mirror of
https://github.com/M17-Project/libm17
synced 2026-08-08 12:32:03 -04:00
0ee873c82b
- headers cleanup - API change - callsign decode/encode functions use `char*` now - fixed how unit tests are built
352 lines
11 KiB
C
Executable file
352 lines
11 KiB
C
Executable file
//--------------------------------------------------------------------
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// M17 C library - m17.c
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//
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// Wojciech Kaczmarski, SP5WWP
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// M17 Foundation, 12 March 2025
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//--------------------------------------------------------------------
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#include <string.h>
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#include "m17.h"
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__attribute__((visibility("default")))
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const char libm17_version[] = LIBM17_VERSION;
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/**
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* @brief Generate symbol stream for a preamble.
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*
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* @param out Frame buffer (192 floats).
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* @param cnt Pointer to a variable holding the number of written symbols.
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* @param type Preamble type (pre-BERT or pre-LSF).
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*/
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void gen_preamble(float out[SYM_PER_FRA], uint32_t *cnt, const pream_t type)
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{
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if(type==PREAM_BERT) //pre-BERT
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{
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for(uint16_t i=0; i<SYM_PER_FRA/2; i++) //40ms * 4800 = 192
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{
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out[(*cnt)++]=-3.0;
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out[(*cnt)++]=+3.0;
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}
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}
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else// if(type==PREAM_LSF) //pre-LSF
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{
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for(uint16_t i=0; i<SYM_PER_FRA/2; i++) //40ms * 4800 = 192
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{
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out[(*cnt)++]=+3.0;
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out[(*cnt)++]=-3.0;
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}
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}
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}
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/**
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* @brief Generate symbol stream for a preamble.
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*
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* @param out Frame buffer (192 int8_t).
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* @param cnt Pointer to a variable holding the number of written symbols.
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* @param type Preamble type (pre-BERT or pre-LSF).
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*/
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void gen_preamble_i8(int8_t out[SYM_PER_FRA], uint32_t *cnt, const pream_t type)
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{
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if(type==PREAM_BERT) //pre-BERT
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{
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for(uint16_t i=0; i<SYM_PER_FRA/2; i++) //40ms * 4800 = 192
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{
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out[(*cnt)++]=-3;
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out[(*cnt)++]=+3;
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}
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}
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else// if(type==PREAM_LSF) //pre-LSF
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{
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for(uint16_t i=0; i<SYM_PER_FRA/2; i++) //40ms * 4800 = 192
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{
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out[(*cnt)++]=+3;
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out[(*cnt)++]=-3;
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}
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}
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}
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/**
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* @brief Generate symbol stream for a syncword.
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*
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* @param out Output buffer (8 floats).
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* @param cnt Pointer to a variable holding the number of written symbols.
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* @param syncword Syncword.
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*/
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void gen_syncword(float out[SYM_PER_SWD], uint32_t *cnt, const uint16_t syncword)
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{
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for(uint8_t i=0; i<SYM_PER_SWD*2; i+=2)
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{
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out[(*cnt)++]=symbol_map[(syncword>>(14-i))&3];
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}
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}
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/**
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* @brief Generate symbol stream for a syncword.
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*
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* @param out Output buffer (8 int8_t).
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* @param cnt Pointer to a variable holding the number of written symbols.
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* @param syncword Syncword.
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*/
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void gen_syncword_i8(int8_t out[SYM_PER_SWD], uint32_t *cnt, const uint16_t syncword)
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{
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for(uint8_t i=0; i<SYM_PER_SWD*2; i+=2)
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{
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out[(*cnt)++]=symbol_map[(syncword>>(14-i))&3];
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}
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}
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/**
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* @brief Generate symbol stream for frame contents (without the syncword).
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* Can be used for both LSF and data frames.
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*
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* @param out Output buffer (184 floats).
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* @param cnt Pointer to a variable holding the number of written symbols.
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* @param in Data input - unpacked bits (1 bit per byte).
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*/
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void gen_data(float out[SYM_PER_PLD], uint32_t *cnt, const uint8_t* in)
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{
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for(uint16_t i=0; i<SYM_PER_PLD; i++) //40ms * 4800 - 8 (syncword)
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{
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out[(*cnt)++]=symbol_map[in[2*i]*2+in[2*i+1]];
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}
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}
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/**
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* @brief Generate symbol stream for frame contents (without the syncword).
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* Can be used for both LSF and data frames.
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*
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* @param out Output buffer (184 int8_t).
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* @param cnt Pointer to a variable holding the number of written symbols.
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* @param in Data input - unpacked bits (1 bit per byte).
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*/
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void gen_data_i8(int8_t out[SYM_PER_PLD], uint32_t *cnt, const uint8_t* in)
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{
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for(uint16_t i=0; i<SYM_PER_PLD; i++) //40ms * 4800 - 8 (syncword)
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{
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out[(*cnt)++]=symbol_map[in[2*i]*2+in[2*i+1]];
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}
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}
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/**
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* @brief Generate symbol stream for the End of Transmission marker.
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*
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* @param out Output buffer (192 floats).
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* @param cnt Pointer to a variable holding the number of written symbols.
