added frame sequence number processing, fixed frame ordering bug in legacy protocol

Brendan Whitfield · Brendan Whitfield · commit ccdf9ffbb003 · 2015-03-17T19:14:37.000-04:00
diff --git a/obd/elm327.py b/obd/elm327.py
@@ -188,7 +188,7 @@ def __find_primary_ecu(self, messages):
 			# first, try filtering for the standard ECU IDs
 			test = lambda m: m.tx_id == self.__protocol.PRIMARY_ECU
 
-			if bool(filter(test, messages)):
+			if bool([m for m in messages if test(m)]):
 				return self.__protocol.PRIMARY_ECU
 			else:
 				# last resort solution, choose ECU
diff --git a/obd/protocols/protocol_can.py b/obd/protocols/protocol_can.py
@@ -152,8 +152,35 @@ def create_message(self, frames, tx_id):
                 debug("Never received frame marked CF")
                 return None
 
-            # TODO
+            # calculate proper sequence indices from the lower 4 bits given
+            for prev, curr in zip(cf, cf[1:]):
+                # Frame sequence numbers only specify the low order bits, so compute the
+                # full sequence number from the frame number and the last sequence number seen:
+                # 1) take the high order bits from the last_sn and low order bits from the frame
+                seq = (prev.seq_index & ~0x0F) + (curr.seq_index)
+                # 2) if this is more than 7 frames away, we probably just wrapped (e.g.,
+                # last=0x0F current=0x01 should mean 0x11, not 0x01)
+                if seq < prev.seq_index - 7:
+                    # untested
+                    seq += 0x10
+
+                curr.seq_index = seq
+
+            # sort the sequence indices
+            cf = sorted(cf, key=lambda f: f.seq_index)
+
+            # concat these lists together
+            frames = ff + cf
+
+            # ensure that each order byte is consecutive by looking at
+            # them in pairs. (see if anything's missing)
+            indices = [f.seq_index for f in frames]
+            pairs = zip(indices, indices[1:])
+            if not all([p[0]+1 == p[1] for p in pairs]):
+                debug("Recieved multiline response with missing frames")
+                return None
 
+            # TODO: extract message data
 
 
         # chop off the Mode/PID bytes based on the mode number
diff --git a/obd/protocols/protocol_legacy.py b/obd/protocols/protocol_legacy.py
@@ -114,11 +114,11 @@ def create_message(self, frames, tx_id):
 				# etc...         [] [  Data   ]
 
 				# sort the frames by the order byte
-				frames = sorted(frames, key=lambda f: f[2])
+				frames = sorted(frames, key=lambda f: f.data_bytes[2])
 
 				# ensure that each order byte is consecutive by looking at
 				# them in pairs. (see if anything's missing)
-				indices = [f[2] for f in frames]
+				indices = [f.data_bytes[2] for f in frames]
 				pairs = zip(indices, indices[1:])
 				if not all([p[0]+1 == p[1] for p in pairs]):
 					debug("Recieved multiline response with missing frames")
diff --git a/tests/test_protocols.py b/tests/test_protocols.py
@@ -100,6 +100,15 @@ def test_can_11():
 		r = p(["NO DATA", "NO DATA"])
 		assert len(r) == 0
 
+		# multi-line response
+		'''
+		r = p(["7E8 10 13 49 04 01 35 36 30",
+				"7E8 21 32 38 39 34 39 41 43",
+				"7E8 22 00 00 00 00 00 00 31"
+		])
+		assert len(r) == 1
+		'''
+
 
 def test_can_29():
 	pass
