Python BLE discover all UUID characteristics

ONLINECAST

2 min read

·

06-10-2024

11

0

Share

Discovering All UUID Characteristics in a Bluetooth Low Energy Device with Python

Connecting to a Bluetooth Low Energy (BLE) device and discovering its characteristics is a common task for developers working with these devices. However, finding all the characteristics, especially those with unknown UUIDs, can be challenging. This article guides you through a comprehensive approach to discovering all UUID characteristics in a BLE device using Python.

The Challenge: Uncovering Hidden Characteristics

Imagine you have a BLE device with various services and characteristics. Some characteristics might have well-defined UUIDs (like Heart Rate Measurement), while others might have custom, unknown UUIDs. You need to discover all of these characteristics, even the ones with unknown UUIDs, to fully understand the capabilities of the device.

The Solution: Leveraging bluepy for Comprehensive Discovery

Python's bluepy library provides a robust framework for interacting with BLE devices. Here's a breakdown of the code and how it addresses the challenge:

from bluepy.btle import Scanner, DefaultDelegate

class ScanDelegate(DefaultDelegate):
    def handleDiscovery(self, dev, isNewDev, isNewData):
        if isNewDev:
            print("Discovered device:", dev.addr)
        elif isNewData:
            for (adtype, description, value) in dev.getScanData():
                print("  %s = %s" % (description, value))

scanner = Scanner().withDelegate(ScanDelegate())
devices = scanner.scan(5.0)  # Scan for 5 seconds

for dev in devices:
    print("Device %s (%s), RSSI=%d dB" % (dev.addr, dev.addrType, dev.rssi))
    for (handle, char) in dev.getCharacteristics():
        print("  Characteristic:", char.uuid, char.propertiesToString())

Breaking Down the Code:

1. Import Libraries: The code begins by importing the necessary libraries from bluepy, namely Scanner, DefaultDelegate, and ScanDelegate.
2. Custom Delegate: The ScanDelegate class overrides the handleDiscovery method to capture and print information about discovered devices and their advertisement data.
3. Scanning and Discovery: The Scanner object is initialized with the custom delegate. The scan method performs a 5-second scan for BLE devices.
4. Device Information: The code iterates through the discovered devices and prints their address, type, and RSSI (Received Signal Strength Indicator).
5. Characteristic Retrieval: For each device, the getCharacteristics() method retrieves all available characteristics. The code then prints the UUID and properties of each characteristic.

Key Considerations:

• Device Compatibility: The code assumes the device is compatible with bluepy. Make sure your device is discoverable and supports the necessary BLE protocols.
• UUID Interpretation: The char.uuid property will display the UUID in its raw form. You'll need to interpret it based on the BLE standard or the device's documentation.
• Characteristic Properties: The char.propertiesToString() method provides information about the characteristic's properties, such as read, write, notify, and more.

Additional Tips:

• Extended Scan Duration: Increase the scan duration (5 seconds in the example) if you need more time to discover all available devices.
• Specific UUID Filtering: You can filter for specific UUIDs using the getCharacteristics() method with arguments for desired UUIDs.
• Service Discovery: After discovering characteristics, you can further explore the services they belong to for a deeper understanding of the device's structure.

Conclusion:

By understanding how to use bluepy and its tools effectively, you can thoroughly explore the characteristics of any BLE device, including those with unknown UUIDs. This enables you to unlock the full potential of these devices and build powerful applications that leverage their unique capabilities.

Remember: Always refer to the device's documentation for detailed information about its services, characteristics, and specific UUIDs.