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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
#
import numpy as np
from gnuradio import gr
import pmt
# Details of the NGHam protocol taken from
# https://github.com/skagmo/ngham/blob/master/ngham.c
_tags = [
0b001110110100100111001101,
0b010011011101101001010111,
0b011101101001001110011010,
0b100110111011010010101110,
0b101000001111110101100011,
0b110101100110111011111001,
0b111011010010011100110100]
ngham_tags = np.array([list(map(int, ('0'*24 + bin(t)[2:])[-24:]))
for t in _tags],
dtype='uint8')
ngham_rs_sizes = [47, 79, 111, 159, 191, 223, 255]
class ngham_packet_crop(gr.basic_block):
"""
Crops an NGHam packet according to its size tag
Input: An NGHam packet with size tag and RS codeword
Output: The RS codeword appropriately cropped, routed to
rs16 or rs32 according to the RS parity check bytes
"""
def __init__(self):
gr.basic_block.__init__(
self,
name='ngham_packet_handler',
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('rs16'))
self.message_port_register_out(pmt.intern('rs32'))
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 = pmt.u8vector_elements(msg)
size_tag = np.unpackbits(np.array(packet[:3], dtype='uint8'))
tag_dist = np.sum(size_tag ^ ngham_tags, axis=1)
best_tag = np.argmin(tag_dist)
rs_size = ngham_rs_sizes[best_tag]
if len(packet[3:]) < rs_size:
print('Packet is too short')
return
out = 'rs16' if best_tag < 3 else 'rs32'
self.message_port_pub(
pmt.intern(out),
pmt.cons(pmt.car(msg_pmt),
pmt.init_u8vector(rs_size, packet[3:3+rs_size])))
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