Modification so that testing on the Pi Zeros can utilize their compiled CPP library

src/ble_reticulum/BLEFragmentationBackend.py

@@ -25,7 +25,12 @@ def _requested_backend() -> str:
 
 
 def _load_python_backend():
-    from .BLEFragmentation import BLEFragmenter, BLEReassembler, HDLCFramer
+    try:
+        from .BLEFragmentation import BLEFragmenter, BLEReassembler, HDLCFramer
+    except ImportError:
+        # Reticulum external interfaces can be loaded from a plain interfaces
+        # directory where modules are imported top-level instead of as a package.
+        from BLEFragmentation import BLEFragmenter, BLEReassembler, HDLCFramer
 
     return "python", BLEFragmenter, BLEReassembler, HDLCFramer
 

src/ble_reticulum/BLEInterface.py

@@ -76,13 +76,19 @@ except ImportError:
     sys.path.insert(0, os.path.join(os.path.dirname(__file__), '../../../'))
     from RNS.Interfaces.Interface import Interface
 
-# Import fragmentation module
-# Note: When loaded as external interface, use absolute imports
+# Import fragmentation backend selector.
+# Note: When loaded as external interface, use absolute imports.
 try:
-    from BLEFragmentation import BLEFragmenter, BLEReassembler
+    from BLEFragmentationBackend import BLEFragmenter, BLEReassembler
 except ImportError:
-    # Fallback for when loaded as part of RNS package
-    from ble_reticulum.BLEFragmentation import BLEFragmenter, BLEReassembler
+    try:
+        from ble_reticulum.BLEFragmentationBackend import BLEFragmenter, BLEReassembler
+    except ImportError:
+        # Compatibility fallback if the backend shim is not installed.
+        try:
+            from BLEFragmentation import BLEFragmenter, BLEReassembler
+        except ImportError:
+            from ble_reticulum.BLEFragmentation import BLEFragmenter, BLEReassembler
 
 # Import GATT server for peripheral mode
 try: