kopia lustrzana https://github.com/M17-Project/M17_Implementations
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Wojciech Kaczmarski
GitHub
rodzic
5eca167967
commit
ae53fe6636
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@ -0,0 +1,228 @@
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#include <string.h>
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#include <stdint.h>
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#include "golay.h"
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const uint16_t encode_matrix[12]=
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{
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0x8eb, 0x93e, 0xa97, 0xdc6, 0x367, 0x6cd,
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0xd99, 0x3da, 0x7b4, 0xf68, 0x63b, 0xc75
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};
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const uint16_t decode_matrix[12]=
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{
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0xc75, 0x49f, 0x93e, 0x6e3, 0xdc6, 0xf13,
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0xab9, 0x1ed, 0x3da, 0x7b4, 0xf68, 0xa4f
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};
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//0 index - LSB
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void IntToSoft(uint16_t* out, const uint16_t in, uint8_t len)
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{
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for(uint8_t i=0; i<len; i++)
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{
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(in>>i)&1 ? (out[i]=0xFFFF) : (out[i]=0);
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}
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}
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uint16_t SoftToInt(const uint16_t* in, uint8_t len)
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{
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uint16_t tmp=0;
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for(uint8_t i=0; i<len; i++)
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{
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if(in[i]>0x7FFF)
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tmp|=(1<<i);
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}
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return tmp;
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}
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//Quadrant I fixed point division with saturation
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//result=a/b
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uint16_t Div16(uint16_t a, uint16_t b)
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{
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uint32_t aa=a<<16;
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uint32_t r=aa/b;
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if(r<=0xFFFF)
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return r;
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else
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return 0xFFFF;
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}
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//Quadrant I fixed point multiplication
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//result=a/b
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uint16_t Mul16(uint16_t a, uint16_t b)
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{
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return (uint16_t)(((uint32_t)a*b)>>16);
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}
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//use bilinear interpolation for XOR
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uint16_t SoftBitXOR(const uint16_t a, const uint16_t b)
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{
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return Mul16(Div16(0xFFFF-b, 0xFFFF), Div16(a, 0xFFFF)) + Mul16(Div16(b, 0xFFFF), Div16(0xFFFF-a, 0xFFFF));
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}
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//soft XOR
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void SoftXOR(uint16_t* out, const uint16_t* a, const uint16_t* b, uint8_t len)
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{
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for(uint8_t i=0; i<len; i++)
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out[i]=SoftBitXOR(a[i], b[i]);
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}
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//soft equivalent of popcount
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uint32_t spopcount(const uint16_t* in, uint8_t siz)
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{
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uint32_t tmp=0;
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for(uint8_t i=0; i<siz; i++)
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tmp+=in[i];
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return tmp;
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}
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void calcChecksumS(uint16_t* out, const uint16_t* value)
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{
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uint16_t checksum[12];
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uint16_t soft_em[12]; //soft valued encoded matrix entry
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for(uint8_t i=0; i<12; i++)
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checksum[i]=0;
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for(uint8_t i=0; i<12; i++)
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{
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IntToSoft(soft_em, encode_matrix[i], 12);
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if(value[i]>0x7FFF)
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{
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SoftXOR(checksum, checksum, soft_em, 12);
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}
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}
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memcpy((uint8_t*)out, (uint8_t*)checksum, 12*2);
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}
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uint32_t SdetectErrors(const uint16_t* codeword)
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{
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uint16_t data[12];
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uint16_t parity[12];
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uint16_t cksum[12];
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uint16_t syndrome[12];
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uint32_t weight; //for soft popcount
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memcpy((uint8_t*)data, (uint8_t*)&codeword[12], 2*12);
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memcpy((uint8_t*)parity, (uint8_t*)&codeword[0], 2*12);
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calcChecksumS(cksum, data);
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SoftXOR(syndrome, parity, cksum, 12);
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weight=spopcount(syndrome, 12);
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//all (less than 4) errors in the parity part
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if(weight < 4*0xFFFE)
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{
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//printf("1: %1.2f\n", (float)weight/0xFFFF);
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return SoftToInt(syndrome, 12);
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}
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//one of the errors in data part, up to 3 in parity
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for(uint8_t i = 0; i<12; i++)
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{
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uint16_t e = 1<<i;
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uint16_t coded_error = encode_matrix[i];
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uint16_t scoded_error[12]; //soft coded_error
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uint16_t sc[12]; //syndrome^coded_error
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IntToSoft(scoded_error, coded_error, 12);
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SoftXOR(sc, syndrome, scoded_error, 12);
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weight=spopcount(sc, 12);
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if(weight < 3*0xFFFE)
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{
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//printf("2: %1.2f\n", (float)weight/0xFFFF+1);
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uint16_t s=SoftToInt(syndrome, 12);
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return (e << 12) | (s ^ coded_error);
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}
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}
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//two of the errors in data part and up to 2 in parity
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for(uint8_t i = 0; i<11; i++)
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{
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for(uint8_t j = i+1; j<12; j++)
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{
