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Bluetooth abstraction API package

Project description

BlueST SDK

BlueST is a multi-platform library (Android, iOS, and Linux supported) that permits easy access to the data exported by a Bluetooth Low Energy (BLE) device that implements the BlueST Protocol.

Compatibility

This version of the SDK is compatible with Python 2.7 and runs on a Linux system.

Preconditions

The BlueST SDK makes use of the bluepy Python interface to Bluetooth Low Energy on Linux.

$ sudo pip install bluepy

Moreover, it uses the concurrent.futures module to run pools of threads in background, that serve listeners' callbacks.

$ sudo pip install futures

Please follow the official instructions to install the mentioned libraries.

Setting up the application examples

Before running the application examples, please follow the steps here below.

  • The example_ble_1.py application example shows how to perform a BLE scan, connect to a device, retrieve its exported features, and get push notifications from it. The application requires to set up a device equipped with BLE connectivity and a FW compatible with the BlueST Protocol, e.g. the SensorTile development kit and the FP-SNS-MOTENV1 function pack.
  • The example_ble_2.py application example shows how to connect to a BLE device exporting a "Stepper Motor" feature, to get its status, and to send commands to it. The application requires to set up a device equipped with BLE connectivity and a stepper motor control, e.g.:
    • A NUCLEO-F401RE development board
    • An X-NUCLEO-IDB05A1 Bluetooth Low Energy expansion board
    • An X-NUCLEO-IHM01A1 Stepper Motor Driver expansion board, plus a proper stepper motor
    • Import the Node_BLE_StepperMotor_Device mbed OS application to your ARM mbed account, compile, and flash it onto the MCU board
    • Edit the application example and set the "MOTOR_DEVICE_MAC" global variable with the proper MAC address of your stepper motor enabled BLE device (which you can retrieve for example through a smartphone application)
  • The example_ble_3.py application example shows how to handle two BLE devices exporting a "Switch" feature in such a way that pressing the user button on a device makes the LED of the other device toggle its state, through a logic defined within the application itself. The application requires to set up two devices equipped with BLE connectivity, e.g.:
    • Two NUCLEO-F401RE development boards
    • Two X-NUCLEO-IDB05A1 Bluetooth Low Energy expansion boards
    • Import the Node_BLE_Switch_Device mbed OS application to your ARM mbed account, compile, and flash it onto the MCU board
    • Edit the application example and set the "IOT_DEVICE_X_MAC" global variables properly (you can use a smartphone application to retrieve the MAC address)
  • The example_ble_4.py application example shows how to connect to a microphone-enabled device exporting the "ADPCM Audio" and "ADPCM Sync" features, and allows to reproduce the recorded audio and to dump it on a file. The application requires to set up a device equipped with BLE connectivity and a FW compatible with the BlueST Protocol, e.g. the SensorTile development kit and the FP-SNS-ALLMEMS1 function pack. Please refer to the application example file for the software requirements.

Other application examples can be found within the EdgeST SDK for Linux, an IoT edge computing abstraction library for Linux gateways.

Running the application examples

To run the BlueST application examples please follow the steps below:

  1. Clone the repository containing the BlueST SDK and the BlueST examples into a "BlueSTSDK_Python" folder.
  2. Add the "BlueSTSDK_Python" folder to the "PYTHONPATH" environment variable. On Linux:
    $ export PYTHONPATH=/home/<user>/BlueSTSDK_Python/
    
  3. Enter the BlueST examples folder and run the main scripts:
    $ python example_ble_x.py
    

BlueST Protocol

Advertising data

The library shows only the devices that have a vendor-specific field formatted in the following way:

Length 1 1 1 1 4 6
Name Length Field Type Protocol Version Device Id Feature Mask Device MAC (optional)
Value 0x07/0x0D 0xFF 0x01 0xXX 0xXXXXXXXX 0xXXXXXXXXXXXX

In case you need to define your own custom boards, you should use Device Id values not yet assigned. Moreover, please note that values between 0x80 and 0xFF are reserved for ST Nucleo boards.

  • The feature mask is a bit field that provides information about which features are exported by the board. Currently, bits are mapped in the following way:

    Bit 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
    Feature Analog ADPCM Sync Switch Direction of arrival ADPCM Audio Microphone Level Proximity Luxmeter Accelerometer Gyroscope Magnetometer Pressure Humidity Temperature Battery Second Temperature
    Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
    Feature CO Sensor DC Motor Stepper Motor SD Logging Beam forming Accelerometer Event Free Fall Sensor Fusion Compact Sensor Fusion Motion Intensity Compass Activity Carry Position Proximity Gesture MEMS Gesture Pedometer

To understand the way the data are exported by predefined features, please refer to the method Feature.extract_data(timestamp, data, offset) within the features class definition.

  • The device MAC address is optional, and needed only on the iOS platform.

