338 lines
13 KiB
ReStructuredText
338 lines
13 KiB
ReStructuredText
:mod:`ubluetooth` --- low-level Bluetooth
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=========================================
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.. module:: ubluetooth
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:synopsis: Low-level Bluetooth radio functionality
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This module provides an interface to a Bluetooth controller on a board.
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Currently this supports Bluetooth Low Energy (BLE) in Central, Peripheral,
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Broadcaster, and Observer roles, and a device may operate in multiple
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roles concurrently.
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This API is intended to match the low-level Bluetooth protocol and provide
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building-blocks for higher-level abstractions such as specific device types.
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class BLE
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---------
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Constructor
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-----------
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.. class:: BLE()
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Returns the singleton BLE object.
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Configuration
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-------------
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.. method:: BLE.active([active])
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Optionally changes the active state of the BLE radio, and returns the
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current state.
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The radio must be made active before using any other methods on this class.
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.. method:: BLE.config(name)
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Queries a configuration value by *name*. Currently supported values are:
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- ``'mac'``: Returns the device MAC address. If a device has a fixed address
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(e.g. PYBD) then it will be returned. Otherwise (e.g. ESP32) a random
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address will be generated when the BLE interface is made active.
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Event Handling
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--------------
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.. method:: BLE.irq(handler, trigger=0xffff)
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Registers a callback for events from the BLE stack. The *handler* takes two
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arguments, ``event`` (which will be one of the codes below) and ``data``
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(which is an event-specific tuple of values).
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The optional *trigger* parameter allows you to set a mask of events that
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your program is interested in. The default is all events.
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An event handler showing all possible events::
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def bt_irq(event, data):
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if event == _IRQ_CENTRAL_CONNECT:
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# A central has connected to this peripheral.
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conn_handle, addr_type, addr = data
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elif event == _IRQ_CENTRAL_DISCONNECT:
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# A central has disconnected from this peripheral.
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conn_handle, addr_type, addr = data
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elif event == _IRQ_GATTS_WRITE:
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# A central has written to this characteristic or descriptor.
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conn_handle, attr_handle = data
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elif event == _IRQ_GATTS_READ_REQUEST:
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# A central has issued a read. Note: this is a hard IRQ.
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# Return None to deny the read.
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# Note: This event is not supported on ESP32.
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conn_handle, attr_handle = data
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elif event == _IRQ_SCAN_RESULT:
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# A single scan result.
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addr_type, addr, connectable, rssi, adv_data = data
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elif event == _IRQ_SCAN_COMPLETE:
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# Scan duration finished or manually stopped.
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pass
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elif event == _IRQ_PERIPHERAL_CONNECT:
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# A successful gap_connect().
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conn_handle, addr_type, addr = data
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elif event == _IRQ_PERIPHERAL_DISCONNECT:
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# Connected peripheral has disconnected.
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conn_handle, addr_type, addr = data
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elif event == _IRQ_GATTC_SERVICE_RESULT:
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# Called for each service found by gattc_discover_services().
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conn_handle, start_handle, end_handle, uuid = data
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elif event == _IRQ_GATTC_CHARACTERISTIC_RESULT:
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# Called for each characteristic found by gattc_discover_services().
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conn_handle, def_handle, value_handle, properties, uuid = data
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elif event == _IRQ_GATTC_DESCRIPTOR_RESULT:
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# Called for each descriptor found by gattc_discover_descriptors().
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conn_handle, dsc_handle, uuid = data
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elif event == _IRQ_GATTC_READ_RESULT:
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# A gattc_read() has completed.
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conn_handle, value_handle, char_data = data
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elif event == _IRQ_GATTC_WRITE_STATUS:
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# A gattc_write() has completed.
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conn_handle, value_handle, status = data
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elif event == _IRQ_GATTC_NOTIFY:
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# A peripheral has sent a notify request.
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conn_handle, value_handle, notify_data = data
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elif event == _IRQ_GATTC_INDICATE:
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# A peripheral has sent an indicate request.
