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Advanced Python BLE example with python-glib and Bluez5
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| import dbus | |
| import time | |
| """ | |
| This gist will do the following things : | |
| 1. Setup GLib and a MainLoop. MainLoop is required to receive signals from the dbus | |
| 2. Define a simple callback function that will be associated to the signal "Properties Changed" for a specific object (Characteristic). | |
| The callback function will be called when the characteristic value is updated or it's property changed. | |
| 3. Build a Proxy object for the Adapter (see adapter-api) and perform a 10 seconds scan (methods StartDiscovery/StopDiscovery). | |
| After the scan, the adapter is introspected and analyzed to find out which devices were discovered. | |
| The first address discovered is used to build a path for the Device Proxy(see 4). | |
| 4. Build a Device Proxy based on the device path built at step 3. Introspect the Device to find the nested Services names. | |
| The name of the second service found during the introspection is used to build a path for the Service Proxy. | |
| I use the second service name since the first Service is usually for properties etc. | |
| 5. Build a Service Proxy based on the service name found at the end of step 4. The Service proxy is introspected to find the | |
| nested characteristic names. The first characteristic name is used to build a path for the Characteristic Proxy. | |
| 6. Build a Characteristic Proxy based on the characteristic name found at the end of step 5. | |
| The method org.bluez.GattCharacteristic1.StartNotify is called to register a "signal receiver". | |
| The callback function will now be called when a signal "Properties Changed is sent to your application by the Characteristic | |
| """ | |
| from dbus.mainloop.glib import DBusGMainLoop | |
| DBusGMainLoop(set_as_default=True) | |
| #Open a connection to the SystemBus | |
| bus = dbus.SystemBus() | |
| """ | |
| This function will be called when a signal "properties-changed" will be sent to your application | |
| """ | |
| def notification_callback(*args, **kwargs): | |
| print("Inside notification callback") | |
| #Build a proxy for the Adapter | |
| adapter_proxy = bus.get_object("org.bluez", "/org/bluez/hci0") | |
| #Call the method StartDiscovery from the adapter api | |
| adapter_proxy.StartDiscovery(dbus_interface="org.bluez.Adapter1") | |
| time.sleep(10); | |
| adapter_proxy.StopDiscovery(dbus_interface="org.bluez.Adapter1") | |
| #Introspect the adapter, print and analyze the xml to find the nearby devices | |
| introspection = adapter_proxy.Introspect(dbus_interface="org.freedesktop.DBus.Introspectable") | |
| #Using lxml library, turn the introspection string into a tree and find the xml tags "node" | |
| #These xml tags nodes will contains the mac addresses of the nearby devices | |
| tree = etree.fromstring(introspection) | |
| #Pretty Print the adapter xml | |
| print etree.tostring(tree, pretty_print=True) | |
| #Parse the xml introspection to find nearby devices | |
| addresses = list() | |
| for child in tree:#Parse the xml tree | |
| if child.tag == 'node': | |
| addresses.append(child.attrib['name']) | |
| #Get the first address found during the xml parsing and build an object path for the Device | |
| device_path = "/org/bluez/hci0/"+addresses[0] | |
| #Build a proxy for the Device using the object path built above | |
| device_proxy = bus.get_object("org.bluez", device_path) | |
| #Connect to the Device using org.bluez.Device1.Connect | |
| device_proxy.Connect(dbus_interface="org.bluez.Device1") | |
| #Repeat the process to find the Services nested in the Device | |
| device_introspection = device_proxy.Introspect(dbus_interface="org.freedesktop.DBus.Introspectable") | |
| tree = etree.fromstring(device_introspection) | |
| services = list() | |
| for child in tree:#Parse the xml tree | |
| if child.tag == 'node': | |
| services.append(child.attrib['name']) | |
| #Get the second Service name found in the introspection xml and build an object path for this Service | |
| service_path = device_path + "/" + services[1] | |
| service_proxy = bus.get_object("org.bluez", "service_path") | |
| #Repeat the process one last time to find the Characteristics nested in the Service | |
| service_introspection = service_proxy.Introspect(dbus_interface="org.freedesktop.DBus.Introspectable") | |
| tree = etree.fromstring(service_introspection) | |
| characteristics = list() | |
| for child in tree: | |
| if child.tag == 'node': | |
| characteristics.append(child.attrib['name']) | |
| #Get the first Characteristic and build the object path | |
| characteristic_path = service_path + "/" + characteristics[0] | |
| characteristic_proxy = bus.get_object("org.bluez", "characteristic_path") | |
| #Call the method org.bluez.GattCharacteristic1.StartNotify | |
| characteristic_proxy.StartNotify(dbus_interface="org.bluez.GattCharacteristic1") | |
| #Register a signal handler that will catch the "Properties Changed". | |
| #The "Properties Changed" signal will emitted when the charcteristic value or properties are changed | |
| bus.add_signal_receiver(notification_callback, dbus_interface="org.freedesktop.DBus.Properties", path=characteristic_path) | |
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