Note

Currently only a subset of the features is implemented: Switch, Proximity, Accelerometer, Gyroscope, Magnetometer, Pressure, Humidity, Temperature, Second Temperature, Stepper Motor, and Proximity Gesture. Future releases of the Python SDK will cover all the abovementioned features.

Characteristics/Features

The characteristics managed by the SDK must have a UUID as follows: XXXXXXXX-0001-11e1-ac36-0002a5d5c51b. The SDK scans all the services, searching for characteristics that match the pattern.

The first part of the UUID has bits set to "1" for each feature exported by the characteristics.

In case of multiple features mapped onto a single characteristic, the data must be in the same order as the bit mask.

A characteristic's data format must be the following:

Length 2 >1 >1
Name Timestamp First Feature Data Second Feature Data .....

The first 2 bytes are used to communicate a timestamp. This is especially useful to recognize any loss of data.

Since the BLE packet maximum length is 20 bytes, the maximum size of a feature's data field is 18 bytes.

Example

The SDK is compatible with the following ST firmware:

  • FP-SNS-MOTENV1: STM32 ODE function pack for IoT node with BLE connectivity plus environmental and motion sensors
  • FP-SNS-ALLMEMS1: STM32 ODE function pack for IoT node with BLE connectivity, digital microphone, environmental and motion sensors
  • FP-SNS-FLIGHT1: STM32 ODE function pack for IoT node with BLE connectivity, environmental and motion sensors, time-of-flight sensors (Please remove NFC when used with Python SDK)

Main actors

Manager

This is a singleton class that starts/stops the discovery process and stores the retrieved nodes.

Before starting the scanning process, it is also possible to define a new Device Id and to register/add new features to already defined devices.

The Manager notifies a new discovered node through the ManagerListener class. Each callback is performed asynchronously by a thread running in background.

Node

This class represents a remote device.

Through this class it is possible to recover the features exported by a node and read/write data from/to the device.

The node exports all the features whose corresponding bit is set to "1" within the advertising data message. Once the device is connected, scanning and enabling the available characteristics can be performed. Then, it is possible to request/send data related to the discovered features.

A node notifies its RSSI (signal strength) when created.

A node can be in one of following status:

  • Init: dummy initial status.
  • Idle: the node is waiting for a connection and sending an advertising data message.
  • Connecting: a connection with the node was triggered, the node is performing the discovery of device services/characteristics.
  • Connected: connection with the node was successful.
  • Disconnecting: ongoing disconnection; once disconnected the node goes back to the Idle status.
  • Lost: the device has sent an advertising data, however it is not reachable anymore.
  • Unreachable: the connection with the node was in place, however it is not reachable anymore.
  • Dead: dummy final status.

Each callback is performed asynchronously by a thread running in background.

Feature

This class represents the data exported by a node.

Each feature has an array of Field objects that describes the data exported.

Data are received from a BLE characteristic and contained in a Sample class. The user is notified about new data through a listener.

Note that each callback is performed asynchronously by a thread running in background.

Available features can be retrieved from Features package.

How to add a new Feature

  1. Extend the Feature class:

    1. Create an array of Field objects that describe the data exported by the feature.
    2. Create a constructor that accepts only the node as a parameter. From this constructor call the superclass constructor, passing the feature's name and the feature's fields.
    3. Implement the method Feature.extract_data(timestamp, data, offset).
    4. Implement a class method that allows to get data from a Sample object.
  2. Register the new feature: If you want to use BlueST's bitmask for features within the advertising data, please register the new feature before performing the discovery process, e.g.:

    # Adding a 'MyFeature' feature to a Nucleo device and mapping it to a custom
    # '0x10000000-0001-11e1-ac36-0002a5d5c51b' characteristic.
    mask_to_features_dic = {}
    mask_to_features_dic[0x10000000] = my_feature.MyFeature
    try:
        Manager.add_features_to_node(0x80, mask_to_features_dic)
    except InvalidFeatureBitMaskException as e:
        print e
    # Synchronous discovery of Bluetooth devices.
    manager.discover(False, SCANNING_TIME_s)
    

    Otherwise, you can register the feature after discovering a node and before connecting to it:

    # Adding a 'FeatureHeartRate' feature to a Nucleo device and mapping it to
    # the standard '00002a37-0000-1000-8000-00805f9b34fb' Heart Rate Measurement
    # characteristic.
    map = UUIDToFeatureMap()
    map.put(uuid.UUID('00002a37-0000-1000-8000-00805f9b34fb'), feature_heart_rate.FeatureHeartRate)
    node.add_external_features(map)
    # Connecting to the node.
    node.connect()
    

Documentation

Documentation can be found here.

License

COPYRIGHT(c) 2018 STMicroelectronics

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
  2. Redistributions in binary form must reproduce the above notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
  3. Neither the name of STMicroelectronics nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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