Sending data over Bluetooth in Arduino - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output sent over Bluetooth?

Consider this Arduino code snippet that sends data over Bluetooth using SoftwareSerial. What data will be sent to the Bluetooth device?

Arduino

  #include <SoftwareSerial.h>
  SoftwareSerial BTSerial(10, 11); // RX, TX

  void setup() {
    BTSerial.begin(9600);
    Serial.begin(9600);
  }

  void loop() {
    int sensorValue = 123;
    BTSerial.print("Value:");
    BTSerial.println(sensorValue);
    delay(1000);
    while(true) {}
  }

A Value:123

B Value:123\r\n

C 123\r\n

D Value\r\n123

💡 Hint

Remember that println adds a newline character after the data.

The print sends "Value:" and println sends the number followed by carriage return and newline characters (\r\n). So the full output is "Value:123\r\n".

🧠 Conceptual

intermediate

Which Arduino pins are commonly used for Bluetooth communication with SoftwareSerial?

When using the SoftwareSerial library to communicate with a Bluetooth module on an Arduino Uno, which pins are typically chosen for RX and TX?

A Pins 10 (RX) and 11 (TX)

B Pins 0 (RX) and 1 (TX)

C Pins A0 (RX) and A1 (TX)

D Pins 13 (RX) and 12 (TX)

💡 Hint

Remember that pins 0 and 1 are used for USB serial communication.

Pins 0 and 1 are reserved for USB serial communication with the PC, so using them for Bluetooth causes conflicts. Pins 10 and 11 are commonly used for SoftwareSerial RX and TX to avoid this conflict.

🔧 Debug

advanced

Why does this Bluetooth data transmission fail?

Look at this Arduino code snippet intended to send "Hello" over Bluetooth. Why does it fail to send the data?

Arduino

  #include <SoftwareSerial.h>
  SoftwareSerial BTSerial(10, 11); // RX, TX

  void setup() {
    Serial.begin(9600);
    BTSerial.begin(9600);
  }

  void loop() {
    BTSerial.write("Hello");
    delay(1000);
  }

A The baud rate 9600 is too slow for Bluetooth communication.

B The pins 10 and 11 are reversed for RX and TX.

C The Serial.begin() call is missing.

D The write() function expects a byte or byte array, not a string literal.

💡 Hint

Check the data type expected by write() when sending strings.

The write() function sends raw bytes and expects either a single byte or a byte array with length. Passing a string literal without specifying length causes it to send only the first byte or behave unexpectedly. Using print() or write((const uint8_t*)"Hello", 5) is correct.

📝 Syntax

advanced

Which option causes a syntax error in Bluetooth data sending?

Which of the following Arduino code snippets will cause a syntax error when trying to send data over Bluetooth?

A BTSerial.write((const uint8_t*)"Temp: 25", 8);

B BTSerial.print("Temp: "); BTSerial.println(25);

C BTSerial.print("Temp: " + 25);

D BTSerial.print(String("Temp: ") + 25);

💡 Hint

Check how string concatenation works in Arduino C++.

Option C tries to add a string literal and an integer directly, which is invalid in Arduino C++. This causes a syntax error. Options A, B, and D use valid methods to send data.

🚀 Application

expert

How many bytes are sent over Bluetooth in this code?

Given this Arduino code sending data over Bluetooth, how many bytes are transmitted each time loop() runs?

Arduino

  #include <SoftwareSerial.h>
  SoftwareSerial BTSerial(10, 11); // RX, TX

  void setup() {
    BTSerial.begin(9600);
  }

  void loop() {
    BTSerial.print("A");
    BTSerial.println(123);
    delay(1000);
    while(true) {}
  }

A 6 bytes

B 4 bytes

C 5 bytes

D 3 bytes

💡 Hint

Count each character sent including newline characters added by println.

The print("A") sends 1 byte ('A'). The println(123) sends '1', '2', '3', \r, \n (5 bytes). Total: 6 bytes.