Unit 5: Bluetooth with NodeMCU - Practice Quiz

1 What type of wireless communication is used by Bluetooth?

2 Which Bluetooth device usually sends data to a NodeMCU project?

3 What must two Bluetooth devices do before exchanging data?

4 What is the main purpose of a Bluetooth interface in a NodeMCU project?

5 Which connection is normally required for short-range Bluetooth communication?

6 What converts spoken words into commands for a voice-controlled Bluetooth device?

7 In a voice-controlled Bluetooth project, what does the smartphone commonly do?

8 What is the role of the NodeMCU after receiving a voice command?

9 Which command could be used in a simple voice-controlled device?

10 What is an important requirement for a voice-controlled Bluetooth system?

11 What does LCD stand for?

12 What is the main advantage of connecting an LCD through I2C?

13 Which two signal lines are commonly used by an I2C LCD?

14 What type of information can an LCD connected to NodeMCU display?

15 What is the purpose of an I2C backpack attached to an LCD?

16 What does SPI stand for?

17 Which SPI line carries data from the controller to a peripheral?

18 Which SPI line carries data from a peripheral to the controller?

19 What is the purpose of the SPI clock line?

20 What does I2C stand for?

21 A NodeMCU ESP8266 must exchange text commands with an HC-05 Bluetooth module. Which connection arrangement is most appropriate?

22 A Bluetooth module sends characters correctly at first, but the NodeMCU later displays unreadable symbols. What should be checked first?

23 The HC-05 RX input is rated for lower logic voltage than the NodeMCU transmit signal. Which interface change best protects the module?

24 A NodeMCU program receives Bluetooth bytes faster than it processes them. Which technique most directly reduces the chance of losing a complete command?

25 In a typical voice-controlled NodeMCU system using an HC-05, where is spoken language usually converted into a text command?

26 A lamp should turn on for voice inputs such as Turn on light and turn on light. Which processing step makes command recognition more reliable?

27 A voice application sends FAN ON\r\n, but the program compares the input only with FAN ON. What is the most suitable correction?

28 A voice-controlled motor must stop automatically if the Bluetooth connection becomes inactive. Which design best supports this requirement?

29 An I2C LCD backlight turns on, but no characters appear even though wiring and code are otherwise correct. Which adjustment should be tried first?

30 A program initializes an I2C LCD at address 0x27, but the display does not respond. What is the most useful diagnostic action?

31 Two I2C LCD backpacks have the same fixed address and must be controlled independently by one NodeMCU. Which solution is most appropriate?

32 Why does an I2C backpack reduce the number of NodeMCU pins needed for a parallel character LCD?

33 A NodeMCU communicates with two SPI sensors that use the same clock and data lines. How should it select one sensor at a time?

34 An SPI sensor returns shifted or incorrect values although its wiring is correct. Its datasheet specifies CPOL = 1 and CPHA = 1. What should be changed?

35 Which SPI characteristic allows a controller to transmit and receive one bit during the same clock pulse?

36 An SPI peripheral is reliable at 1 MHz but fails intermittently at 10 MHz with long jumper wires. What is the best first modification?

37 Why are pull-up resistors normally required on I2C SDA and SCL lines?

38 During an I2C transfer, the controller sends an address but receives no acknowledgment. What does this most directly indicate?

39 A slow I2C peripheral holds SCL low after the controller attempts to raise it. Which protocol feature is being used?

40 A NodeMCU must read a register from an I2C sensor without releasing control of the bus between writing the register number and reading its value. Which sequence is appropriate?

41 A NodeMCU receives data from an HC-05 module through a 9600-baud UART configured as 8N1. The firmware blocks for 120 ms while updating another peripheral, and the UART receive buffer holds 64 bytes. What is the most likely result if Bluetooth data arrives continuously during the blocking interval?

42 A Bluetooth sender transmits binary sensor frames over a UART stream. Any byte value, including newline, may occur in the payload. Which framing design most reliably allows the NodeMCU to detect complete frames and reject corrupted ones?

43 An HC-05 sends bytes faster than the NodeMCU application can process them. Hardware flow-control pins are unavailable. Which firmware architecture best minimizes loss while keeping Wi-Fi tasks responsive?

44 A UART Bluetooth link is configured for 115200 baud, 8 data bits, no parity, and 1 stop bit. Ignoring Bluetooth-layer overhead, what is the maximum theoretical payload rate for continuously transmitted UART bytes?

45 A voice-control application may send TURN ON LIGHT, turn on light\r\n, or Turn On Light. Which command-processing strategy provides reliable recognition without accidentally accepting turn on lighting?

46 A voice-controlled heater remains on if the phone disconnects immediately after sending the ON command. Which design best addresses this communication-failure hazard?

47 A phone retries a voice command when its acknowledgment is delayed. The command TOGGLE LAMP may therefore arrive twice, returning the lamp to its original state. Which protocol change best solves this problem?

48 A Bluetooth voice application sends FAN:75\n, but UART callbacks sometimes deliver FA and N:75\n separately. What should the NodeMCU do?

49 An I2C scanner detects an LCD backpack at address 0x3F, but the LCD library was initialized with 0x27. Electrical connections and pull-ups are correct. What is the most direct correction?

50 A PCF8574-based LCD backpack operates an HD44780 display in 4-bit mode. Why must the expander output typically be updated multiple times to send one LCD byte?

51 An LCD backpack permanently connects the HD44780 R/W pin to ground. A developer attempts to poll the LCD busy flag through the PCF8574. Why does this fail?

52 A 20x4 I2C LCD is refreshed by calling clear() and rewriting all characters every 100 ms. The display flickers and I2C traffic delays other sensors. Which redesign is most appropriate?

53 An SPI sensor specifies that data changes on the falling edge and is sampled on the rising edge, with the clock idle low. Which SPI mode should the NodeMCU use?

54 Two SPI peripherals share SCLK, MOSI, and MISO, but require different clock modes and frequencies. Which transaction sequence prevents bus conflicts and configuration errors?

55 A NodeMCU must read a two-byte SPI status register. After sending the read command and address, why does the master usually transmit dummy bytes while receiving the result?

56 An SPI ADC guarantees valid MISO data 35 ns after the sampling edge. The NodeMCU input requires 10 ns of setup time before the next relevant edge. Ignoring other delays and assuming half a clock period is available, what is the highest theoretical SPI clock frequency?

57 An I2C bus uses a 4.7 kΩ pull-up and has 400 pF total capacitance. Using the approximation , what rise time should be expected, and what does it imply for Fast-mode I2C with a 300 ns maximum rise time?

58 Two I2C masters start transmitting simultaneously. One sends a logic 1 while the other sends a logic 0 during the same address bit. What happens on a correctly implemented bus?

59 To read bytes from an I2C device's internal register, a master writes the register address and then reads data without releasing bus ownership. Which bus sequence correctly performs this operation?

60 After a NodeMCU resets during an I2C read, a slave remains in a partial transaction and holds SDA low. Which recovery procedure is generally appropriate before reinitializing the controller?