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111 lines
4.0 KiB
111 lines
4.0 KiB
/* AO40 encoder / decoder
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* Copyright 2002 Phil Karn, KA9Q
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* May be used under the terms of the GNU General Public License (GPL)
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* See CodecAO40.cpp for lineage
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*
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* This file is part of FUNcubeLib.
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*
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* FUNcubeLib is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* FUNcubeLib is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with FUNcubeLib If not, see <http://www.gnu.org/licenses/>.
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*
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*/
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#pragma once
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//#include "fecConstants.h"
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/*
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Amsat P3 FEC Encoder/decoder system. Look-up tables
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Created by Phil Karn KA9Q and James Miller G3RUH
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Last modified 2003 Jun 20
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*/
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/* Defines for Viterbi Decoder for r=1/2 k=7 (to CCSDS convention) */
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#define K 7 /* Constraint length */
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#define N 2 /* Number of symbols per data bit */
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#define CPOLYA 0x4f /* First convolutional encoder polynomial */
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#define CPOLYB 0x6d /* Second convolutional encoder polynomial */
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#define SYNC_POLY 0x48 /* Sync vector PN polynomial */
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#define NN 255
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#define KK 223
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#define NROOTS 32 /* NN-KK */
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#define A0 (NN)
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#define FCR 112
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#define PRIM 11
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#define IPRIM 116
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#define BLOCKSIZE 256 /* Data bytes per frame */
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#define RSBLOCKS 2 /* Number of RS decoder blocks */
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#define RSPAD 95 /* Unused bytes in block (KK-BLOCKSIZE/RSBLOCKS) */
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/* Defines for Interleaver */
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#define ROWS 80 /* Block interleaver rows */
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#define COLUMNS 65 /* Block interleaver columns */
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#define SYMPBLOCK (ROWS*COLUMNS) /* Encoded symbols per block */
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/* Number of symbols in an FEC block that are */
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/* passed to the Viterbi decoder (320*8 + 6) */
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#define NBITS ((BLOCKSIZE+NROOTS*RSBLOCKS)*8+K-1)
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/* Number of bits obtained from Viterbi decoder */
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#define NBITS_OUT (BLOCKSIZE+NROOTS*RSBLOCKS)
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extern unsigned char m_RS_block[RSBLOCKS][NROOTS]; /* RS parity blocks */
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extern unsigned char m_encoded[SYMPBLOCK] ; /* encoded symbols */
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extern int m_encoded_bytes; /* Byte counter for encode_data() */
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extern int m_ileaver_index; /* Byte counter for interleaver */
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extern unsigned char m_conv_sr; /* Convolutional encoder shift register state */
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extern const unsigned char RS_poly[];
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extern const unsigned char ALPHA_TO[];
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extern const unsigned char INDEX_OF[];
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extern const unsigned char Partab[];
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extern const unsigned char Scrambler[];
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//class CCodecAO40
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//{
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//public:
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// CCodecAO40(void);
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// virtual ~CCodecAO40(void);
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int decode(unsigned char viterbi_decoded[NBITS_OUT], unsigned char *decoded_data);
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/* Encodes the 256 byte source block into 5200 byte block of symbols into m_encoded buffer */
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const unsigned char *encode(
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unsigned char *source_bytes, /* input to encode */
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int byte_count); /* input length in bytes */
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/* Compares raw input symbols to current buffer of encoded symbols and counts the errors */
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int count_errors( unsigned char *raw_symbols);
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//private:
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int mod255(int x);
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int decode_rs_8(char *data, int *eras_pos, int no_eras);
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void scramble_and_encode(unsigned char c);
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void encode_and_interleave(unsigned char c,int cnt);
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void descramble_to_rsblocks(
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unsigned char viterbi_decoded[NBITS_OUT],
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char rsblocks[RSBLOCKS][NN]);
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void init_encoder(void);
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void encode_byte(unsigned char c);
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void encode_parity(void);
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void interleave_symbol(int c);
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//};
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