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uint16_t e = (1<<i) | (1<<j);
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uint16_t coded_error = encode_matrix[i]^encode_matrix[j];
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uint16_t scoded_error[12]; //soft coded_error
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uint16_t sc[12]; //syndrome^coded_error
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IntToSoft(scoded_error, coded_error, 12);
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SoftXOR(sc, syndrome, scoded_error, 12);
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weight=spopcount(sc, 12);
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if(weight < 2*0xFFFF)
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{
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//printf("3: %1.2f\n", (float)weight/0xFFFF+2);
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uint16_t s=SoftToInt(syndrome, 12);
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return (e << 12) | (s ^ coded_error);
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}
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}
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}
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//algebraic decoding magic
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uint16_t inv_syndrome[12]={0,0,0,0,0,0,0,0,0,0,0,0};
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uint16_t dm[12]; //soft decode matrix
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for(uint8_t i=0; i<12; i++)
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{
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if(syndrome[i] > 0x7FFF)
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{
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IntToSoft(dm, decode_matrix[i], 12);
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SoftXOR(inv_syndrome, inv_syndrome, dm, 12);
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}
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}
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//all (less than 4) errors in the data part
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weight=spopcount(inv_syndrome, 12);
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if(weight < 4*0xFFFF)
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{
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//printf("4: %1.2f\n", (float)weight/0xFFFF);
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return SoftToInt(inv_syndrome, 12) << 12;
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}
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//one error in parity bits, up to 3 in data - this part has some quirks, the reason remains unknown
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for(uint8_t i=0; i<12; i++)
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{
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uint16_t e = 1<<i;
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uint16_t coding_error = decode_matrix[i];
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uint16_t ce[12]; //soft coding error
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uint16_t tmp[12];
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IntToSoft(ce, coding_error, 12);
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SoftXOR(tmp, inv_syndrome, ce, 12);
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weight=spopcount(tmp, 12);
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if(weight < 3*(0xFFFF+2))
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{
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//printf("5: %1.2f\n", (float)weight/0xFFFF+1);
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return ((SoftToInt(inv_syndrome, 12) ^ coding_error) << 12) | e;
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}
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}
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return 0xFFFFFFFF;
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}
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//soft decode
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uint16_t golay24_sdecode(const uint16_t* codeword)
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{
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//match the bit order in M17
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uint16_t cw[24];
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for(uint8_t i=0; i<24; i++)
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cw[i]=codeword[23-i];
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uint32_t errors = SdetectErrors(cw);
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if(errors == 0xFFFFFFFF)
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return 0xFFFF;
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return (((SoftToInt(&cw[0], 16) | (SoftToInt(&cw[16], 8) << 16)) ^ errors) >> 12) & 0x0FFF;
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}
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@ -0,0 +1,15 @@
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#ifndef GOLAY_H
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#define GOLAY_H
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void IntToSoft(uint16_t* out, const uint16_t in, uint8_t len);
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uint16_t SoftToInt(const uint16_t* in, uint8_t len);
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uint16_t Div16(uint16_t a, uint16_t b);
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uint16_t Mul16(uint16_t a, uint16_t b);
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uint16_t SoftBitXOR(const uint16_t a, const uint16_t b);
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void SoftXOR(uint16_t* out, const uint16_t* a, const uint16_t* b, uint8_t len);
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uint32_t spopcount(const uint16_t* in, uint8_t siz);
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void calcChecksumS(uint16_t* out, const uint16_t* value);
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uint32_t SdetectErrors(const uint16_t* codeword);
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uint16_t golay24_sdecode(const uint16_t* codeword);
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#endif
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@ -2,9 +2,10 @@
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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 <sys/time.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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float sample;
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float last[8];
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@ -12,11 +13,39 @@ float xcorr;
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float pld[SYM_PER_PLD];
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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]; //deinterleaved soft bits
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uint16_t lich_chunk[96];
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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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uint8_t syncd=0;
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uint8_t pushed; //pushed symbols
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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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@ -41,7 +70,9 @@ int main(void)
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xcorr+=last[i]*str_sync[i];
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}
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if(xcorr>8.0)
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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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@ -112,8 +143,15 @@ int main(void)
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lich_chunk[i]=d_soft_bit[i];
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}
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//Golay decoder goes here
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decode_LICH(lich_b, lich_chunk);
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for(uint8_t i=0; i<6; i++)
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printf("%02X ", lich_b[i]);
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printf("\n");
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//debug - dump LICH
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uint8_t tmp;
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/*uint8_t tmp;
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for(uint16_t i=0; i<96; i++)
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{
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if(!(i%8))
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@ -123,9 +161,9 @@ int main(void)
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if(!((i+1)%8))
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write(STDOUT_FILENO, &tmp, 1);
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}
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tmp=0;
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tmp=0; //padding
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for(uint8_t i=0; i<4; i++)
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write(STDOUT_FILENO, &tmp, 1);
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write(STDOUT_FILENO, &tmp, 1);*/
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//job done
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syncd=0;
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