kopia lustrzana https://github.com/M17-Project/M17_Implementations
Delete m17-decoder-sym.c
Wojciech Kaczmarski
GitHub
rodzic
a94cdc229c
commit
3cd2b62ad5
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <stdint.h>
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#include <string.h>
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#include "m17.h"
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#include "golay.h"
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#include "viterbi.h"
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float sample; //last raw sample from the stdin
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float last[8]; //look-back buffer for finding syncwords
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float xcorr; //cross correlation for finding syncwords
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float pld[SYM_PER_PLD]; //raw frame symbols
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uint16_t soft_bit[2*SYM_PER_PLD]; //raw frame soft bits
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uint16_t d_soft_bit[2*SYM_PER_PLD]; //deinterleaved soft bits
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uint8_t lsf[30]; //complete LSF
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uint16_t lich_chunk[96]; //raw, soft LSF chunk extracted from the LICH
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uint8_t lich_b[6]; //48-bit decoded LICH
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uint8_t lich_cnt; //LICH_CNT
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uint8_t lich_chunks_rcvd=0; //flags set for each LSF chunk received
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uint16_t enc_data[272]; //raw frame data soft bits
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uint8_t frame_data[19]; //decoded frame data, 144 bits (16+128), plus 4 flushing bits
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uint8_t syncd=0; //syncword found?
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uint8_t pushed; //counter for pushed symbols
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extern const uint8_t P2_pat[12];
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//soft decodes LICH into a 6-byte array
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//input - soft bits
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//output - an array of packed bits
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void decode_LICH(uint8_t* outp, const uint16_t* inp)
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{
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uint16_t tmp;
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memset(outp, 0, 5);
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tmp=golay24_sdecode(&inp[0]);
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outp[0]=(tmp>>4)&0xFF;
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outp[1]|=(tmp&0xF)<<4;
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tmp=golay24_sdecode(&inp[1*24]);
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outp[1]|=(tmp>>8)&0xF;
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outp[2]=tmp&0xFF;
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tmp=golay24_sdecode(&inp[2*24]);
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outp[3]=(tmp>>4)&0xFF;
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outp[4]|=(tmp&0xF)<<4;
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tmp=golay24_sdecode(&inp[3*24]);
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outp[4]|=(tmp>>8)&0xF;
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outp[5]=tmp&0xFF;
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}
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int main(void)
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{
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while(1)
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{
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//wait for another symbol
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while(read(STDIN_FILENO, (uint8_t*)&sample, 4)<4);
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if(!syncd)
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{
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//push new symbol
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for(uint8_t i=0; i<7; i++)
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{
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last[i]=last[i+1];
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}
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last[7]=sample;
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//calculate cross-correlation
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xcorr=0;
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for(uint8_t i=0; i<8; i++)
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{
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xcorr+=last[i]*str_sync[i];
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}
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//printf("%f\n", xcorr);
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if(xcorr>62.0)
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{
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syncd=1;
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pushed=0;
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}
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else if(xcorr<-62)
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{
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printf("LSF\n");
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}
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}
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else
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{
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pld[pushed++]=sample;
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if(pushed==SYM_PER_PLD)
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{
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//decode symbols to soft dibits
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for(uint8_t i=0; i<SYM_PER_PLD; i++)
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{
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//bit 0
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if(pld[i]>=symbs[3])
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{
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soft_bit[i*2+1]=0xFFFF;
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}
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else if(pld[i]>=symbs[2])
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{
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soft_bit[i*2+1]=-(float)0xFFFF/(symbs[3]-symbs[2])*symbs[2]+pld[i]*(float)0xFFFF/(symbs[3]-symbs[2]);
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}
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else if(pld[i]>=symbs[1])
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{
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soft_bit[i*2+1]=0x0000;
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}
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else if(pld[i]>=symbs[0])
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{
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soft_bit[i*2+1]=(float)0xFFFF/(symbs[1]-symbs[0])*symbs[1]-pld[i]*(float)0xFFFF/(symbs[1]-symbs[0]);
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}
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else
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{
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soft_bit[i*2+1]=0xFFFF;
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}
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//bit 1
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if(pld[i]>=symbs[2])
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{
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soft_bit[i*2]=0x0000;
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}
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else if(pld[i]>=symbs[1])
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{
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soft_bit[i*2]=0x7FFF-pld[i]*(float)0xFFFF/(symbs[2]-symbs[1]);
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}
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else
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{
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soft_bit[i*2]=0xFFFF;
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}
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}
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//derandomize
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for(uint16_t i=0; i<SYM_PER_PLD*2; i++)
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{
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if((rand_seq[i/8]>>(7-(i%8)))&1) //soft XOR. flip soft bit if "1"
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soft_bit[i]=0xFFFF-soft_bit[i];
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}
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//deinterleave
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for(uint16_t i=0; i<SYM_PER_PLD*2; i++)
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{
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d_soft_bit[i]=soft_bit[intrl_seq[i]];
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}
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//extract LICH
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for(uint16_t i=0; i<96; i++)
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{
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lich_chunk[i]=d_soft_bit[i];
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}
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//Golay decoder
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decode_LICH(lich_b, lich_chunk);
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lich_cnt=lich_b[5]>>5;
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lich_chunks_rcvd|=(1<<lich_cnt);
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memcpy(&lsf[lich_cnt*5], lich_b, 5);
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//debug - dump LICH
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if(lich_chunks_rcvd==0x3F)
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{
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//DST
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printf("DST: ");
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for(uint8_t i=0; i<6; i++)
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printf("%02X", lsf[i]);
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printf(" ");
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//SRC
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printf("SRC: ");
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for(uint8_t i=0; i<6; i++)
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printf("%02X", lsf[6+i]);
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printf(" ");
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//TYPE
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printf("TYPE: ");
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for(uint8_t i=0; i<2; i++)
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printf("%02X", lsf[12+i]);
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printf(" ");
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//META
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printf("META: ");
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for(uint8_t i=0; i<14; i++)
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printf("%02X", lsf[14+i]);
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printf(" ");
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//CRC
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printf("CRC: ");
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for(uint8_t i=0; i<2; i++)
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printf("%02X", lsf[28+i]);
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printf("\n");
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lich_chunks_rcvd=0; //reset all flags
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}
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//extract data
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for(uint16_t i=0; i<272; i++)
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{
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enc_data[i]=d_soft_bit[96+i];
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}
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//data part
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uint32_t e=decodePunctured(frame_data, enc_data, P2_pat, 272, 12);
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//dump data - first byte is empty
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printf("FN: %02X%02X PLD: ", frame_data[1], frame_data[2]);
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for(uint8_t i=3; i<19; i++)
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{
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printf("%02X", frame_data[i]);
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}
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printf(" e=%1.1f\n", (float)e/0xFFFF);
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//job done
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syncd=0;
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pushed=0;
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for(uint8_t i=0; i<8; i++)
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last[i]=0.0;
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}
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}
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}
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return 0;
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}
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