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# -*- coding: utf-8 -*-
#
# SPDX-License-Identifier: MIT
"""Support module for the LifeScan binary protocol.
A number of LifeScan devices use a semi-compatible binary protocol to talk host
and device, which is (vastly) compatible.
This module implements an interface to send and receive these messages.
"""
import construct
from glucometerutils import common
from glucometerutils.support import construct_extras, lifescan
_LINK_CONTROL = construct.BitStruct(
construct.Padding(3),
"more" / construct.Default(construct.Flag, False),
"disconnect" / construct.Default(construct.Flag, False),
"acknowledge" / construct.Default(construct.Flag, False),
"expect_receive" / construct.Default(construct.Flag, False),
"sequence_number" / construct.Default(construct.Flag, False),
)
def LifeScanPacket(include_link_control): # pylint: disable=invalid-name
# type: (bool) -> construct.Struct
if include_link_control:
link_control_construct = _LINK_CONTROL
else:
link_control_construct = construct.Const(b"\x00")
return construct.Struct(
"data"
/ construct.RawCopy(
construct.Struct(
construct.Const(b"\x02"), # stx
"length"
/ construct.Rebuild(construct.Byte, lambda this: len(this.message) + 6),
"link_control" / link_control_construct,
"message" / construct.Bytes(lambda this: this.length - 6),
construct.Const(b"\x03"), # etx
),
),
"checksum"
/ construct.Checksum(
construct.Int16ul, lifescan.crc_ccitt, construct.this.data.data
),
)
VERIO_TIMESTAMP = construct_extras.Timestamp(
construct.Int32ul, epoch=946684800
) # 2000-01-01 (not 2010)
_GLUCOSE_UNIT_MAPPING_TABLE = {
common.Unit.MG_DL: 0x00,
common.Unit.MMOL_L: 0x01,
}
GLUCOSE_UNIT = construct.Mapping(construct.Byte, _GLUCOSE_UNIT_MAPPING_TABLE)
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