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# -*- coding: utf-8 -*-
"""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.
"""
__author__ = 'Diego Elio Pettenò'
__email__ = 'flameeyes@flameeyes.eu'
__copyright__ = 'Copyright © 2014-2018, Diego Elio Pettenò'
__license__ = 'MIT'
import construct
from glucometerutils import common
from glucometerutils.support import construct_extras
from glucometerutils.support import 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(command_prefix, include_link_control):
if include_link_control:
link_control_construct = _LINK_CONTROL
else:
link_control_construct = construct.Const(b'\x00')
command_prefix_construct = construct.Const(command_prefix, construct.Byte)
return construct.Struct(
construct.RawCopy(
construct.Embedded(
construct.Struct(
construct.Const(b'\x02'), # stx
'length' / construct.Rebuild(
construct.Byte, lambda ctx: len(ctx.message) + 7),
'link_control' / link_control_construct,
'command_prefix' / command_prefix_construct,
'message' / construct.Bytes(
length=lambda ctx: ctx.length - 7),
construct.Const(b'\x03'), # etx
),
),
),
'checksum' / construct.Checksum(
construct.Int16ul, lifescan.crc_ccitt, construct.this.data),
)
COMMAND_SUCCESS = construct.Const(b'\x06')
VERIO_TIMESTAMP = construct_extras.Timestamp(
construct.Int32ul, epoch=946684800) # 2010-01-01 00:00
_GLUCOSE_UNIT_MAPPING_TABLE = {
common.Unit.MG_DL: 0x00,
common.Unit.MMOL_L: 0x01,
}
GLUCOSE_UNIT = construct.SymmetricMapping(
construct.Byte, _GLUCOSE_UNIT_MAPPING_TABLE)
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