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Wojciech Kaczmarski
GitHub
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28d7120712
commit
5c67546878
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#include <stdio.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#define LEAD_PREAM 40 //first (lead) preamble length in ms
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static const uint16_t golay_encode_matrix[12]=
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{
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0xC75,
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0x49F,
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0xD4B,
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0x6E3,
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0x9B3,
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0xB66,
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0xECC,
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0x1ED,
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0x3DA,
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0x7B4,
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0xB1D,
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0xE3A,
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};
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//An union for easy access to DEST_ and SRC_ADDR byte values
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union addr
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{
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uint64_t val;
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uint8_t byte[8];
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} dest_addr, src_addr;
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const uint8_t pream[8]={0,1,1,1,0,1,1,1}; //preamble
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const uint8_t sync_1[2]={0x32, 0x43}; //SYNC for the link setup frame
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const uint8_t sync_2[2]={0x2B, 0x7E}; //SYNC for all subsequent frames
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uint8_t ConvolLUT[32]; //a look-up table for convolutional encoder
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uint8_t type_1[30]; //type-1 packed bits
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uint8_t type_1_u[300]; //type-1 unpacked bits
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uint8_t type_2[500]; //type-2 unpacked bits
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uint8_t type_3[384];
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uint8_t type_4[384];
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FILE *f_out;
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//Takes an ASCII callsign in a null terminated char* and encodes it using base 40.
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//Returns -1 (all Fs) if the provided callsign is longer than 9 characters, which
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//would over-flow the 48 bits we have for the callsign. log2(40^9) = 47.9
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uint64_t encode_callsign_base40(const char *callsign)
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{
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if (strlen(callsign) > 9)
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return -1;
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uint64_t encoded = 0;
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for (const char *p = (callsign + strlen(callsign) - 1); p >= callsign; p--)
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{
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encoded *= 40;
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// If speed is more important than code space, you can replace this with a lookup into a 256 byte array.
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if (*p >= 'A' && *p <= 'Z') // 1-26
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encoded += *p - 'A' + 1;
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else if (*p >= '0' && *p <= '9') // 27-36
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encoded += *p - '0' + 27;
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else if (*p == '-') // 37
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encoded += 37;
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// These are just place holders. If other characters make more sense, change these.
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// Be sure to change them in the decode array below too.
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else if (*p == '/') // 38
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encoded += 38;
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else if (*p == '.') // 39
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encoded += 39;
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else
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// Invalid character, represented by 0.
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// Interesting artifact of using zero to flag an invalid character: invalid characters
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// at the end of the callsign won't show up as flagged at the recipient. Because zero
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// also flags the end of the callsign. (This started as a bug, losing As at the end of
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// the callsign, which is why A is no longer the beginning of the mapping array.)
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//printf("Invalid character: %c\n", *p);
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//encoded += 0;
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;
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}
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return encoded;
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}
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//Returns the golay coding of the given 12-bit word
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static uint16_t golay_coding(uint16_t w)
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{
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uint16_t out=0;
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for(uint16_t i=0; i<12; i++)
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{
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if( w & 1<<i )
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out ^= golay_encode_matrix[i];
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}
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return out;
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}
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uint32_t golay_encode(uint16_t w)
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{
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return ((uint32_t)w)|((uint32_t)golay_coding(w))<<12;
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}
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//Initializes a Look Up Table for constraint K=5 and polynomials below
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//G_1=1+D^3+D^4
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//G_2=1+D+D^2+D^4
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void ConvolInitLUT(uint8_t *dest)
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{
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uint8_t g1, g2;
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memset(dest, 0, 32);
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//for all 2^5 states
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for(uint8_t i=0; i<32; i++)
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{
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g1=( ((i>>4)&1) + ((i>>1)&1) + ((i>>0)&1) )&1; //G_1=1+D^3+D^4
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g2=( ((i>>4)&1) + ((i>>3)&1) + ((i>>2)&1) + ((i>>0)&1))&1; //G_2=1+D+D^2+D^4
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dest[i]=(g1<<1)|g2;
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}
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}
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//Takes *len* bytes of packed data and convolutionally encodes them
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//Constraint length K=5
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//rate r=1/2
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//G_1=1+D^3+D^4
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//G_2=1+D+D^2+D^4
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void ConvolEncode(uint8_t *lut, uint8_t *data_in, uint8_t *data_out, uint16_t len)
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{
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uint8_t sr=0;
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//len*8 bits of data + 4 tail bits
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for(uint16_t num_pushed=0; num_pushed<(len*8+4); num_pushed++)
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{
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sr>>=1;
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sr|=((data_in[num_pushed/8]>>(num_pushed%8))&1)<<4;
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//we are using a LUT for this
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if(data_out!=NULL)
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data_out[num_pushed/4]|=lut[sr]<<(6-((num_pushed*2)%8)); //changed order of dibits!
