BLE for wearables and beacons in IOT Protocols - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start scanning for BLE devices.

IOT Protocols

ble_scanner.start_scan([1])

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

Apower=3

Btimeout=10

Cduration=5

Dinterval=20

Attempts:

3 left

💡 Hint

Common Mistakes

Using timeout instead of duration

Confusing interval with scan time

The duration parameter sets how long the scan runs in seconds. Here, 5 seconds is a common scan duration.

2fill in blank

medium

Complete the code to advertise a BLE beacon with a specific UUID.

IOT Protocols

beacon.advertise(uuid=[1])

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

A"beacon-uuid"

B123e4567-e89b-12d3-a456-426614174000

Cuuid-1234

D"123e4567-e89b-12d3-a456-426614174000"

Attempts:

3 left

💡 Hint

Common Mistakes

Not using quotes around the UUID

Using an invalid UUID format

The UUID must be a string enclosed in quotes to be valid in code.

3fill in blank

hard

Fix the error in the code to connect to a BLE device by address.

IOT Protocols

device = ble.connect([1])

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

Adevice_address

B"device_address"

Caddress

Ddevice.addr

Attempts:

3 left

💡 Hint

Common Mistakes

Passing a variable name instead of a string

Missing quotes around the address

The device address must be a string literal, so it needs quotes.

4fill in blank

hard

Fill both blanks to create a dictionary of beacon names and their RSSI values.

IOT Protocols

beacon_data = {device.[1]: device.[2] for device in scanned_devices}

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

Aname

Brssi

Caddress

Duuid

Attempts:

3 left

💡 Hint

Common Mistakes

Using address instead of name

Using uuid instead of rssi

The dictionary keys are beacon names (name) and values are signal strengths (rssi).

5fill in blank

hard

Fill all three blanks to filter scanned devices with RSSI stronger than -70 and create a dictionary with their UUIDs and names.

IOT Protocols

filtered = {device.[1]: device.[2] for device in scanned_devices if device.[3] > -70}

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

Auuid

Bname

Crssi

Daddress

Attempts:

3 left

💡 Hint

Common Mistakes

Using address instead of uuid

Filtering by name instead of rssi

We use uuid as keys, name as values, and filter by rssi signal strength.

Practice

1. What is the main advantage of using BLE (Bluetooth Low Energy) for wearables and beacons?

easy

A. It requires no pairing or security.

B. It provides very high data transfer speeds.

C. It uses very little power, extending battery life.

D. It works only with smartphones.

Solution

1. Step 1: Understand BLE's design goal

   BLE is designed to use minimal power to keep small devices running longer on batteries.

2. Step 2: Compare options

   High speed is not BLE's focus, pairing is often needed, and BLE works with many devices, not just smartphones.

3. Final Answer:

   It uses very little power, extending battery life. -> Option C

4. Quick Check:

   Low power = A [OK]

Hint: Remember BLE is for low power, not high speed [OK]

Common Mistakes:

• Confusing BLE with classic Bluetooth speed
• Thinking BLE needs no pairing always
• Assuming BLE only works with phones

2. Which of the following is the correct BLE advertising packet type used by beacons to broadcast data without connection?

easy

A. Connectable Directed Advertising

B. Extended Advertising

C. Scan Response Advertising

D. Non-Connectable Undirected Advertising

Solution

1. Step 1: Identify advertising types

   Beacons typically use Non-Connectable Undirected Advertising to broadcast data without needing a connection.

2. Step 2: Eliminate other options

   Connectable Directed requires connection, Scan Response is a reply to scans, Extended Advertising is newer but not typical for simple beacons.

3. Final Answer:

   Non-Connectable Undirected Advertising -> Option D

4. Quick Check:

   Beacon broadcasts = Non-Connectable Undirected [OK]

Hint: Beacons broadcast without connection using non-connectable packets [OK]

Common Mistakes:

• Choosing connectable advertising for beacons
• Confusing scan response with advertising
• Assuming extended advertising is always used

3. Given this Python snippet using a BLE library to scan for devices, what will be printed if a beacon advertising with name 'Beacon123' is found?

devices = scanner.scan(5)
for dev in devices:
    if dev.getValueText(9) == 'Beacon123':
        print(f"Found: {dev.addr}")

medium

A. Found:

B. Found: Beacon123

C. Error: getValueText is not a function

D. No output

Solution

1. Step 1: Understand the code logic

   The code scans for 5 seconds, then checks each device's advertised name (type 9) for 'Beacon123'.

2. Step 2: Analyze the print statement

   If found, it prints 'Found: ' plus the device's address, not the name itself.

3. Final Answer:

   Found: <device address> -> Option A

4. Quick Check:

   Print device address when name matches [OK]

Hint: Check what is printed: address, not name [OK]

Common Mistakes:

• Expecting the name printed instead of address
• Thinking getValueText is invalid
• Assuming no output if beacon found

4. You try to connect to a wearable device using its BLE address but get a connection timeout error. Which of these is the most likely cause?

medium

A. The device is advertising as non-connectable only.

B. The device address is invalid format.

C. The scanning duration was too long.

D. The device uses classic Bluetooth, not BLE.

Solution

1. Step 1: Understand connection timeout causes

   If a device advertises as non-connectable, it will not accept connection requests, causing timeout.

2. Step 2: Evaluate other options

   Invalid address would cause immediate error, scanning duration doesn't affect connection, classic Bluetooth devices won't appear in BLE scan.

3. Final Answer:

   The device is advertising as non-connectable only. -> Option A

4. Quick Check:

   Non-connectable device causes timeout [OK]

Hint: Non-connectable advertising means no connections allowed [OK]

Common Mistakes:

• Confusing scanning time with connection issues
• Assuming invalid address causes timeout instead of error
• Mixing classic Bluetooth with BLE scanning

5. You want to read the heart rate data from a wearable using BLE. Which sequence of steps correctly describes the process?

hard

A. Discover GATT services -> Scan for devices -> Connect to device -> Read heart rate characteristic -> Disconnect

B. Scan for devices -> Connect to device -> Discover GATT services -> Read heart rate characteristic using UUID -> Disconnect

C. Connect to device -> Scan for devices -> Read heart rate characteristic -> Discover GATT services -> Disconnect

D. Read heart rate characteristic -> Scan for devices -> Connect to device -> Discover GATT services -> Disconnect

Solution

1. Step 1: Understand BLE data reading workflow

   First, scan to find the device, then connect to it to access its data.

2. Step 2: Discover GATT services and read characteristic

   After connecting, discover services to find the heart rate characteristic by UUID, then read it.

3. Step 3: Disconnect after reading

   Once data is read, disconnect to save power and free resources.

4. Final Answer:

   Scan for devices -> Connect to device -> Discover GATT services -> Read heart rate characteristic using UUID -> Disconnect -> Option B

5. Quick Check:

   Scan -> Connect -> Discover -> Read -> Disconnect [OK]

Hint: Follow BLE steps in order: scan, connect, discover, read, disconnect [OK]

Common Mistakes:

• Trying to read before connecting
• Discovering services before connecting
• Skipping disconnect step