BLE advertising and scanning in IOT Protocols - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start BLE advertising with a device name.

IOT Protocols

ble_advertiser.start_advertising(device_name=[1])

Drag options to blanks, or click blank then click option'

ATrue

B12345

C"MyDevice"

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Using a number instead of a string for the device name.

The device name must be a string to advertise properly.

2fill in blank

medium

Complete the code to scan for BLE devices for 10 seconds.

IOT Protocols

scanner.scan(duration=[1])

Drag options to blanks, or click blank then click option'

A10

B5

C"10"

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Passing duration as a string instead of an integer.

The scan duration should be an integer representing seconds.

3fill in blank

hard

Fix the error in the code to stop BLE advertising.

IOT Protocols

ble_advertiser.[1]()

Drag options to blanks, or click blank then click option'

Astart

Bstop_advertising

Cend

Dstop

Attempts:

3 left

💡 Hint

Common Mistakes

Using a non-existent method like stop_advertising.

The correct method to stop advertising is stop().

4fill in blank

hard

Fill both blanks to filter scanned devices by RSSI and device name prefix.

IOT Protocols

filtered_devices = [dev for dev in scanner.scan_results if dev.rssi [1] -70 and dev.name.startswith([2])]

Drag options to blanks, or click blank then click option'

A>

B<

C"My"

D"Device"

Attempts:

3 left

💡 Hint

Common Mistakes

Using < instead of > for RSSI comparison.

Using wrong string prefix.

We want devices with RSSI stronger than -70 (greater than -70) and names starting with "My".

5fill in blank

hard

Fill all four blanks to create a dictionary of device names and RSSI values for devices with names containing 'Sensor' and RSSI less than -60.

IOT Protocols

device_info = {dev.[1]: dev.[2] for dev in scanner.scan_results if 'Sensor' in dev.[3] and dev.rssi [4] -60}

Drag options to blanks, or click blank then click option'

Aname

Brssi

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong attribute names.

Using > instead of < for RSSI filter.

The dictionary keys are device names, values are RSSI. We filter devices whose name contains 'Sensor' and RSSI less than -60.

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