ETSI Layer2 implementation; stage1: link control analysis

dmrtools/dmrproto/__init__.py

@@ -1,2 +1,3 @@
 from .mmdvm_l1 import *
+from .etsi_l2 import *
 from .exceptions import *

dmrtools/dmrproto/etsi_l2.py

@@ -0,0 +1,50 @@
+from __future__ import annotations
+
+import enum
+
+from abc import ABC, abstractmethod
+from bitarray import bitarray
+from dmr_utils3.bptc import decode_full_lc
+
+from .exceptions import DMRPL2BadDataException
+
+
+class DMRPL2Base(ABC):
+    DataTypes = enum.StrEnum('DataTypes', [
+        'UNKNOWN', 'FULL_LC', 'VOICE_BURST'
+    ])
+
+    def __init__(self, data: bytes) -> None:
+        self.set_data(data)
+
+    def set_data(self, data: bytes) -> None:
+        if len(data) != 33:
+            DMRPL2BadDataException("Data must be 33 bytes long")
+
+        self.bitdata: bitarray = bitarray(data, endian='big')
+
+    def get_data(self) -> bytes:
+        return self.bitdata.tobytes()
+
+    @abstractmethod
+    def get_data_type(self) -> DMRPL2Base.DataTypes:
+        pass
+
+
+class DMRPL2FullLC(DMRPL2Base):
+    def get_data_type(self) -> DMRPL2Base.DataTypes:
+        return DMRPL2Base.DataTypes.FULL_LC
+
+    def get_full_lc(self) -> bytes:
+        return decode_full_lc(self.bitdata[:98] + self.bitdata[-98:]).tobytes()
+
+
+class DMRPL2VoiceBurst(DMRPL2Base):
+    def get_data_type(self) -> DMRPL2Base.DataTypes:
+        return DMRPL2Base.DataTypes.VOICE_BURST
+
+    def get_voice_bits(self) -> tuple[bitarray, bitarray]:
+        return (self.bitdata[:108], self.bitdata[-108:])
+
+    def get_emb_lc(self) -> bytes:
+        return self.bitdata[116:148].tobytes()

dmrtools/dmrproto/exceptions.py

@@ -18,8 +18,15 @@ class DMRPUnknownPacketTypeException(Exception):
     pass
 
 
-class DMRPBadPacket(Exception):
+class DMRPBadPacketException(Exception):
     """
-    Exception raised when a packet is structurally invalid or corrupted.
+    Exception raised when a packet is structurally invalid or corrupted
+    """
+    pass
+
+
+class DMRPL2BadDataException(Exception):
+    """
+    Exception raised when L2 data is invalid or corrupted.
     """
     pass

dmrtools/dmrproto/mmdvm_l1.py

@@ -8,9 +8,10 @@ from hashlib import sha256
 from typing import Type, Self
 
 from .base_fields import DMRPFieldInt, DMRPFieldBytes, DMRPFieldStr
-from .exceptions import DMRPBadPacket
+from .exceptions import DMRPBadPacketException
 from .exceptions import DMRPFieldOutOfRangeException
 from .exceptions import DMRPUnknownPacketTypeException
+from .etsi_l2 import DMRPL2Base, DMRPL2FullLC, DMRPL2VoiceBurst
 
 
 #############################
@@ -66,14 +67,14 @@ class DMRPBasePacket(ABC):
             data (bytes): The raw data from which to create a packet.
 
         Raises:
-            DMRPBadPacket: if size or type doesn't match
+            DMRPBadPacketException: if size or type doesn't match
         """
         self._data = None
         if not data.startswith(self.PKT_TYPE):
-            raise DMRPBadPacket(
+            raise DMRPBadPacketException(
                 f"Bad packet type: '{data[0:4]!r}', expected '{self.PKT_TYPE!r}'")
         if len(data) != self.PKT_SIZE:
-            raise DMRPBadPacket(
+            raise DMRPBadPacketException(
                 f"Bad packet size: {len(data)}, expected {self.PKT_SIZE}")
         self._data = bytearray(data)
 
@@ -296,6 +297,10 @@ class DMRPPacketData(DMRPBasePeerPacket):
     ber       = DMRPFieldInt('ber', 53, 1)
     rssi      = DMRPFieldInt('rssi', 54, 1)
 
+    def __init__(self, data: bytes|None = None) -> None:
+        self.__l2: DMRPL2Base|None = None
+        super().__init__(data)
+
     def set_random_stream_id(self) -> None:
         self.stream_id = int.from_bytes(random.randbytes(4), byteorder="big")
 
@@ -375,6 +380,42 @@ class DMRPPacketData(DMRPBasePeerPacket):
     def is_voice_term(self) -> bool:
         return self.voice_type == DMRPPacketData.VoiceType.TERM
 
+    def get_l2(self) -> DMRPL2Base|None:
+        if self.__l2 is not None:
+            return self.__l2
+
+        if self.voice_type in (DMRPPacketData.VoiceType.HEAD,
+                               DMRPPacketData.VoiceType.TERM):
+            self.__l2 = DMRPL2FullLC(self.dmr_data)
+
+        if self.voice_type in (DMRPPacketData.VoiceType.BURST_A,
+                               DMRPPacketData.VoiceType.BURST_B,
+                               DMRPPacketData.VoiceType.BURST_C,
+                               DMRPPacketData.VoiceType.BURST_D,
+                               DMRPPacketData.VoiceType.BURST_E,
+                               DMRPPacketData.VoiceType.BURST_F):
+            self.__l2 = DMRPL2VoiceBurst(self.dmr_data)
+
+        return self.__l2
+
+    def get_full_lc(self) -> bytes|None:
+        l2 = self.get_l2()
+        if type(l2) is DMRPL2FullLC:
+            return l2.get_full_lc()
+        return None
+
+    def get_emb_lc(self) -> bytes|None:
+        l2 = self.get_l2()
+        if type(l2) is DMRPL2VoiceBurst:
+            return l2.get_emb_lc()
+        return None
+
+    def get_lc(self) -> bytes:
+        if ((lcdata := self.get_full_lc()) is not None or
+            (lcdata := self.get_emb_lc()) is not None):
+                return lcdata
+        return b""
+
     def __str__(self) -> str:
         return self.format()
 
@@ -391,7 +432,13 @@ class DMRPPacketData(DMRPBasePeerPacket):
                         f"src:{self.src_id} dst:{self.dst_id} "
                         f"bits:{self.bits:08b}")
             case 'ext':
-                return str(self) + f" data:{self.dmr_data.hex()}"
+                return (self.format('') +
+                        f" data:{self.dmr_data.hex()}")
+
+            case 'l2':
+                return (self.format('') +
+                        f" lc:{self.get_lc().hex()}" +
+                        f" data:{self.dmr_data.hex()}")
 
         # default
         return (f"{self.pkt_type} "

requirements.txt

@@ -1,9 +1,12 @@
 annotated-types==0.7.0
 anyio==4.9.0
 asyncio==3.4.3
+bitarray==3.4.1
+bitstring==4.3.1
 certifi==2025.4.26
 click==8.1.8
 colorama==0.4.6
+dmr-utils3==0.1.29
 dnspython==2.7.0
 email_validator==2.2.0
 fastapi==0.115.12