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# Copyright 2025 Fabian P. Schmidt <kerel@mailbox.org>
#
# This file is part of gr-satellites
#
# SPDX-License-Identifier: GPL-3.0-or-later
import sys
from gnuradio import gr
import pmt
from .mobitex_fec import decode, Status, unpack_2b
class mobitex_fec(gr.basic_block):
"""
Block to perform error-correction on Mobitex data blocks.
# Input
PDU with encoded Mobitex data block (20 * 12 bits)
# Output
PDU with decoded Mobitex data block (20 * 8 bits)
Output Tags:
- corrected_errors (int): Number of corrected bit errors
- uncorrected_errors (int): Number of uncorrectable bit errors
"""
def __init__(self):
gr.basic_block.__init__(
self,
name='mobitex_fec',
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'))
def handle_msg(self, msg_pmt):
meta = pmt.car(msg_pmt)
msg = pmt.cdr(msg_pmt)
if not pmt.is_u8vector(msg):
print('[ERROR] Received invalid message type. Expected u8vector')
return
block = pmt.u8vector_elements(msg)
if len(block) != 30:
print(
'[ERROR] Received invalid Mobitex data block, '
f'expected 30 bytes (got {len(block)} bytes).'
)
return
triplets = (block[a:a + 3] for a in range(0, len(block), 3))
codewords = [codeword for triplet in triplets
for codeword in unpack_2b(bytes(triplet))]
packet_out = []
errors_corrected = 0
errors_uncorrected = 0
for codeword in codewords:
corrected, _, status = decode(codeword)
packet_out.append(corrected)
if status == Status.NO_ERROR:
pass
elif status == Status.ERROR_CORRECTED:
errors_corrected += 1
elif status == Status.ERROR_UNCORRECTABLE:
errors_uncorrected += 1
meta = pmt.dict_add(
meta,
pmt.intern('corrected_errors'),
pmt.from_long(errors_corrected),
)
meta = pmt.dict_add(
meta,
pmt.intern('uncorrected_errors'),
pmt.from_long(errors_uncorrected),
)
self.message_port_pub(
pmt.intern('out'),
pmt.cons(meta, pmt.init_u8vector(len(packet_out), packet_out)))
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