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conn_handle, value_handle, notify_data = data
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The event codes are::
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from micropython import const
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_IRQ_CENTRAL_CONNECT = const(1 << 0)
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_IRQ_CENTRAL_DISCONNECT = const(1 << 1)
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_IRQ_GATTS_WRITE = const(1 << 2)
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_IRQ_GATTS_READ_REQUEST = const(1 << 3)
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_IRQ_SCAN_RESULT = const(1 << 4)
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_IRQ_SCAN_COMPLETE = const(1 << 5)
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_IRQ_PERIPHERAL_CONNECT = const(1 << 6)
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_IRQ_PERIPHERAL_DISCONNECT = const(1 << 7)
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_IRQ_GATTC_SERVICE_RESULT = const(1 << 8)
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_IRQ_GATTC_CHARACTERISTIC_RESULT = const(1 << 9)
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_IRQ_GATTC_DESCRIPTOR_RESULT = const(1 << 10)
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_IRQ_GATTC_READ_RESULT = const(1 << 11)
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_IRQ_GATTC_WRITE_STATUS = const(1 << 12)
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_IRQ_GATTC_NOTIFY = const(1 << 13)
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_IRQ_GATTC_INDICATE = const(1 << 14)
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In order to save space in the firmware, these constants are not included on the
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:mod:`ubluetooth` module. Add the ones that you need from the list above to your
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program.
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Broadcaster Role (Advertiser)
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-----------------------------
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.. method:: BLE.gap_advertise(interval_us, adv_data=None, resp_data=None, connectable=True)
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Starts advertising at the specified interval (in **micro**\ seconds). This
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interval will be rounded down to the nearest 625us. To stop advertising, set
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*interval_us* to ``None``.
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*adv_data* and *resp_data* can be any type that implements the buffer
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protocol (e.g. ``bytes``, ``bytearray``, ``str``). *adv_data* is included
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in all broadcasts, and *resp_data* is send in reply to an active scan.
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Note: if *adv_data* (or *resp_data*) is ``None``, then the data passed
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to the previous call to ``gap_advertise`` will be re-used. This allows a
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broadcaster to resume advertising with just ``gap_advertise(interval_us)``.
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To clear the advertising payload pass an empty ``bytes``, i.e. ``b''``.
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Observer Role (Scanner)
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-----------------------
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.. method:: BLE.gap_scan(duration_ms, [interval_us], [window_us])
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Run a scan operation lasting for the specified duration (in **milli**\ seconds).
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To scan indefinitely, set *duration_ms* to ``0``.
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To stop scanning, set *duration_ms* to ``None``.
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Use *interval_us* and *window_us* to optionally configure the duty cycle.
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The scanner will run for *window_us* **micro**\ seconds every *interval_us*
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**micro**\ seconds for a total of *duration_ms* **milli**\ seconds. The default
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interval and window are 1.28 seconds and 11.25 milliseconds respectively
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(background scanning).
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For each scan result, the ``_IRQ_SCAN_RESULT`` event will be raised.
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When scanning is stopped (either due to the duration finishing or when
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explicitly stopped), the ``_IRQ_SCAN_COMPLETE`` event will be raised.
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Peripheral Role (GATT Server)
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-----------------------------
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A BLE peripheral has a set of registered services. Each service may contain
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characteristics, which each have a value. Characteristics can also contain
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descriptors, which themselves have values.
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These values are stored locally, and are accessed by their "value handle" which
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is generated during service registration. They can also be read from or written
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to by a remote central device. Additionally, a peripheral can "notify" a
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characteristic to a connected central via a connection handle.
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Characteristics and descriptors have a default maximum size of 20 bytes.
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Anything written to them by a central will be truncated to this length. However,
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any local write will increase the maximum size, so if you want to allow larger
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writes from a central to a given characteristic, use
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:meth:`gatts_write<BLE.gatts_write>` after registration. e.g.
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``gatts_write(char_handle, bytes(100))``.
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.. method:: BLE.gatts_register_services(services_definition)
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Configures the peripheral with the specified services, replacing any
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existing services.
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*services_definition* is a list of **services**, where each **service** is a
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two-element tuple containing a UUID and a list of **characteristics**.
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Each **characteristic** is a two-or-three-element tuple containing a UUID, a
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**flags** value, and optionally a list of *descriptors*.
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Each **descriptor** is a two-element tuple containing a UUID and a **flags**
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value.
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The **flags** are a bitwise-OR combination of the
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:data:`ubluetooth.FLAGS_READ`, :data:`bluetooth.FLAGS_WRITE` and
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:data:`ubluetooth.FLAGS_NOTIFY` values defined below.
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The return value is a list (one element per service) of tuples (each element
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is a value handle). Characteristics and descriptor handles are flattened
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into the same tuple, in the order that they are defined.
