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#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# Copyright 2019 Daniel Estevez <daniel@destevez.net>
#
# This file is part of gr-satellites
#
# SPDX-License-Identifier: GPL-3.0-or-later
#
from gnuradio import gr, blocks, digital, fec
from ... import decode_rs, aausat4_remove_fsm
from ...grpdu import pdu_to_tagged_stream, tagged_stream_to_pdu
from ...grtypes import byte_t
from ...hier.sync_to_pdu_soft import sync_to_pdu_soft
from ...hier.ccsds_descrambler import ccsds_descrambler
from ...utils.options_block import options_block
_syncword = '010011110101101000110100010000110101010101000010'
class aausat4_deframer(gr.hier_block2, options_block):
"""
Hierarchical block to deframe AAUSAT-4 frames
These frames use a terminated CCSDS convolutional code, a
CCSDS scrambler and CCSDS Reed-Solomon.
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,
'aausat4_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.deframer = sync_to_pdu_soft(
packlen=1996 + 8, sync=_syncword, threshold=syncword_threshold)
self.fsm = aausat4_remove_fsm()
self.viterbi_short = fec.cc_decoder.make(
1020, 7, 2, [79, -109], 0, -1, fec.CC_TERMINATED, False)
self.viterbi_decoder_short = fec.async_decoder(
self.viterbi_short, True, False, 1020//8)
self.viterbi_long = fec.cc_decoder.make(
1996, 7, 2, [79, -109], 0, -1, fec.CC_TERMINATED, False)
self.viterbi_decoder_long = fec.async_decoder(
self.viterbi_long, False, False, 1996//8)
# Workaround for bug https://github.com/gnuradio/gnuradio/pull/2965
# We use packed output for Viterbi short decoder and then
# we unpack the PDUs.
self.pdu2tag = pdu_to_tagged_stream(byte_t, 'packet_len')
self.unpack = blocks.packed_to_unpacked_bb(1, gr.GR_MSB_FIRST)
self.taglength = blocks.tagged_stream_multiply_length(
gr.sizeof_char*1, 'packet_len', 8)
self.tag2pdu = tagged_stream_to_pdu(byte_t, 'packet_len')
self.scrambler = ccsds_descrambler()
self.rs = decode_rs(False, 1)
self.connect(self, self.deframer)
self.msg_connect((self.deframer, 'out'), (self.fsm, 'in'))
self.msg_connect((self.fsm, 'short'),
(self.viterbi_decoder_short, 'in'))
self.msg_connect((self.fsm, 'long'), (self.viterbi_decoder_long, 'in'))
# Workaround
self.msg_connect((self.viterbi_decoder_short, 'out'),
(self.pdu2tag, 'pdus'))
self.connect(self.pdu2tag, self.unpack, self.taglength, self.tag2pdu)
self.msg_connect((self.tag2pdu, 'pdus'), (self.scrambler, 'in'))
self.msg_connect((self.viterbi_decoder_long, 'out'),
(self.scrambler, 'in'))
self.msg_connect((self.scrambler, 'out'), (self.rs, 'in'))
self.msg_connect((self.rs, 'out'), (self, 'out'))
_default_sync_threshold = 8
@classmethod
def add_options(cls, parser):
"""
Adds AAUSAT-4 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]')
parser.add_argument(
'--verbose_rs', action='store_true', help='Verbose RS decoder')
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