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#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# Copyright 2019, 2022 Daniel Estevez <daniel@destevez.net>
#
# This file is part of gr-satellites
#
# SPDX-License-Identifier: GPL-3.0-or-later
#
from gnuradio import gr, digital
from ...crcs import crc16_ccitt_false
from ...hier.sync_to_pdu_packed import sync_to_pdu_packed
from ...utils.options_block import options_block
_syncword = '00111001000101011110110100110000'
class ao40_uncoded_deframer(gr.hier_block2, options_block):
"""
Hierarchical block to deframe the AO-40 uncoded framing.
The input is a float stream of soft symbols. The output are PDUs
with frames.
Args:
syncword_threshold: number of bit errors allowed in syncword (int)
options: Options from argparse
"""
def __init__(self, syncword_threshold=None, options=None):
gr.hier_block2.__init__(
self,
'ao40_uncoded_deframer',
gr.io_signature(1, 1, gr.sizeof_float),
gr.io_signature(0, 0, 0))
options_block.__init__(self, options)
self.message_port_register_hier_out('out')
if syncword_threshold is None:
syncword_threshold = self.options.syncword_threshold
self.slicer = digital.binary_slicer_fb()
self.deframer = sync_to_pdu_packed(
packlen=512 + 2, sync=_syncword, threshold=syncword_threshold)
self.crc = crc16_ccitt_false()
self.connect(self, self.slicer, self.deframer)
self.msg_connect((self.deframer, 'out'), (self.crc, 'in'))
self.msg_connect((self.crc, 'ok'), (self, 'out'))
_default_sync_threshold = 3
@classmethod
def add_options(cls, parser):
"""
Adds AO-40 uncoded deframer specific options to the argparse parser
"""
parser.add_argument(
'--syncword_threshold', type=int,
default=cls._default_sync_threshold,
help='Syncword bit errors [default=%(default)r]')
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