103 lines
3.1 KiB
Python
103 lines
3.1 KiB
Python
import ctypes
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class UDP1553Header(ctypes.Structure):
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"""
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Represents the proprietary UDP header wrapping the MIL-STD-1553 frames.
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Based on the provided reference implementation.
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"""
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_pack_ = 1
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_fields_ = [
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("marker1553", ctypes.c_uint16),
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("vmajor", ctypes.c_uint8),
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("vminor", ctypes.c_uint8),
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("otype", ctypes.c_uint16),
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("ta", ctypes.c_uint8),
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("flags", ctypes.c_uint8),
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("fcounter", ctypes.c_uint32),
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("mcounter", ctypes.c_uint32),
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("scounter", ctypes.c_uint32),
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("mmiss", ctypes.c_uint32),
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("smiss", ctypes.c_uint32),
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("ltt", ctypes.c_uint32),
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("errors", ctypes.c_uint32),
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("bc_reserved", ctypes.c_uint32 * 2),
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("rt_reserved", ctypes.c_uint32 * 2),
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("spare", ctypes.c_uint32 * 3)
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]
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# Constants identifying the packet structure
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MARKER_1553 = 0x1553
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MARKER_END_1553 = 0x5315
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OTYPE_BC = 0x4342
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OTYPE_RT = 0x5452
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# Error codes
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ERR_UNSUPPORTED_VERSION = 1
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ERR_INVALID_SOURCE = 2
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ERR_INVALID_LEN = 3
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ERR_MISSED_MSG_MARKER = 4
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def __init__(self, **kwargs):
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super().__init__(**kwargs)
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if "marker1553" not in kwargs:
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self.marker1553 = self.MARKER_1553
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if "otype" not in kwargs:
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self.otype = self.OTYPE_BC
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class CommandWordStruct(ctypes.Structure):
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"""
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Bit-field representation of a 1553 Command Word.
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"""
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_pack_ = 1
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_fields_ = [
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("word_count", ctypes.c_uint16, 5), # Bit 0-4: Word Count / Mode Code
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("subaddress", ctypes.c_uint16, 5), # Bit 5-9: Subaddress
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("tr_bit", ctypes.c_uint16, 1), # Bit 10: Transmit/Receive (1=Tx)
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("remote_terminal", ctypes.c_uint16, 5)# Bit 11-15: Remote Terminal Address
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]
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class CommandWordUnion(ctypes.Union):
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"""
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Union to access Command Word as raw integer or bit-fields.
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"""
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_pack_ = 1
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_fields_ = [
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("raw", ctypes.c_uint16),
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("struct", CommandWordStruct)
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]
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def __init__(self, rt_addr=0, sub_addr=0, word_count=0, transmit=False):
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super().__init__()
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self.struct.remote_terminal = rt_addr
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self.struct.subaddress = sub_addr
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# According to 1553B, word count 0 usually means 32 words,
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# but logic here depends on specific implementation.
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# We store the value 0-31 directly.
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self.struct.word_count = word_count & 0x1F
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self.struct.tr_bit = 1 if transmit else 0
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class UDP1553MessageHeader(ctypes.Structure):
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"""
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Header for a single 1553 Message inside the UDP packet payload.
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Followed immediately by the raw data words (not included in this struct).
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"""
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_pack_ = 1
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_fields_ = [
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("marker", ctypes.c_uint16),
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("command_word", CommandWordUnion),
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("status_word", ctypes.c_uint16),
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("error_code", ctypes.c_uint16)
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]
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MARKER_BEGIN = 0x3C3C
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MARKER_END = 0x3E3E
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def __init__(self, command_word_union=None):
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super().__init__()
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self.marker = self.MARKER_BEGIN
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if command_word_union:
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self.command_word = command_word_union
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self.error_code = 0 |