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*/
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void gen_eot(float out[SYM_PER_FRA], uint32_t *cnt)
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{
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for(uint16_t i=0; i<SYM_PER_FRA; i++) //40ms * 4800 = 192
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{
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out[(*cnt)++]=eot_symbols[i%8];
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}
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}
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/**
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* @brief Generate symbol stream for the End of Transmission marker.
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*
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* @param out Output buffer (192 int8_t).
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* @param cnt Pointer to a variable holding the number of written symbols.
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*/
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void gen_eot_i8(int8_t out[SYM_PER_FRA], uint32_t *cnt)
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{
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for(uint16_t i=0; i<SYM_PER_FRA; i++) //40ms * 4800 = 192
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{
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out[(*cnt)++]=eot_symbols[i%8];
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}
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}
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/**
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* @brief Generate frame symbols.
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*
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* @param out Output buffer for symbols (192 floats).
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* @param data Payload (16 or 25 bytes).
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* @param type Frame type (LSF, Stream, Packet).
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* @param lsf Pointer to a structure holding Link Setup Frame data.
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* @param lich_cnt LICH counter (0..5).
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* @param fn Frame number.
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*/
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void gen_frame(float out[SYM_PER_FRA], const uint8_t* data, const frame_t type, const lsf_t* lsf, const uint8_t lich_cnt, const uint16_t fn)
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{
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uint8_t lich[6]; //48 bits packed raw, unencoded LICH
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uint8_t lich_encoded[12]; //96 bits packed, encoded LICH
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uint8_t enc_bits[SYM_PER_PLD*2]; //type-2 bits, unpacked
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uint8_t rf_bits[SYM_PER_PLD*2]; //type-4 bits, unpacked
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uint32_t sym_cnt=0; //symbols written counter
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if(type==FRAME_LSF)
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{
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gen_syncword(out, &sym_cnt, SYNC_LSF);
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conv_encode_LSF(enc_bits, lsf);
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}
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else if(type==FRAME_STR)
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{
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gen_syncword(out, &sym_cnt, SYNC_STR);
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extract_LICH(lich, lich_cnt, lsf);
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encode_LICH(lich_encoded, lich);
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unpack_LICH(enc_bits, lich_encoded);
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conv_encode_stream_frame(&enc_bits[96], data, fn); //stream frames require 16-byte payloads
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}
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else if(type==FRAME_PKT)
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{
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gen_syncword(out, &sym_cnt, SYNC_PKT);
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conv_encode_packet_frame(enc_bits, data); //packet frames require 200-bit payload chunks plus a 6-bit counter
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}
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else if(type==FRAME_BERT)
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{
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gen_syncword(out, &sym_cnt, SYNC_BER);
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conv_encode_bert_frame(enc_bits, data); //BERT frames require 197 BERT bits packed as 25 bytes
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}
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//common stuff
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reorder_bits(rf_bits, enc_bits);
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randomize_bits(rf_bits);
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gen_data(out, &sym_cnt, rf_bits);
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}
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/**
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* @brief Generate frame symbols.
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*
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* @param out Output buffer for symbols (192 int8_t).
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* @param data Payload (16 or 25 bytes).
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* @param type Frame type (LSF, Stream, Packet).
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* @param lsf Pointer to a structure holding Link Setup Frame data.
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* @param lich_cnt LICH counter (0..5).
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* @param fn Frame number.
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*/
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void gen_frame_i8(int8_t out[SYM_PER_FRA], const uint8_t* data, const frame_t type, const lsf_t* lsf, const uint8_t lich_cnt, const uint16_t fn)
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{
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uint8_t lich[6]; //48 bits packed raw, unencoded LICH
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uint8_t lich_encoded[12]; //96 bits packed, encoded LICH
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uint8_t enc_bits[SYM_PER_PLD*2]; //type-2 bits, unpacked
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uint8_t rf_bits[SYM_PER_PLD*2]; //type-4 bits, unpacked
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uint32_t sym_cnt=0; //symbols written counter
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if(type==FRAME_LSF)
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{
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gen_syncword_i8(out, &sym_cnt, SYNC_LSF);
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conv_encode_LSF(enc_bits, lsf);
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}
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else if(type==FRAME_STR)
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{
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gen_syncword_i8(out, &sym_cnt, SYNC_STR);
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extract_LICH(lich, lich_cnt, lsf);
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encode_LICH(lich_encoded, lich);
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unpack_LICH(enc_bits, lich_encoded);
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conv_encode_stream_frame(&enc_bits[96], data, fn); //stream frames require 16-byte payloads
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}
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else if(type==FRAME_PKT)
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{
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gen_syncword_i8(out, &sym_cnt, SYNC_PKT);
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conv_encode_packet_frame(enc_bits, data); //packet frames require 200-bit payload chunks plus a 6-bit counter
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}
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else if(type==FRAME_BERT)
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{
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gen_syncword_i8(out, &sym_cnt, SYNC_BER);
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conv_encode_bert_frame(enc_bits, data); //BERT frames require 197 BERT bits packed as 25 bytes
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}
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//common stuff
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reorder_bits(rf_bits, enc_bits);
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randomize_bits(rf_bits);
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gen_data_i8(out, &sym_cnt, rf_bits);
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}
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/**
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* @brief Decode the Link Setup Frame from a symbol stream.
