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# This example finds and connects to a BLE temperature sensor (e.g. the one in ble_temperature.py).
# This example demonstrates the low-level bluetooth module. For most
# applications, we recommend using the higher-level aioble library which takes
# care of all IRQ handling and connection management. See
# https://github.com/micropython/micropython-lib/tree/master/micropython/bluetooth/aioble
# and in particular the temp_client.py example included with aioble.
import bluetooth
import random
import struct
import time
import micropython
from ble_advertising import decode_services, decode_name
from micropython import const
_IRQ_CENTRAL_CONNECT = const(1)
_IRQ_CENTRAL_DISCONNECT = const(2)
_IRQ_GATTS_WRITE = const(3)
_IRQ_GATTS_READ_REQUEST = const(4)
_IRQ_SCAN_RESULT = const(5)
_IRQ_SCAN_DONE = const(6)
_IRQ_PERIPHERAL_CONNECT = const(7)
_IRQ_PERIPHERAL_DISCONNECT = const(8)
_IRQ_GATTC_SERVICE_RESULT = const(9)
_IRQ_GATTC_SERVICE_DONE = const(10)
_IRQ_GATTC_CHARACTERISTIC_RESULT = const(11)
_IRQ_GATTC_CHARACTERISTIC_DONE = const(12)
_IRQ_GATTC_DESCRIPTOR_RESULT = const(13)
_IRQ_GATTC_DESCRIPTOR_DONE = const(14)
_IRQ_GATTC_READ_RESULT = const(15)
_IRQ_GATTC_READ_DONE = const(16)
_IRQ_GATTC_WRITE_DONE = const(17)
_IRQ_GATTC_NOTIFY = const(18)
_IRQ_GATTC_INDICATE = const(19)
_ADV_IND = const(0x00)
_ADV_DIRECT_IND = const(0x01)
_ADV_SCAN_IND = const(0x02)
_ADV_NONCONN_IND = const(0x03)
# org.bluetooth.service.environmental_sensing
_ENV_SENSE_UUID = bluetooth.UUID(0x181A)
# org.bluetooth.characteristic.temperature
_TEMP_UUID = bluetooth.UUID(0x2A6E)
# org.bluetooth.characteristic.gap.appearance.xml
_ADV_APPEARANCE_GENERIC_THERMOMETER = const(768)
class BLETemperatureCentral:
def __init__(self, ble):
self._ble = ble
self._ble.active(True)
self._ble.irq(self._irq)
self._reset()
def _reset(self):
# Cached name and address from a successful scan.
self._name = None
self._addr_type = None
self._addr = None
# Cached value (if we have one)
self._value = None
# Callbacks for completion of various operations.
# These reset back to None after being invoked.
self._scan_callback = None
self._conn_callback = None
self._read_callback = None
# Persistent callback for when new data is notified from the device.
self._notify_callback = None
# Connected device.
self._conn_handle = None
self._start_handle = None
self._end_handle = None
self._value_handle = None
def _irq(self, event, data):
if event == _IRQ_SCAN_RESULT:
addr_type, addr, adv_type, rssi, adv_data = data
if adv_type in (_ADV_IND, _ADV_DIRECT_IND) and _ENV_SENSE_UUID in decode_services(
adv_data
):
# Found a potential device, remember it and stop scanning.
self._addr_type = addr_type
self._addr = bytes(
addr
) # Note: addr buffer is owned by caller so need to copy it.
self._name = decode_name(adv_data) or "?"
self._ble.gap_scan(None)
elif event == _IRQ_SCAN_DONE:
if self._scan_callback:
if self._addr:
# Found a device during the scan (and the scan was explicitly stopped).
self._scan_callback(self._addr_type, self._addr, self._name)
self._scan_callback = None
else:
# Scan timed out.
self._scan_callback(None, None, None)
elif event == _IRQ_PERIPHERAL_CONNECT:
# Connect successful.
conn_handle, addr_type, addr = data
if addr_type == self._addr_type and addr == self._addr:
self._conn_handle = conn_handle
self._ble.gattc_discover_services(self._conn_handle)
elif event == _IRQ_PERIPHERAL_DISCONNECT:
