Implemented decoder with cantools but more testing required (#349)

* Implemented decoder with cantools but more testing required

* Goodbye match case and removed linting

* Added config to decoder file

py/config.json

@@ -0,0 +1,3 @@
+{
+    "no_lint": true
+}

py/decoder/config.json

@@ -0,0 +1,3 @@
+{
+    "no_lint": true
+}

py/decoder/decoder.py

@@ -0,0 +1,89 @@
+import os
+import pty
+import cantools
+import serial
+
+
+class State:
+    SOM = "SOM"
+    ID = "ID"
+    DLC = "DLC"
+    DATA = "DATA"
+    EOM = "EOM"
+    VALID = "VALID"
+
+
+class DatagramDecoder:
+    def __init__(self):
+        self.message_state = State.SOM
+        self.buffer = []
+        self.datagram = None
+        self.init_serial()
+        self.init_dbc()
+
+    def init_serial(self):
+        self.master, self.slave = pty.openpty()
+        self.slave_name = os.ttyname(self.slave)
+        self.slave_serial = serial.Serial(self.slave_name)
+
+    def init_dbc(self):
+        dbc_path = "/Users/ericgao/box/shared/fwxv/libraries/codegen/system_can.dbc"
+        self.db = cantools.database.load_file(dbc_path)
+
+    def write(self, packet):
+        self.slave_serial.write(bytes(packet))
+
+    def read(self):
+        recv = os.read(self.master, 1000)
+        if self.parse_byte(recv):
+            message = self.db.get_message_by_frame_id(self.datagram["id"])
+            decoded_data = message.decode(self.datagram['data'])
+            print(decoded_data)
+
+    def read_test(self, byte):
+        if self.parse_byte(byte):
+            message = self.db.get_message_by_frame_id(self.datagram["id"])
+            decoded_data = message.decode(bytes(self.datagram['data']))
+            print(decoded_data)
+
+    def is_valid_id(self, id):
+        try:
+            self.db.get_message_by_frame_id(id)
+            return True
+        except KeyError:
+            return False
+
+    def parse_byte(self, byte):
+        if self.message_state == State.SOM or self.message_state == State.VALID:
+            self.buffer = []
+            self.datagram = None
+            if byte == 0xAA:
+                self.message_state = State.ID
+        elif self.message_state == State.ID:
+            self.buffer.append(byte)
+            if len(self.buffer) == 4:
+                message_id = int.from_bytes(self.buffer, byteorder='big')
+                if self.is_valid_id(message_id):
+                    self.datagram = {"id": message_id}
+                    self.buffer = []
+                    self.message_state = State.DLC
+                else:
+                    self.message_state = State.SOM
+        elif self.message_state == State.DLC:
+            self.datagram["dlc"] = byte
+            if self.datagram["dlc"] <= 9:
+                self.datagram["data"] = []
+                self.message_state = State.DATA
+            else:
+                self.message_state = State.SOM
+        elif self.message_state == State.DATA:
+            self.buffer.append(byte)
+            if len(self.buffer) == self.datagram["dlc"]:
+                self.datagram["data"] = self.buffer
+                self.message_state = State.EOM
+        elif self.message_state == State.EOM:
+            if byte == 0xBB:
+                self.message_state = State.VALID
+            else:
+                self.message_state = State.SOM
+        return self.message_state == State.VALID

py/decoder/test.py

@@ -0,0 +1,23 @@
+from decoder import DatagramDecoder
+
+decoder = DatagramDecoder()
+
+invalid_msg = [0xAA, 0xFF, 0x00, 0x00, 0x00, 0x01, 0x06, 0xAA, 0x01, 0x01, 0x01, 0x01, 0x01, 0xBB]
+
+for byte in invalid_msg:
+    decoder.read_test(byte)
+
+valid_msg = [0xAA, 0x00, 0x00, 0x00, 0x01, 0x07, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0xBB]
+
+for byte in valid_msg:
+    decoder.read_test(byte)
+
+invalid_msg = [0xAA, 0x00, 0x00, 0x00, 0x01, 0x07, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0xAA]
+
+for byte in invalid_msg:
+    decoder.read_test(byte)
+
+valid_msg = [0xAA, 0x00, 0x00, 0x00, 0x01, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xBB]
+
+for byte in valid_msg:
+    decoder.read_test(byte)