Prepare for MCU interviews with our complete 2026 guide on MCU Peripheral Interview Questions. Covering GPIO, ADC, DAC, Timers, UART, SPI, I2C, PWM, CAN, RTC, Watchdog, DMA, and more for beginners and experts.
If you are preparing for an embedded systems or MCU interview, understanding peripherals is critical. MCU peripherals form the bridge between a microcontroller and the external world, allowing it to sense, control, and communicate.
This article covers MCU Peripheral Interview Questions comprehensively, from beginner to experienced levels, making it a must-read for anyone looking to ace their interview.
What Are MCU Peripherals?
MCU peripherals are built-in hardware modules that extend the functionality of a microcontroller. These peripherals include GPIOs, ADCs, DACs, timers, UART, SPI, I2C, PWM, CAN, USB, RTC, watchdog timers, and more. They help in data acquisition, communication, timing, and control tasks. Understanding these peripherals at both conceptual and practical levels is vital for interview success.
MCU Peripheral Interview Questions and Answer
1. GPIO (General Purpose Input/Output)
GPIO pins are the simplest yet most used MCU peripherals. They allow the MCU to read switches, buttons, and sensors or control LEDs, relays, and motors.
Beginner Questions:
- What is GPIO?
- Difference between input, output, and alternate function modes.
- Explain pull-up and pull-down resistors.
- How do you configure a pin as input or output?
Intermediate Questions:
- How do you debounce a button using software?
- What are open-drain vs push-pull outputs?
- Explain how to toggle a pin using bitwise operations.
- How do you handle multiple GPIO interrupts?
Experienced Questions:
- Explain port registers: MODER, OTYPER, PUPDR, IDR, ODR in STM32.
- How would you implement a matrix keypad using GPIO?
- How to reduce power consumption when using GPIO pins?
Practical Coding Questions:
- Toggle an LED connected to a GPIO pin every 500ms using a timer.
- Read a switch and increment a counter on each press.
2. ADC (Analog-to-Digital Converter)
ADC allows MCUs to read analog signals from sensors like temperature, light, or pressure sensors.
Beginner Questions:
- What is ADC? Why is it needed?
- Explain resolution and reference voltage.
- How does sampling rate affect ADC reading?
Intermediate Questions:
- Difference between single conversion and continuous conversion mode.
- Explain oversampling and averaging techniques.
- How to read multiple channels using ADC?
Experienced Questions:
- How to implement DMA-based ADC for continuous sampling?
- Difference between SAR, Sigma-Delta, and Flash ADCs.
- Explain calibration of ADC in MCUs.
Practical Coding Questions:
- Read temperature sensor values using ADC and convert to Celsius.
- Implement a moving average filter for noisy ADC data.
3. DAC (Digital-to-Analog Converter)
DAC converts digital values into analog signals, commonly used in audio, motor control, or waveform generation.
Beginner Questions:
- What is DAC? Why is it used?
- Difference between DAC and PWM.
Intermediate Questions:
- Explain resolution and update rate.
- How to generate a sine wave using DAC?
Experienced Questions:
- How to synchronize DAC output with a timer or DMA?
- Explain voltage reference impact on DAC accuracy.
Practical Coding Questions:
- Generate a 1kHz sine wave using DAC and timer-triggered DMA.
4. Timers and Counters
Timers and counters are essential for scheduling tasks, generating PWM, measuring time intervals, and delays.
Beginner Questions:
- What is a timer? Difference between timer and counter.
- Explain one-shot, periodic, and PWM modes.
Intermediate Questions:
- Difference between input capture, output compare, and PWM mode.
- Explain prescaler and auto-reload registers.
- How to implement delays using timers instead of delay() function.
Experienced Questions:
- How to synchronize multiple timers.
- Explain dead-time insertion for complementary PWM.
- Difference between basic, general-purpose, and advanced timers in STM32.
Practical Coding Questions:
- Implement a timer interrupt to blink an LED.
- Generate a PWM signal with 50% duty cycle using timer.
5. UART (Universal Asynchronous Receiver/Transmitter)
UART is a standard peripheral for asynchronous serial communication.
Beginner Questions:
- What is UART? Difference from USART.
- Explain baud rate.
- Difference between synchronous and asynchronous communication.
Intermediate Questions:
- Difference between polling and interrupt-driven UART.
- How to implement RX/TX buffers.
- Explain parity bits, stop bits, and framing errors.
Experienced Questions:
- Implement DMA-based UART for high-speed communication.
- How to handle multiple UARTs simultaneously.
- How to detect and recover from UART overrun errors.
Practical Coding Questions:
- Send “Hello World” over UART.
- Implement an echo program using interrupt-driven UART.
6. SPI (Serial Peripheral Interface)
SPI is a fast, full-duplex communication protocol used for high-speed sensors and displays.
Beginner Questions:
- What is SPI? How many lines are used?
- Difference between master and slave.
Intermediate Questions:
- Explain MOSI, MISO, SCK, CS pins.
- Difference between full-duplex and half-duplex SPI.
- Explain SPI modes (Clock polarity and phase).
Experienced Questions:
- How to implement multi-slave SPI communication.
- Use of DMA in SPI for high-speed transfer.
- SPI data integrity: CRC or checksum implementation.
Practical Coding Questions:
- Read data from an SPI-based ADC.
- Implement SPI with interrupt for continuous data reading.
7. I2C (Inter-Integrated Circuit)
I2C is a two-wire protocol for communication with sensors, EEPROMs, and displays.
Beginner Questions:
- What is I2C? How many wires are needed?
- Difference between master and slave.
Intermediate Questions:
- Explain start, stop, ACK, and NACK signals.
- Difference between 7-bit and 10-bit addressing.
- Explain standard-mode, fast-mode, and fast-mode plus.
Experienced Questions:
- How to handle bus contention and clock stretching.
- Implement repeated start condition.
- Troubleshooting techniques for I2C bus errors.
Practical Coding Questions:
- Read/write from an I2C temperature sensor.
- Implement DMA-based I2C for continuous data transfer.
8. CAN (Controller Area Network)
CAN is widely used in automotive and industrial systems for robust communication.
Beginner Questions:
- What is CAN? Where is it used?
- Explain CAN IDs and messages.
Intermediate Questions:
- Difference between CAN 2.0A and 2.0B.
- Explain bit stuffing and error detection.
Experienced Questions:
- How to implement CAN bus with interrupt and FIFO.
- Difference between standard and extended frame.
- Handling bus-off and error passive states.
Practical Coding Questions:
- Transmit and receive CAN messages using STM32.
9. PWM (Pulse Width Modulation)
PWM is used for motor control, LED brightness, and analog signal emulation.
Beginner Questions:
- What is PWM?
- Explain duty cycle.
- Applications of PWM.
Intermediate Questions:
- How to generate PWM using timers.
- Difference between complementary and normal PWM.
Experienced Questions:
- Synchronous vs asynchronous PWM generation.
- Dead time insertion and phase-shifted PWM.
Practical Coding Questions:
- Generate variable PWM to control motor speed or LED brightness.
10. RTC (Real-Time Clock)
RTC keeps track of real-world time and is useful in low-power or time-critical applications.
Beginner Questions:
- What is RTC?
- Difference between system clock and RTC.
Intermediate Questions:
- Explain alarm, calendar, and backup registers.
- How to use RTC to wake up MCU from low-power mode.
Experienced Questions:
- How to calibrate RTC against oscillator drift.
- Using external crystal vs internal oscillator for RTC.
11. Watchdog Timer
Watchdog timers are critical for system reliability, ensuring MCU recovers from software hangs.
Beginner Questions:
- What is a watchdog timer?
- Why is it used?
Intermediate Questions:
- Difference between independent and windowed watchdog.
- How to reset MCU using watchdog.
Experienced Questions:
- How to design software to prevent watchdog reset during long operations.
- Implementing watchdog in RTOS-based systems.
12. DMA (Direct Memory Access)
DMA allows peripherals to transfer data without CPU intervention, increasing efficiency.
Beginner Questions:
- What is DMA? Why is it used?
Intermediate Questions:
- Difference between memory-to-memory, memory-to-peripheral, and peripheral-to-memory.
- How does DMA reduce CPU load?
Experienced Questions:
- Using DMA with UART, ADC, SPI for high-speed data transfer.
- Handling DMA interrupts and error flags.
13. Advanced Peripherals: USB, Ethernet, CAN-FD, Audio, LCD
USB: Device vs host, USB HID/CDC implementation, USB 2.0 vs 3.0.
