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#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# Copyright 2018,2020 Daniel Estevez <daniel@destevez.net>
#
# This file is part of gr-satellites
#
# SPDX-License-Identifier: GPL-3.0-or-later
#
from gnuradio import gr
import numpy as np
import pmt
from .bch15 import decode_bch15
from .telemetry.snet import LTUFrameHeader
class snet_deframer(gr.basic_block):
"""docstring for block snet_deframer"""
def __init__(self, verbose=False, buggy_crc=True):
gr.basic_block.__init__(
self,
name='snet_deframer',
in_sig=[],
out_sig=[])
self.verbose = verbose
self.buggy_crc = buggy_crc
self.message_port_register_in(pmt.intern('in'))
self.set_msg_handler(pmt.intern('in'), self.handle_msg)
self.message_port_register_out(pmt.intern('out'))
def handle_msg(self, msg_pmt):
msg = pmt.cdr(msg_pmt)
if not pmt.is_u8vector(msg):
print('[ERROR] Received invalid message type. Expected u8vector')
return
bits = np.array(pmt.u8vector_elements(msg))
ltu = bits[:210].reshape((15, 14)).transpose()
# Decode BCH(15,5,7)
if not all((decode_bch15(ltu[j, :]) for j in range(14))):
# Decode failure
if self.verbose:
print('BCH decode failure')
return
ltu = np.fliplr(ltu[:, -5:]).ravel()
hdr = LTUFrameHeader.parse(np.packbits(ltu))
ltu_crc = np.concatenate((ltu[:-5], np.array([1, 0, 1, 1, 0, 1, 1])))
ltu_crc = ltu_crc.reshape((9, 8))
if self.buggy_crc:
# Reverse byte ordering for CRC5 calculation
ltu_crc = np.flipud(ltu_crc)
if self.buggy_crc:
# Force CRC5 bugs
ltu_crc[4, :] = ltu_crc[3, :]
# CRC5 calculation
crc = 0x1F
for bit in ltu_crc.ravel():
# Check most significant bit in the CRC buffer and save
# in a variable.
c = crc & 0x10
# Shift variable to make the compare op. possible (see beneath).
c >>= 4
# Shift CRC to the left and write 0 into the least significant bit.
crc <<= 1
if c != bit:
crc ^= 0x15 # CRC polynomial
crc &= 0x1F
if crc != hdr.CRC5:
if self.verbose:
print('CRC5 fail')
return
if self.verbose:
print(hdr)
if hdr.PduLength == 0:
return
codewords_per_block = 16
uncoded = False
if hdr.AiTypeSrc == 0:
uncoded = True
elif hdr.AiTypeSrc == 1:
data_bits_per_codeword = 11 # BCH(15,11,3)
bch_d = 3
elif hdr.AiTypeSrc == 2:
data_bits_per_codeword = 7 # BCH(15,7,5)
bch_d = 5
elif hdr.AiTypeSrc == 3:
data_bits_per_codeword = 5 # BCH(15,5,7)
bch_d = 7
else:
if self.verbose:
print('Invalid AiTypeSrc')
return
if uncoded:
pdu_bytes = bits[210:210+hdr.PduLength*8]
pdu_bytes = pdu_bytes.reshape((hdr.PduLength, 8))
pdu_bytes = np.fliplr(pdu_bytes)
else:
data_bytes_per_block = (codewords_per_block
* data_bits_per_codeword // 8)
num_blocks = int(np.ceil(float(
hdr.PduLength) / data_bytes_per_block))
blocks = list()
for k in range(num_blocks):
block = bits[210+k*16*15:210+(k+1)*16*15].reshape((15, 16))
if bch_d:
block = block.transpose()
if not bch_d:
print(block)
# Decode BCH
if (bch_d
and not all((decode_bch15(block[j, :], d=bch_d)
for j in range(16)))):
# Decode failure
if self.verbose:
print('BCH decode failure')
return
if bch_d:
blocks.append(block[:, -data_bits_per_codeword:].ravel())
else:
blocks.append(block.ravel())
pdu_bytes = np.concatenate(blocks)
pdu_bytes = pdu_bytes.reshape((data_bytes_per_block
* num_blocks, 8))
pdu_bytes = np.fliplr(pdu_bytes)
# Drop 0xDB padding bytes at the end
pdu_bytes = pdu_bytes[:hdr.PduLength]
if not bch_d:
print(pdu_bytes)
# CRC13
crc = 0x1FFF
pdu_crc = np.flipud(pdu_bytes) if self.buggy_crc else pdu_bytes
for bit in pdu_crc.ravel():
# Check most significant bit in the CRC buffer and save it
# in a variable.
c = crc & 0x1000
# Shift variable to make the compare op. possible (see beneath).
c >>= 12
# Shift CRC to the left and write 0 into the least significant bit.
crc <<= 1
if (c or bit if self.buggy_crc else c != bit):
crc ^= 0x1CF5 # CRC polynomial
crc &= 0x1FFF
if crc != hdr.CRC13:
if self.verbose:
print('CRC13 fail')
return
pdu = np.packbits(pdu_bytes)
pdu_tags = pmt.make_dict()
pdu_tags = pmt.dict_add(
pdu_tags, pmt.intern('SNET SrcId'), pmt.from_long(hdr.SrcId))
self.message_port_pub(
pmt.intern('out'),
pmt.cons(pdu_tags, pmt.init_u8vector(len(pdu), pdu)))
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