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#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# Copyright 2018 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
import pmt
from . import hdlc_deframer
from . import hdlc
class k2sat_deframer(gr.basic_block):
"""docstring for block k2sat_deframer"""
def __init__(self):
gr.basic_block.__init__(
self,
name='k2sat_deframer',
in_sig=[],
out_sig=[])
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'))
self.number = 0
# CRC-16 table construction
self.crc_table = list()
for i in range(256):
tmp = 0
if i & 1:
tmp ^= 0x1021
if i & 2:
tmp ^= 0x2042
if i & 4:
tmp ^= 0x4084
if i & 8:
tmp ^= 0x8108
if i & 16:
tmp ^= 0x1231
if i & 32:
tmp ^= 0x2462
if i & 64:
tmp ^= 0x48C4
if i & 128:
tmp ^= 0x9188
self.crc_table.append(tmp)
def check_packet(self, packet):
data = b'\x7e' + packet # add 0x7e HDLC flag for CRC-16 check
checksum = 0xFFFF
for d in data:
checksum = (((checksum << 8) & 0xFF00)
^ self.crc_table[((checksum >> 8) ^ d) & 0x00FF])
return checksum == 0
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
packet = bytes(pmt.u8vector_elements(msg))
# Search all packet end markers in current packet
start = 0
while True:
# Find packet end marker
idx = packet[start:].find(b'\x7e\x55\x55\x55')
if idx == -1:
break
# Check if this is a valid packet
if self.check_packet(packet[:idx]):
ax25_packet = packet[:-2+idx]
ax25_packet = list(packet) # conversion to list for pybind11
self.message_port_pub(
pmt.intern('out'),
pmt.cons(pmt.PMT_NIL,
pmt.init_u8vector(len(ax25_packet), ax25_packet)))
start = idx + 2
return
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