105 lines
3.6 KiB
Python
105 lines
3.6 KiB
Python
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"""
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CAN Bus decoder for Chapter 10 data types
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Supports Controller Area Network Bus (0x78)
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"""
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import struct
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from typing import Dict, Any, Optional
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from .base import DataTypeDecoder, DecodedPayload
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class CANBusDecoder(DataTypeDecoder):
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"""Decoder for CAN Bus type (0x78)"""
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def __init__(self):
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super().__init__()
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self.data_type_base = 0x78
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self.data_type_name = "CAN Bus"
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self.supported_formats = [0x78]
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def can_decode(self, data_type: int) -> bool:
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return data_type == 0x78
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def get_data_type_name(self, data_type: int) -> str:
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return "Controller Area Network Bus"
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def decode(self, payload: bytes, ch10_header: Dict[str, Any]) -> Optional[DecodedPayload]:
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"""Decode CAN Bus payload"""
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decoded_data = {}
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errors = []
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# Parse IPH
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iph = self._parse_intra_packet_header(payload)
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if iph:
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decoded_data.update(iph)
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data_start = iph['data_start']
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else:
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data_start = 0
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errors.append("Failed to parse intra-packet header")
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# Parse CAN messages
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messages = []
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offset = data_start
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while offset + 16 <= len(payload):
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can_header = self._safe_unpack('<IIII', payload, offset)
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if not can_header:
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break
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can_timestamp, can_id_flags, data_length, reserved = can_header
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# Parse CAN ID and flags
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can_id = can_id_flags & 0x1FFFFFFF
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extended_id = bool(can_id_flags & 0x80000000)
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remote_frame = bool(can_id_flags & 0x40000000)
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error_frame = bool(can_id_flags & 0x20000000)
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message = {
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'timestamp': can_timestamp,
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'can_id': f'0x{can_id:x}',
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'extended_id': extended_id,
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'remote_frame': remote_frame,
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'error_frame': error_frame,
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'data_length': data_length
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}
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# Extract CAN data
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can_data_start = offset + 16
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if can_data_start + data_length <= len(payload):
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can_data = payload[can_data_start:can_data_start + data_length]
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message['data'] = can_data.hex()
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message['data_bytes'] = list(can_data)
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else:
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message['data_error'] = 'Data extends beyond payload'
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messages.append(message)
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offset = can_data_start + max(data_length, 8) # CAN frames are padded to 8 bytes
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if len(messages) >= 100: # Limit output size
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break
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decoded_data['can_messages'] = messages
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decoded_data['message_count'] = len(messages)
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# Statistics
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if messages:
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extended_count = sum(1 for msg in messages if msg['extended_id'])
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remote_count = sum(1 for msg in messages if msg['remote_frame'])
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error_count = sum(1 for msg in messages if msg['error_frame'])
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decoded_data['statistics'] = {
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'extended_frames': extended_count,
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'remote_frames': remote_count,
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'error_frames': error_count,
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'standard_frames': len(messages) - extended_count
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}
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return DecodedPayload(
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data_type=0x78,
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data_type_name="Controller Area Network Bus",
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format_version=0,
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decoded_data=decoded_data,
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raw_payload=payload,
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errors=errors,
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metadata={'decoder': 'CANBusDecoder'}
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)
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