Ryan Malloy
5867c54de3
Ported from zleffke/gr-sarsat (2018, GNU Radio 3.7): - Updated Python 2 → Python 3 - Converted XML block definitions to YAML - Added pyproject.toml for modern packaging - Preserved original MIT license Blocks: - biphase_l_decode_bb: Manchester decoder (decim_block) - pds_frame_sync: Frame synchronizer with PDU output - sarp_msg_extract: SARP message splitter/validator
84 lines
2.7 KiB
Python
84 lines
2.7 KiB
Python
#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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# MIT License
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# Copyright (c) 2018 zleffke
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# Ported to GNU Radio 3.10+ by gr-mcp
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"""
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SARP (Search And Rescue Processor) Message Extractor.
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Each 72-byte PDS frame contains three 24-byte SARP messages.
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Each SARP message starts with a 12-bit sync word: 0xD60
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This block:
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1. Receives PDS frame PDUs
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2. Splits into three 24-byte SARP messages
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3. Validates sync word (0xD60)
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4. Routes to 'valid' or 'invalid' output port
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"""
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import numpy as np
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import pmt
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import binascii
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from gnuradio import gr
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class sarp_msg_extract(gr.basic_block):
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"""
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SARP Message Extractor.
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Input: PDU from PDS Frame Sync Block (72 bytes)
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Output: Individual SARP messages (24 bytes each) on 'valid' or 'invalid' ports
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A SARP message is considered valid if its sync word matches 0xD60.
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Even invalid messages may contain recoverable beacon data via BCH codes.
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"""
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def __init__(self):
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gr.basic_block.__init__(
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self,
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name="sarp_msg_extract",
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in_sig=None,
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out_sig=None,
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)
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self.message_port_register_in(pmt.intern("in"))
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self.set_msg_handler(pmt.intern("in"), self.handle_msg)
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self.message_port_register_out(pmt.intern("valid"))
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self.message_port_register_out(pmt.intern("invalid"))
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def _check_sync_word(self, msg: bytearray) -> bool:
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"""Check if SARP message has valid sync word (0xD60)."""
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# Sync word is first 12 bits: 0xD6 followed by upper nibble 0x0
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return (msg[0] == 0xD6) and ((msg[1] & 0xF0) == 0x00)
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def _publish_msg(self, msg: bytearray, valid: bool):
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"""Publish SARP message to appropriate output port."""
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port = "valid" if valid else "invalid"
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pdu = pmt.cons(pmt.PMT_NIL, pmt.init_u8vector(len(msg), msg))
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self.message_port_pub(pmt.intern(port), pdu)
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def handle_msg(self, msg_pmt):
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"""Process incoming PDS frame PDU."""
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pds_msg = pmt.cdr(msg_pmt)
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if not pmt.is_u8vector(pds_msg):
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print("[ERROR] Received invalid message type. Expected u8vector")
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return
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buff = bytearray(pmt.u8vector_elements(pds_msg))
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if len(buff) < 72:
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print(f"[ERROR] PDS frame too short: {len(buff)} bytes (expected 72)")
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return
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# Extract three 24-byte SARP messages
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sarp_msg_1 = bytearray(buff[0:24])
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sarp_msg_2 = bytearray(buff[24:48])
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sarp_msg_3 = bytearray(buff[48:72])
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# Validate and publish each message
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self._publish_msg(sarp_msg_1, self._check_sync_word(sarp_msg_1))
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self._publish_msg(sarp_msg_2, self._check_sync_word(sarp_msg_2))
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self._publish_msg(sarp_msg_3, self._check_sync_word(sarp_msg_3))
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