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#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# Copyright 2017 Daniel Estevez <daniel@destevez.net>
#
# This file is part of gr-satellites
#
# SPDX-License-Identifier: GPL-3.0-or-later
#
import struct
from gnuradio import gr
import numpy
import pmt
class check_address(gr.basic_block):
"""docstring for block check_address"""
def __init__(self, address, direction, digicallsign=''):
gr.basic_block.__init__(
self,
name='check_address',
in_sig=[],
out_sig=[])
a = address.rsplit('-', 1)
self.callsign = a[0]
self.ssid = int(a[1]) if len(a) > 1 else None
self.direction = direction
self.digicallsign = digicallsign
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('ok'))
self.message_port_register_out(pmt.intern('fail'))
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))
# Check packet length.
# An AX.25 header with 2 addresses, control and PID is 16 bytes.
if len(packet) < 16:
self.message_port_pub(pmt.intern('fail'), msg_pmt)
return
if self.direction == 'to':
address = packet[:7]
else:
address = packet[7:14]
hbit = 0
if len(packet) > 20:
hbit = packet[20] >> 7
# digi callsign; and above: hbit (most significant bit after digi callsign)
# (set to 1 in case of digipeated message)
digi = [c >> 1 for c in packet[14:20]]
digi = bytes(digi).decode('ascii').rstrip(' ')
# extension bit (least significant bit after sender callsign)
# (set to 0 in case of digi callsign follows)
ebit = packet[13] & 0x01
callsign = [c >> 1 for c in address[:6]]
callsign = bytes(callsign).decode('ascii').rstrip(' ')
ssid = (address[6] >> 1) & 0x0f
# altered if sentence
if ((callsign == self.callsign
and (self.ssid is None or ssid == self.ssid))
or (ebit == 0 and hbit == 1 and digi == self.digicallsign)):
# match
self.message_port_pub(pmt.intern('ok'), msg_pmt)
else:
# no match
self.message_port_pub(pmt.intern('fail'), msg_pmt)
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