supports prescaler values $\left\{1,8,64,256,1024\right\}$. Calculate the required prescaler and the initial timer count (assume timer counts up to $\text{TOP}=65535$) to obtain the delay in a single timer overflow. Show all steps and formulas.

Describe the different types of interrupts available in typical microcontrollers (maskable, non-maskable, external, peripheral). Explain interrupt priorities and nested interrupts. Write pseudocode to configure an external interrupt to trigger on a falling edge and handle debouncing in the ISR.

Explain the operation of UART asynchronous serial communication. Derive the formula for baud-rate generator value given oscillator frequency $f_{osc}$ and desired baud rate $Baud$. Use the common formula for an 8-bit baud-rate register in the form $\text{UBRR} = \left(\frac{f_{osc}}{16\times Baud}\right) - 1$ and explain each term. Calculate $\text{UBRR}$ for $f_{osc}=16\,\text{MHz}$ and $Baud=9600$.

Explain the working principle of a successive approximation ADC and the steps required to interface it with a microcontroller. For a 10-bit ADC with reference voltage $V_{ref}=5\,\text{V}$, calculate the digital output value for an analog input $V_{in}=2.3\,\text{V}$. Use the formula $D = \left\lfloor \frac{V_{in}}{V_{ref}} \times \left(2^{10}-1\right) \right\rfloor$ and show the numerical result.

Explain how Pulse Width Modulation (PWM) is generated using a timer. Derive the relation between the timer compare register value $\text{OCR}$, the timer top value $\text{TOP}$, and the duty cycle. Express the duty cycle as a percentage using the formula $\text{Duty(\%)} = 100\times\frac{\text{OCR}}{\left(\text{TOP}+1\right)}$. Describe how changing prescaler affects PWM frequency and resolution.

Describe the I2C protocol including START, STOP conditions, 7-bit addressing, read/write bit, and ACK/NACK mechanism. Provide the detailed bus transaction sequence required for the master to read two consecutive data bytes from a slave device with 7-bit address $0x50$ starting at internal register address $0x10$. Include all START/ACK/STOP steps and describe the role of repeated START.

Explain SPI serial communication including the roles of MOSI, MISO, SCLK, and SS lines. Define CPOL and CPHA and explain how the four SPI modes (Mode 0..3) differ in clock polarity and phase. Describe how to configure a microcontroller SPI module to communicate with an SPI EEPROM that requires Mode 0 and a maximum SCLK of $5\,\text{MHz}$.

Describe the steps and timing constraints to interface a 16x2 character LCD in 4-bit mode with a microcontroller. Provide the initialization sequence, necessary control signals ($RS,RW,EN$), and explain how to write a single ASCII character to the display.

Design a closed-loop DC motor speed control system using a microcontroller to generate PWM and a tachometer (or encoder) for speed feedback. Provide the block diagram, explain sensor interfacing and pulse-count to RPM conversion, and present a discrete-time PI control law. Use the PI formula $u\left[k\right] = K_p e\left[k\right] + K_i \sum_{i=0}^{k} e\left[i\right]$ and explain how to implement anti-windup and sampling considerations.