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*
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* @param lsf Pointer to an LSF struct.
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* @param pld_symbs Input 184 symbols represented as floats: {-3, -1, +1, +3}.
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* @return uint32_t Viterbi metric for the payload.
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*/
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uint32_t decode_LSF(lsf_t* lsf, const float pld_symbs[SYM_PER_PLD])
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{
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uint8_t lsf_b[30+1];
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uint16_t soft_bit[2*SYM_PER_PLD];
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uint16_t d_soft_bit[2*SYM_PER_PLD];
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uint32_t e;
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slice_symbols(soft_bit, pld_symbs);
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randomize_soft_bits(soft_bit);
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reorder_soft_bits(d_soft_bit, soft_bit);
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e = viterbi_decode_punctured(lsf_b, d_soft_bit, puncture_pattern_1, 2*SYM_PER_PLD, sizeof(puncture_pattern_1));
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//copy over the data starting at byte 1 (byte 0 needs to be omitted)
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memcpy(lsf->dst, &lsf_b[1+0], 6); //DST field
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memcpy(lsf->src, &lsf_b[1+6], 6); //SRC field
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lsf->type[0]=lsf_b[1+12]; //TYPE field
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lsf->type[1]=lsf_b[1+13];
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memcpy(lsf->meta, &lsf_b[1+14], 14); //META field
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lsf->crc[0]=lsf_b[1+28]; //CRC field
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lsf->crc[1]=lsf_b[1+29];
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return e; //return Viterbi error metric
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}
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/**
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* @brief Decode a single Stream Frame from a symbol stream.
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*
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* @param frame_data Pointer to a 16-byte array for the decoded payload.
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* @param lich Pointer to a 5-byte array for the decoded LICH data chunk.
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* @param fn Pointer to a uint16_t variable for the Frame Number.
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* @param lich_cnt Pointer to a uint8_t variable for the LICH Counter.
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* @param pld_symbs Input 184 symbols represented as floats: {-3, -1, +1, +3}.
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* @return uint32_t Viterbi metric for the payload.
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*/
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uint32_t decode_str_frame(uint8_t frame_data[16], uint8_t lich[5], uint16_t* fn, uint8_t* lich_cnt, const float pld_symbs[SYM_PER_PLD])
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{
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uint16_t soft_bit[2*SYM_PER_PLD];
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uint16_t d_soft_bit[2*SYM_PER_PLD];
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uint8_t tmp_frame_data[(16+128)/8+1]; //1 byte extra for flushing
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uint32_t e;
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slice_symbols(soft_bit, pld_symbs);
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randomize_soft_bits(soft_bit);
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reorder_soft_bits(d_soft_bit, soft_bit);
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//decode LICH
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uint8_t tmp[6];
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decode_LICH(tmp, d_soft_bit);
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memcpy(lich, tmp, 5);
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if(lich_cnt!=NULL) *lich_cnt = tmp[5]>>5;
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e = viterbi_decode_punctured(tmp_frame_data, &d_soft_bit[96], puncture_pattern_2, 2*SYM_PER_PLD-96, sizeof(puncture_pattern_2));
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//shift 1+2 positions left - get rid of the encoded flushing bits and FN
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memcpy(frame_data, &tmp_frame_data[1+2], 16);
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if(fn!=NULL) *fn = (tmp_frame_data[1]<<8)|tmp_frame_data[2];
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return e;
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}
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/**
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* @brief Decode a single Packet Frame from a symbol stream.
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*
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* @param frame_data Pointer to a 25-byte array for the decoded payload.
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* @param eof Pointer to a uint8_t variable for the End of Frame marker.
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* @param fn Pointer to a uint8_t variable for the Frame Number.
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* @param pld_symbs Input 184 symbols represented as floats: {-3, -1, +1, +3}.
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* @return uint32_t Viterbi metric for the payload.
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*/
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uint32_t decode_pkt_frame(uint8_t frame_data[25], uint8_t* eof, uint8_t* fn, const float pld_symbs[SYM_PER_PLD])
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{
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uint16_t soft_bit[2*SYM_PER_PLD];
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uint16_t d_soft_bit[2*SYM_PER_PLD];
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uint8_t tmp_frame_data[26+1]; //1 byte extra for flushing
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uint32_t e;
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slice_symbols(soft_bit, pld_symbs);
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randomize_soft_bits(soft_bit);
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reorder_soft_bits(d_soft_bit, soft_bit);
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e = viterbi_decode_punctured(tmp_frame_data, d_soft_bit, puncture_pattern_3, 2*SYM_PER_PLD, sizeof(puncture_pattern_3));
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//shift 1 position left - get rid of the encoded flushing bits
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memcpy(frame_data, &tmp_frame_data[1], 25);
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if(fn!=NULL) *fn = (tmp_frame_data[26]>>2)&0x1F;
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if(eof!=NULL) *eof = tmp_frame_data[26]>>7;
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return e;
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}
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