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# Copyright (c) 2015, Nordic Semiconductor
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# * Redistributions of source code must retain the above copyright notice, this
# list of conditions and the following disclaimer.
#
# * Redistributions in binary form must reproduce the above copyright notice,
# this list of conditions and the following disclaimer in the documentation
# and/or other materials provided with the distribution.
#
# * Neither the name of Nordic Semiconductor ASA nor the names of its
# contributors may be used to endorse or promote products derived from
# this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
UART_HEADER_OCTET_COUNT = 4
class ThreeWireUartPacket(object):
"""
This class encapsulate a three wire uart packet according to Bluetooth specification
version 4.0 [Vol 4] part D.
"""
def __init__(self):
self.ack = None # Acknowledgement number
self.seq = None # Sequence number
self.di = None # Data integrity present
self.rp = None # Reliable packet
self.type = None # Packet type
self.length = None # Payload Length
self.checksum = None # Header checksum
self.payload = None # Payload
@staticmethod
def decode(packet):
"""
Decodes a packet from a str encoded array
:param packet_bytes: A str encoded array
:return: TheeWireUartPacket
"""
decoded_packet = ThreeWireUartPacket()
packet_bytes = bytearray(packet)
decoded_packet.ack = (packet_bytes[0] & int('38', 16)) >> 3
decoded_packet.seq = (packet_bytes[0] & int('07', 16))
decoded_packet.di = (packet_bytes[0] & int('40', 16)) >> 6
decoded_packet.rp = (packet_bytes[0] & int('80', 16)) >> 7
decoded_packet.type = (packet_bytes[1] & int('0F', 16))
decoded_packet.length = ((packet_bytes[1] & int('F0', 16)) >> 4) + (packet_bytes[2] * 16)
checksum = packet_bytes[0]
checksum = checksum + packet_bytes[1]
checksum = checksum + packet_bytes[2]
checksum &= int('FF', 16)
decoded_packet.checksum = (~checksum + 1) & int('FF', 16)
if decoded_packet.length > 0:
decoded_packet.payload = packet_bytes[UART_HEADER_OCTET_COUNT:-1]
return decoded_packet
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