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printf("%d%d", lut[sr]>>1, lut[sr]&1);
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}
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}
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//Punctures the mother code of rate 1/2
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//pattern I: leaving 46 from 61 bits
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//for the link setup frame
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void ConvolPuncture46_61(uint8_t *in, uint8_t *out)
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{
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uint8_t punct_pattern[61]={1, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1,
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0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 1};
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;//
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}
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/*
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Params:
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./this out_file dest_addr src_addr
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*/
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int main(int argc, char *argv[])
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{
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uint16_t type=(1<<0)|(0b10<<2); //FIXME: type indicator - stream, voice, codec2 3200bps, no encryption
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uint8_t nonce[16]={0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0};
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if(argc==4)
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{
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dest_addr.val=encode_callsign_base40(argv[2]);
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src_addr.val=encode_callsign_base40(argv[3]);
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printf("DEST\t0x%012llX\n", dest_addr.val);
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printf("SRC \t0x%012llX\n", src_addr.val);
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f_out=fopen(argv[1], "wb");
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//preamble
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for(uint16_t i=0; i<(LEAD_PREAM*9600)/1000; i++)
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fwrite(&pream[i%8], 1, 1, f_out);
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//2-byte sync
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for(uint8_t i=0; i<16; i++)
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{
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uint8_t one=1, zero=0;
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if((sync_1[i/8]>>(7-(i%8)))&1)
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fwrite(&one, 1, 1, f_out);
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else
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fwrite(&zero, 1, 1, f_out);
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}
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memcpy(&type_1[0], dest_addr.byte, 6); //DST 48 bits
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memcpy(&type_1[6], src_addr.byte, 6); //SRC 48 bits
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memcpy(&type_1[12], (uint8_t*)&type, 2); //TYPE 16 bits
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memcpy(&type_1[14], nonce, 16); //NONCE 128 bits
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//unpacking type-1 bits
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for(uint8_t i=0; i<30; i++)
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{
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for(uint8_t j=0; j<8; j++)
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{
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type_1_u[i*8+j]=type_1[i]>>(7-j);
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}
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}
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//convolutionally encode type-1 to type-2
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;
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fclose(f_out);
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return 0;
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}
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else
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{
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printf("Not enough params\n");
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return 1;
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}
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}
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@ -0,0 +1,55 @@
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/********************************************\
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Crap generator for the M17 4FSK modulator
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\********************************************/
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <time.h>
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#define SF_NUM 620 //how namy superframes of crap?
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FILE *fp;
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uint8_t preamble[48];
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uint8_t sync[2]={0x32, 0x43};
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uint8_t filler[46];
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int main(void)
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{
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time_t tt;
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srand(time(&tt));
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memset(preamble, 0xDD, 48);
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fp = fopen("dummy.bin", "wb");
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//preamble
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fwrite(preamble, 1, 48, fp);
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//fake LICH
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fwrite(sync, 1, 2, fp);
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for(uint8_t j=0; j<46; j++)
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filler[j]=rand()%0xFF;
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fwrite(filler, 1, 46, fp);
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//fake data
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for(uint16_t sf=0; sf<SF_NUM; sf++)
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{
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for(uint8_t i=0; i<5; i++)
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{
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fwrite(sync, 1, 2, fp);
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for(uint8_t j=0; j<46; j++)
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filler[j]=rand()%0xFF;
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fwrite(filler, 1, 46, fp);
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}
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}
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fclose(fp);
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return 0;
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}
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