devices: add BR property to AbstractXBeeDevice

SX devices require the BR value to correctly initialize the device protocol.
This value can be read directly from the device when the communication
interface is available, but in some scenarios the communication interface is busy
and the BR value cannot be read, resulting in an error initializing the device.
This commit adds the BR value as a new property that is cached in the device once
it is read, allowing upper layers to retrieve it in order to initialize the device
protocol when the communication interface is busy.

Signed-off-by: Tatiana Leon <tatiana.leon@digi.com>
Signed-off-by: David Escalona <david.escalona@digi.com>

Author: daescalona

digi/xbee/devices.py

@@ -138,6 +138,7 @@ def __init__(self, local_xbee_device=None, serial_port=None,
         self._protocol = None
         self._node_id = None
         self._role = Role.UNKNOWN
+        self._br = None
 
         self._packet_listener = None
         self._packet_sender = None
@@ -243,6 +244,18 @@ def update_device_data_from(self, device):
         if new_hw:
             self._hardware_version = new_hw
 
+        new_br = device.br
+        if new_br != self._br:
+            self._br = new_br
+            # It is not necessary to set the 'updated' flag to 'True' because,
+            # if the 'BR' change occurs between 0 and X or X and 0, it means
+            # the device protocol has changed. When this happens in a remote
+            # device, the device is removed from the network and if it happens
+            # in a local device, the object is re-instantiated. In both cases,
+            # this code is never reached. If the 'BR' change occurs between 1
+            # and 2 or 2 and 1, the device protocol (Digi-Mesh) does not
+            # change, thus it is not necessary to notify any relevant change.
+
         if (isinstance(self, (ZigBeeDevice, RemoteZigBeeDevice))
                 and isinstance(device, (ZigBeeDevice, RemoteZigBeeDevice))):
             new_parent = device.parent
@@ -723,14 +736,13 @@ def determine_protocol(self, hardware_version, firmware_version):
             :class:`.XBeeProtocol`: XBee protocol corresponding to the given
                 hardware and firmware versions.
         """
-        br_value = None
         if hardware_version in (HardwareVersion.SX.code,
                                 HardwareVersion.SX_PRO.code,
                                 HardwareVersion.XB8X.code):
-            br_value = self.get_parameter(ATStringCommand.BR, apply=False)[0]
+            self._br = self.get_parameter(ATStringCommand.BR, apply=False)[0]
 
         return XBeeProtocol.determine_protocol(
-            hardware_version, firmware_version, br_value=br_value)
+            hardware_version, firmware_version, br_value=self._br)
 
     def is_device_info_complete(self):
         """
@@ -2318,6 +2330,16 @@ def log(self):
         """
         return self._log
 
+    @property
+    def br(self):
+        """
+        Returns the BR value of the device.
+
+        Returns:
+            Integer: The BR value of the device.
+        """
+        return self._br
+
 
 class XBeeDevice(AbstractXBeeDevice):
     """
@@ -2493,8 +2515,10 @@ def _do_open(self):
             self._operating_mode = OperatingMode.get(xbee_info[0])
             self._hardware_version = HardwareVersion.get(xbee_info[1])
             self._firmware_version = utils.int_to_bytes(xbee_info[2])
-            self._protocol = self.determine_protocol(
-                self._hardware_version.code, self._firmware_version)
+            self._br = xbee_info[7]
+            self._protocol = XBeeProtocol.determine_protocol(
+                self._hardware_version.code, self._firmware_version,
+                br_value=self._br)
             self._64bit_addr = XBee64BitAddress.from_hex_string(xbee_info[3])
             self._16bit_addr = XBee16BitAddress.from_hex_string(xbee_info[4])
             self._node_id = xbee_info[5]