Tag version 0.2.0

Signed-off-by: Shin'ichiro Kawasaki <kawasaki@juno.dti.ne.jp>

README.md

@@ -186,3 +186,19 @@ In Case You Fail to Connect
 
 3. If scratch_link.py says "failed to connect to BT device: [Errno 13] Permission denied",
    make sure to pair the bluetooth device to your PC before connecting to Scratch.
+
+Issus Reporting
+---------------
+
+Please file issues to [GitHub issue tracker](https://github.com/kawasaki/pyscrlink/issues).
+
+Releases
+--------
+
+Release 0.2.0
+
+* Latency issue fix for BLE devices' write characteristics
+
+Release 0.1.0
+
+* Initial release

pyscrlink/scratch_link.py

@@ -423,6 +423,7 @@ class BLESession(Session):
         self.deviceName = None
         self.perip = None
         self.delegate = None
+        self.characteristics_cache = []
 
     def close(self):
         self.status = self.DONE
@@ -490,6 +491,25 @@ class BLESession(Session):
             charas = self.perip.getCharacteristics(uuid=chara_id)
             return charas[0]
 
+    def _cache_characteristics(self):
+        if not self.perip:
+            return
+        with self.lock:
+            self.characteristics_cache = self.perip.getCharacteristics()
+        if not self.characteristics_cache:
+            logger.debug("Characteristics are not cached")
+
+    def _get_characteristic_cached(self, chara_id):
+        if not self.perip:
+            return None
+        if not self.characteristics_cache:
+            self._cache_characteristics()
+        if self.characteristics_cache:
+            for characteristic in self.characteristics_cache:
+                if characteristic.uuid == chara_id:
+                    return characteristic
+        return _get_characteristic(chara_id)
+
     def handle_request(self, method, params):
         """Handle requests from Scratch"""
         if self.delegate:
@@ -558,6 +578,7 @@ class BLESession(Session):
                 self.status = self.CONNECTED
                 self.delegate = self.BLEDelegate(self)
                 self.perip.withDelegate(self.delegate)
+                self._cache_characteristics()
             else:
                 err_msg = f"BLE connect failed: {self.deviceName}"
                 res["error"] = { "message": err_msg }
@@ -595,7 +616,7 @@ class BLESession(Session):
             logger.debug("handle write request")
             service_id = params['serviceId']
             chara_id = params['characteristicId']
-            c = self._get_characteristic(chara_id)
+            c = self._get_characteristic_cached(chara_id)
             if not c or c.uuid != UUID(chara_id):
                 logger.error(f"Failed to get characteristic {chara_id}")
                 self.status = self.DONE

setup.py

@@ -5,7 +5,7 @@ with open("README.md", "r") as fh:
 
 setuptools.setup(
     name="pyscrlink",
-    version="0.1.0",
+    version="0.2.0",
     author="Shin'ichiro Kawasaki",
     author_email='kawasaki@juno.dti.ne.jp',
     description='Scratch-link for Linux with Python',