Ethernet: PHY vs MAC, half-duplex vs full-duplex, implementing TCP/IP on MCU.
Audio/I2S: Generating audio signals using DAC or I2S interface.
LCD/LED Drivers: Driving displays using SPI/I2C.
Capacitive Touch: Implementing touch interfaces on MCU.
Conclusion
Preparing for MCU Peripheral Interview Questions requires a mix of conceptual knowledge, hands-on programming, and peripheral-specific expertise. From GPIO to DMA, ADC, DAC, timers, UART, SPI, I2C, CAN, PWM, RTC, watchdog, USB, and Ethernet, you need to understand register-level details, interrupts, DMA, and low-power features to stand out in interviews. Practice coding, debug peripherals, and refer to datasheets to become interview-ready. With this guide, you are now equipped to tackle beginner to advanced MCU interview questions confidently.
FAQs : MCU Peripheral Interview Questions
1. What are MCU peripherals and why are they important?
MCU peripherals are built-in hardware modules like GPIO, ADC, DAC, Timers, UART, SPI, I2C, PWM, CAN, RTC, Watchdog, and DMA. They extend a microcontroller’s capabilities, allowing it to interact with sensors, actuators, and other devices, which is critical for embedded system functionality.
2. Which MCU peripherals are most commonly asked in interviews?
Interviewers usually focus on GPIO, ADC, DAC, Timers, UART, SPI, I2C, PWM, CAN, RTC, Watchdog timers, and DMA. Understanding register-level operation, interrupts, and practical coding examples of these peripherals is highly recommended.
3. How should a beginner prepare for MCU peripheral interview questions?
Start by understanding the concept and working of each peripheral. Learn GPIO pin configuration, ADC reading, PWM generation, and UART communication. Practice coding simple examples, like blinking LEDs, reading buttons, or sending data over UART.
4. What is the difference between ADC and DAC in MCUs?
ADC (Analog-to-Digital Converter) converts analog signals into digital values so the MCU can process sensor inputs. DAC (Digital-to-Analog Converter) converts digital signals to analog outputs, useful for audio or waveform generation.
5. How do timers and counters work in MCU interviews?
Timers and counters help manage delays, generate PWM, and schedule tasks. They operate in modes like one-shot, periodic, input capture, or output compare. Understanding prescaler, auto-reload, and interrupt usage is key for interviews.
6. What is the difference between UART, SPI, and I2C?
UART is asynchronous, using TX/RX lines for serial communication. SPI is full-duplex, high-speed, with MOSI, MISO, SCK, and CS pins. I2C is a two-wire protocol (SDA/SCL) for multi-slave communication. Each has its advantages depending on speed, complexity, and distance.
7. Why are PWM signals important in MCUs?
PWM (Pulse Width Modulation) signals control motors, LEDs, and analog-like outputs using digital pins. Duty cycle adjustment allows speed control or brightness control in real-time, which is frequently asked in practical interview questions.
8. How do watchdog timers enhance system reliability?
Watchdog timers monitor software execution. If the MCU hangs or freezes, the watchdog resets it automatically, ensuring reliability in critical applications like automotive or industrial systems.
9. What is DMA and why is it useful in MCU applications?
DMA (Direct Memory Access) allows peripherals to transfer data to/from memory without CPU intervention. This improves efficiency, reduces CPU load, and is commonly tested in high-level MCU interview questions.
10. Are real-time clocks (RTC) often asked in interviews?
Yes, RTC questions are common. MCUs use RTC to track real-world time, set alarms, and wake up from low-power modes. Interviewers may ask about external vs internal oscillators and calibration techniques.
11. How can I practically demonstrate MCU peripheral knowledge in interviews?
Bring examples like LED blinking, ADC-based sensor reading, PWM motor control, UART echo programs, or SPI/I2C sensor interfacing. Writing interrupt-driven or DMA-based code showcases advanced skills.
12. How can I stay updated with MCU peripheral interview trends for 2026?
Follow MCU datasheets, embedded system blogs, online courses, and forums. Practice coding on STM32, ESP32, or Atmega platforms. Staying hands-on with GPIO, ADC, UART, SPI, I2C, PWM, CAN, and DMA will keep you ready for 2026 interviews.
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