Unit 2: Advanced GPIO & Peripheral Control - Practice Quiz

1 Which Python library provides low-level control of Raspberry Pi GPIO pins?

2 Which GPIO Zero class is commonly used to control an LED?

3 What is the purpose of GPIO.setup() in RPi.GPIO?

4 Which RPi.GPIO function releases GPIO resources after a program finishes?

5 What is the main advantage of interrupt-driven GPIO programming?

6 Which signal change is called a rising edge?

7 What is a callback function in GPIO event handling?

8 Why is switch debouncing used with GPIO interrupts?

9 What is the main purpose of an H-bridge circuit?

10 Why is a motor driver IC used between a GPIO pin and a DC motor?

11 Which technique is commonly used to control the speed of a DC motor?

12 What can happen if both sides of an H-bridge are switched incorrectly at the same time?

13 What input signal is commonly used to set a hobby servo's position?

14 How does a stepper motor normally move?

15 What is an acceleration profile in motor control?

16 Why is gradual acceleration useful when starting a stepper motor?

17 What does DMA stand for?

18 What is a key benefit of using DMA for GPIO timing?

19 How does DMA reduce CPU workload during GPIO control?

20 Which application benefits most directly from DMA-based GPIO control?

21 A push button is physically connected to header pin 11 on a Raspberry Pi. Which RPi.GPIO configuration correctly refers to this pin by its Broadcom GPIO number?

22 An active-low relay module connected to GPIO17 turns on when its input is LOW. Which GPIO Zero declaration gives relay.on() the expected meaning?

23 An RPi.GPIO PWM output operates at kHz with a duty cycle of . What are the approximate HIGH and LOW times in each cycle?

24 A program uses several GPIO channels but must release only channel 18 before assigning it to another module. Which RPi.GPIO call is most appropriate?

25 A mechanical button generates several transitions within ms of one press. Which event configuration best prevents multiple callbacks from the same press?

26 A sensor produces HIGH pulses lasting only microseconds, while the main loop checks the pin every ms. What is the best way to detect each pulse?

27 A GPIO callback currently performs a slow network request, causing later input events to be delayed. Which redesign is most appropriate?

28 A quadrature encoder has channels A and B. When an edge occurs on channel A, how can the program determine the rotation direction?

29 A DC motor is running through an H-bridge with IN1=HIGH, IN2=LOW, and a PWM signal on the enable pin. How should its direction be reversed while keeping approximately the same speed?

30 A V motor is controlled by ideal PWM at a duty cycle of . What approximate average voltage is applied to the motor?

31 A custom H-bridge controlling an inductive DC motor causes voltage spikes when the motor is switched off. Which addition directly protects the switching transistors?

32 A motor must rapidly change from forward to reverse without damaging the H-bridge. Which control sequence is safest?

33 A servo maps to a ms pulse and to a ms pulse in a ms period. Which pulse width and duty cycle approximately command ?

34 A stepper motor must accelerate smoothly from rest to a high target speed. How should the delay between consecutive step pulses change during acceleration?

35 A stepper motor has a full-step angle and is driven using microsteps per full step. How many step pulses are required for one complete revolution?

36 A loaded stepper motor misses steps when commanded to start immediately at high speed but works correctly when started slowly. What is the best software solution?

37 A Raspberry Pi must generate a precise pulse train while simultaneously handling network traffic. Why is DMA-based GPIO control preferable to a Python timing loop?

38 A DMA waveform keeps a GPIO pin HIGH for microseconds and LOW for microseconds in each cycle. What are its frequency and duty cycle?

39 Two GPIO timing libraries attempt to use the same DMA channel, and waveform output becomes unreliable. What is the most appropriate correction?

40 A precomputed DMA waveform remains stable under heavy CPU load, but gaps appear when a continuously streamed waveform runs for several minutes. What is the most likely cause?

41 An LED is physically connected to header pin 11. The code GPIO.setmode(GPIO.BOARD); GPIO.setup(11, GPIO.OUT) controls it correctly. If the program is rewritten as LED(11) using GPIO Zero's default numbering, which pin is addressed?

42 A GPIO Zero device is created as LED(17, active_high=False, initial_value=False). What electrical levels are expected immediately after construction and after calling led.on()?

43 A Python program generates a 1 kHz PWM signal using RPi.GPIO.PWM. Under heavy CPU and I/O load, pulse widths occasionally vary. Which modification most directly addresses the timing mechanism causing this problem?

44 A program mixes direct RPi.GPIO calls with GPIO Zero devices on the same pins. It sometimes reports numbering-mode conflicts and leaves outputs active after exceptions. Which design is most robust?

45 A flow sensor can produce valid pulses only apart. An RPi.GPIO rising-edge callback is configured with bouncetime=5. What is the most important measurement consequence?

46 An edge callback parses JSON, writes to a database, and updates a display. At high event rates, edges are lost and callback latency grows. Which redesign best preserves event responsiveness?

47 A main thread reads and resets a pulse counter while an interrupt callback executes count += 1. Why can counts still be lost in CPython, despite the Global Interpreter Lock?

48 A high-speed quadrature encoder changes state faster than Python callbacks can reliably execute. Direction and position must remain correct. Which solution is most appropriate?

49 During an H-bridge direction reversal, the high-side transistor is enabled before the previously conducting low-side transistor has fully turned off. What is the principal hazard?

50 A brushed DC motor has winding resistance . It is driven from 12 V through an H-bridge whose total conducting voltage drop is 2 V. Ignoring inductance, what approximate stall current must the driver tolerate?

51 A motor is rapidly decelerated using regenerative braking, and the shared DC supply cannot absorb returned energy. Which failure mode is most likely without additional protection?

52 An H-bridge datasheet defines IN1 = IN2 = 0 as coast and IN1 = IN2 = 1 as brake. Why is assuming that equal inputs always mean the same motor state unsafe?

53 A hobby servo expects pulses from 1.0 ms to 2.0 ms in a 20 ms frame. If PWM is configured at 50 Hz, which nominal duty-cycle range represents those pulse widths?

54 A stepper must move 1000 steps from rest and stop at the destination. The acceleration magnitude is , and the requested maximum speed is . Ignoring discrete-step effects, what profile is feasible?

55 For a stepper accelerating from rest with constant angular acceleration, how should the interval between successive step pulses change approximately as the step index increases?

56 A designer changes a stepper from full-step to 16× microstepping and assumes usable positioning accuracy improves exactly 16× under load. Which limitation most directly invalidates that assumption?

57 Why can a DMA-generated GPIO waveform have substantially lower timing jitter than a Python loop that repeatedly writes GPIO registers?

58 A DMA waveform engine uses PWM or PCM requests to pace writes to GPIO set and clear registers. What primarily determines the waveform's base time resolution?

59 A DMA engine samples an input pin every . An asynchronous pulse can remain HIGH for only . Which statement is correct?

60 A program builds DMA control blocks and data buffers in normal cached memory, then starts DMA immediately. The DMA engine occasionally reads stale descriptors. Which remedy addresses the underlying issue?