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The following example registers two services (Heart Rate, and Nordic UART)::
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HR_UUID = bluetooth.UUID(0x180D)
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HR_CHAR = (bluetooth.UUID(0x2A37), bluetooth.FLAG_READ | bluetooth.FLAG_NOTIFY,)
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HR_SERVICE = (HR_UUID, (HR_CHAR,),)
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UART_UUID = bluetooth.UUID('6E400001-B5A3-F393-E0A9-E50E24DCCA9E')
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UART_TX = (bluetooth.UUID('6E400003-B5A3-F393-E0A9-E50E24DCCA9E'), bluetooth.FLAG_READ | bluetooth.FLAG_NOTIFY,)
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UART_RX = (bluetooth.UUID('6E400002-B5A3-F393-E0A9-E50E24DCCA9E'), bluetooth.FLAG_WRITE,)
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UART_SERVICE = (UART_UUID, (UART_TX, UART_RX,),)
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SERVICES = (HR_SERVICE, UART_SERVICE,)
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( (hr,), (tx, rx,), ) = bt.gatts_register_services(SERVICES)
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The three value handles (``hr``, ``tx``, ``rx``) can be used with
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:meth:`gatts_read <BLE.gatts_read>`, :meth:`gatts_write <BLE.gatts_write>`,
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and :meth:`gatts_notify <BLE.gatts_notify>`.
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**Note:** Advertising must be stopped before registering services.
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.. method:: BLE.gatts_read(value_handle)
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Reads the local value for this handle (which has either been written by
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:meth:`gatts_write <BLE.gatts_write>` or by a remote central).
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.. method:: BLE.gatts_write(value_handle, data)
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Writes the local value for this handle, which can be read by a central.
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.. method:: BLE.gatts_notify(conn_handle, value_handle, [data])
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Notifies a connected central that this value has changed and that it should
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issue a read of the current value from this peripheral.
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If *data* is specified, then the that value is sent to the central as part
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of the notification, avoiding the need for a separate read request. Note
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that this will not update the local value stored.
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.. method:: BLE.gatts_set_buffer(value_handle, len, append=False)
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Sets the internal buffer size for a value in bytes. This will limit the
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largest possible write that can be received. The default is 20.
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Setting *append* to ``True`` will make all remote writes append to, rather
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than replace, the current value. At most *len* bytes can be buffered in
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this way. When you use :meth:`gatts_read <BLE.gatts_read>`, the value will
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be cleared after reading. This feature is useful when implementing something
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like the Nordic UART Service.
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Central Role (GATT Client)
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--------------------------
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.. method:: BLE.gap_connect(addr_type, addr, scan_duration_ms=2000)
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Connect to a peripheral.
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On success, the ``_IRQ_PERIPHERAL_CONNECT`` event will be raised.
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.. method:: BLE.gap_disconnect(conn_handle)
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Disconnect the specified connection handle.
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On success, the ``_IRQ_PERIPHERAL_DISCONNECT`` event will be raised.
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Returns ``False`` if the connection handle wasn't connected, and ``True``
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otherwise.
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.. method:: BLE.gattc_discover_services(conn_handle)
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Query a connected peripheral for its services.
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For each service discovered, the ``_IRQ_GATTC_SERVICE_RESULT`` event will be
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raised.
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.. method:: BLE.gattc_discover_characteristics(conn_handle, start_handle, end_handle)
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Query a connected peripheral for characteristics in the specified range.
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For each characteristic discovered, the ``_IRQ_GATTC_CHARACTERISTIC_RESULT``
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event will be raised.
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.. method:: BLE.gattc_discover_descriptors(conn_handle, start_handle, end_handle)
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Query a connected peripheral for descriptors in the specified range.
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For each descriptor discovered, the ``_IRQ_GATTC_DESCRIPTOR_RESULT`` event
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will be raised.
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.. method:: BLE.gattc_read(conn_handle, value_handle)
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Issue a remote read to a connected peripheral for the specified
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characteristic or descriptor handle.
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On success, the ``_IRQ_GATTC_READ_RESULT`` event will be raised.
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.. method:: BLE.gattc_write(conn_handle, value_handle, data)
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Issue a remote write to a connected peripheral for the specified
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characteristic or descriptor handle.
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On success, the ``_IRQ_GATTC_WRITE_STATUS`` event will be raised.
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class UUID
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----------
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Constructor
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-----------
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.. class:: UUID(value)
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Creates a UUID instance with the specified **value**.
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The **value** can be either:
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- A 16-bit integer. e.g. ``0x2908``.
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- A 128-bit UUID string. e.g. ``'6E400001-B5A3-F393-E0A9-E50E24DCCA9E'``.
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Constants
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---------
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.. data:: ubluetooth.FLAG_READ
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ubluetooth.FLAG_WRITE
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ubluetooth.FLAG_NOTIFY
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