BLE advertising and scanning in IOT Protocols - Mini Project: Build & Apply

BLE Advertising and Scanning Basics

📖 Scenario: You are working on a simple IoT device that uses Bluetooth Low Energy (BLE) to share its presence and discover other devices nearby. This is common in smart home gadgets and fitness trackers.

🎯 Goal: Build a basic BLE advertising and scanning setup where your device advertises a name and scans for other devices advertising their names.

📋 What You'll Learn

Create a dictionary called advertisement with keys 'name' and 'service_uuid' and exact values 'MyDevice' and '1234'

Create a variable called scan_duration and set it to 5 (seconds)

Write a function called scan_devices that takes scan_duration and returns a list of device names found (simulate with a fixed list)

Print the list of scanned device names

💡 Why This Matters

🌍 Real World

BLE advertising and scanning is used in smart home devices, fitness trackers, and proximity marketing to share and discover device presence.

💼 Career

Understanding BLE basics helps in IoT development, embedded systems, and wireless communication roles.

1

Create BLE advertisement data

Create a dictionary called advertisement with keys 'name' and 'service_uuid' and values 'MyDevice' and '1234' respectively.

IOT Protocols

# Create the advertisement dictionary with name and service_uuid
# Your code here

Hint

Think of advertisement as a small card your device shows to others. It needs a name and a service ID.

2

Set scan duration

Create a variable called scan_duration and set it to the integer 5 representing seconds.

IOT Protocols

advertisement = {'name': 'MyDevice', 'service_uuid': '1234'}
# Set scan_duration to 5 seconds
# Your code here

Hint

This variable controls how long your device listens for others.

3

Write a scanning function

Write a function called scan_devices that takes scan_duration as input and returns a list of device names found. For this exercise, return the fixed list ['DeviceA', 'DeviceB', 'DeviceC'].

IOT Protocols

advertisement = {'name': 'MyDevice', 'service_uuid': '1234'}
scan_duration = 5
# Define scan_devices(scan_duration) function
# Your code here

Hint

This function pretends to look around and find other devices.

4

Print scanned devices

Call the function scan_devices with scan_duration and print the returned list of device names.

IOT Protocols

advertisement = {'name': 'MyDevice', 'service_uuid': '1234'}
scan_duration = 5

def scan_devices(scan_duration):
    # Simulate scanning by returning a fixed list
    return ['DeviceA', 'DeviceB', 'DeviceC']

# Call scan_devices and print the result
# Your code here

Hint

Show the devices your scan found by printing the list.

Practice

1. What is the main purpose of BLE advertising in Bluetooth Low Energy communication?

easy

A. To broadcast small packets of data repeatedly to nearby devices

B. To establish a full connection between devices

C. To encrypt data between devices

D. To scan for other devices' signals

Solution

1. Step 1: Understand BLE advertising role

   BLE advertising sends small data packets repeatedly to announce presence.

2. Step 2: Differentiate from scanning and connection

   Advertising is broadcasting, not scanning or connecting.

3. Final Answer:

   To broadcast small packets of data repeatedly to nearby devices -> Option A

4. Quick Check:

   Advertising = broadcast small data [OK]

Hint: Advertising means sending out info repeatedly [OK]

Common Mistakes:

• Confusing advertising with scanning
• Thinking advertising establishes connections
• Assuming advertising encrypts data

2. Which of the following is the correct command to start BLE scanning using the Linux tool bluetoothctl?

easy

A. ble scan start

B. start scan

C. scan start

D. scan on

Solution

1. Step 1: Recall bluetoothctl scan command

   The correct command to start scanning is exactly scan on.

2. Step 2: Check other options for syntax

   Other options are incorrect commands or invalid syntax in bluetoothctl.

3. Final Answer:

   scan on -> Option D

4. Quick Check:

   bluetoothctl scan on = start scanning [OK]

Hint: Use exact command 'scan on' in bluetoothctl [OK]

Common Mistakes:

• Using 'start scan' instead of 'scan on'
• Typing commands not supported by bluetoothctl
• Confusing scan commands with advertising commands

3. Given this Python snippet using a BLE library to scan devices:

devices = scanner.scan(5.0)
for dev in devices:
    print(dev.addr)

What will this code output?

medium

A. Empty list because scan time is too short

B. List of device addresses found during 5 seconds scan

C. Error because scan() needs no arguments

D. List of device names found during 5 seconds scan

Solution

1. Step 1: Understand scan() usage with timeout

   The scan method scans for devices for given seconds and returns device objects.

2. Step 2: Identify printed attribute

   Printing dev.addr outputs device MAC addresses found.

3. Final Answer:

   List of device addresses found during 5 seconds scan -> Option B

4. Quick Check:

   scan(5.0) returns devices; dev.addr prints addresses [OK]

Hint: scan(timeout) returns devices; print dev.addr for addresses [OK]

Common Mistakes:

• Thinking scan() takes no arguments
• Confusing device address with device name
• Assuming scan always returns empty list

4. You wrote this code to scan BLE devices but get no output:

scanner = Scanner()
devices = scanner.scan()
for dev in devices:
    print(dev.addr)

What is the likely problem?

medium

A. print(dev.addr) is incorrect attribute

B. Scanner() class does not exist

C. Missing scan timeout argument causes no devices found

D. scan() method should be called with 'start' keyword

Solution

1. Step 1: Check scan() method requirements

   scan() requires a timeout argument to specify scan duration.

2. Step 2: Understand effect of missing timeout

   Without timeout, scan may return immediately with no devices.

3. Final Answer:

   Missing scan timeout argument causes no devices found -> Option C

4. Quick Check:

   scan() needs timeout to find devices [OK]

Hint: Always provide scan timeout to get results [OK]

Common Mistakes:

• Omitting scan timeout argument
• Assuming dev.addr is invalid
• Thinking scan() uses 'start' keyword

5. You want to filter BLE scan results to only show devices advertising a specific service UUID. Which approach correctly applies this filter in Python?

hard

A. Use a list comprehension: [dev for dev in devices if '1234' in dev.getScanData()]

B. Check if '1234' in dev.addr for each device

C. Filter devices by comparing dev.name to '1234'

D. Use devices.filter('1234') method directly

Solution

1. Step 1: Understand filtering by service UUID

   Service UUIDs appear in scan data, not in address or name.

2. Step 2: Use list comprehension with getScanData()

   getScanData() returns advertised data; check if UUID '1234' is present.

3. Final Answer:

   Use a list comprehension: [dev for dev in devices if '1234' in dev.getScanData()] -> Option A

4. Quick Check:

   Filter by UUID in scan data using list comprehension [OK]

Hint: Filter devices by checking UUID in scan data list [OK]

Common Mistakes:

• Checking UUID in device address
• Filtering by device name instead of UUID
• Using non-existent filter() method on devices