# Disconnect (either initiated by us or the remote end).
conn_handle, _, _ = data
if conn_handle == self._conn_handle:
# If it was initiated by us, it'll already be reset.
self._reset()
elif event == _IRQ_GATTC_SERVICE_RESULT:
# Connected device returned a service.
conn_handle, start_handle, end_handle, uuid = data
if conn_handle == self._conn_handle and uuid == _ENV_SENSE_UUID:
self._start_handle, self._end_handle = start_handle, end_handle
elif event == _IRQ_GATTC_SERVICE_DONE:
# Service query complete.
if self._start_handle and self._end_handle:
self._ble.gattc_discover_characteristics(
self._conn_handle, self._start_handle, self._end_handle
)
else:
print("Failed to find environmental sensing service.")
elif event == _IRQ_GATTC_CHARACTERISTIC_RESULT:
# Connected device returned a characteristic.
conn_handle, def_handle, value_handle, properties, uuid = data
if conn_handle == self._conn_handle and uuid == _TEMP_UUID:
self._value_handle = value_handle
elif event == _IRQ_GATTC_CHARACTERISTIC_DONE:
# Characteristic query complete.
if self._value_handle:
# We've finished connecting and discovering device, fire the connect callback.
if self._conn_callback:
self._conn_callback()
else:
print("Failed to find temperature characteristic.")
elif event == _IRQ_GATTC_READ_RESULT:
# A read completed successfully.
conn_handle, value_handle, char_data = data
if conn_handle == self._conn_handle and value_handle == self._value_handle:
self._update_value(char_data)
if self._read_callback:
self._read_callback(self._value)
self._read_callback = None
elif event == _IRQ_GATTC_READ_DONE:
# Read completed (no-op).
conn_handle, value_handle, status = data
elif event == _IRQ_GATTC_NOTIFY:
# The ble_temperature.py demo periodically notifies its value.
conn_handle, value_handle, notify_data = data
if conn_handle == self._conn_handle and value_handle == self._value_handle:
self._update_value(notify_data)
if self._notify_callback:
self._notify_callback(self._value)
# Returns true if we've successfully connected and discovered characteristics.
def is_connected(self):
return self._conn_handle is not None and self._value_handle is not None
# Find a device advertising the environmental sensor service.
def scan(self, callback=None):
self._addr_type = None
self._addr = None
self._scan_callback = callback
self._ble.gap_scan(2000, 30000, 30000)
# Connect to the specified device (otherwise use cached address from a scan).
def connect(self, addr_type=None, addr=None, callback=None):
self._addr_type = addr_type or self._addr_type
self._addr = addr or self._addr
self._conn_callback = callback
if self._addr_type is None or self._addr is None:
return False
self._ble.gap_connect(self._addr_type, self._addr)
return True
# Disconnect from current device.
def disconnect(self):
if self._conn_handle is None:
return
self._ble.gap_disconnect(self._conn_handle)
self._reset()
# Issues an (asynchronous) read, will invoke callback with data.
def read(self, callback):
if not self.is_connected():
return
self._read_callback = callback
self._ble.gattc_read(self._conn_handle, self._value_handle)
# Sets a callback to be invoked when the device notifies us.
def on_notify(self, callback):
self._notify_callback = callback
def _update_value(self, data):
# Data is sint16 in degrees Celsius with a resolution of 0.01 degrees Celsius.
self._value = struct.unpack("<h", data)[0] / 100
return self._value
def value(self):
return self._value
def demo():
ble = bluetooth.BLE()
central = BLETemperatureCentral(ble)
not_found = False
def on_scan(addr_type, addr, name):
if addr_type is not None:
print("Found sensor:", addr_type, addr, name)
central.connect()
else:
nonlocal not_found
not_found = True
print("No sensor found.")
central.scan(callback=on_scan)
# Wait for connection...
while not central.is_connected():
time.sleep_ms(100)
if not_found:
return
print("Connected")
# Explicitly issue reads, using "print" as the callback.
while central.is_connected():
central.read(callback=print)
time.sleep_ms(2000)
# Alternative to the above, just show the most recently notified value.
# while central.is_connected():
# print(central.value())
# time.sleep_ms(2000)
print("Disconnected")
if __name__ == "__main__":
demo()
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