69 lines
1.3 KiB
Python
69 lines
1.3 KiB
Python
import struct
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UBX_SYNC_WORD = b'\xb5\x62'
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def checksum(data: bytes) -> bytes:
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ck_a = 0
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ck_b = 0
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for i in range(len(data)):
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ck_a = (ck_a + data[i]) & 0xFF
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ck_b = (ck_b + ck_a) & 0xFF
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return struct.pack("BB", ck_a, ck_b)
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def frame_create(_class: int, _id: int, _data: bytes) -> bytes:
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_sync = b'\xb5\x62'
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_hdr = struct.pack('B', _class)
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_hdr += struct.pack('B', _id)
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_hdr += struct.pack('<H', len(_data))
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_check = checksum(_hdr + _data)
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return _sync + _hdr + _data + _check
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class Hdr:
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def __init__(self, _class: int, _id: int, _length: int):
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self.mclass = _class
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self.mid = _id
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self.length = _length
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def frame_parse_hdr(frame: bytes) -> Hdr|None:
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hdr = Hdr(0,0,0)
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if len(frame) < 4:
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return None
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hdr.mclass = struct.unpack('B', frame[0:1])[0]
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hdr.mid = struct.unpack('B', frame[1:2])[0]
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hdr.length = struct.unpack('<H', frame[2:4])[0]
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return hdr
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def frame_parse(frame: bytes):
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_data = None
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_hdr = Hdr(0,0,0)
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while True:
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_hdr = frame_parse_hdr(frame[0:4])
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if _hdr is None:
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break
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if (4+_hdr.length+2) != len(frame):
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break
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_check_soll = frame[-2:]
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_check_ist = checksum(frame[0:-2])
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if _check_soll != _check_ist:
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break
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_data = frame[4:-2]
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break
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return _data, _hdr
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if __name__ == "__main__":
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result = frame_create(1, 2, b'Hallo')
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print(result)
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payload, hdr = frame_parse(result)
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print(payload)
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