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35 lines
803 B
C
35 lines
803 B
C
/*
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Interleaving is "easiest" if the same number of bits is used per symbol as for FEC
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Chosen mode "spreading 8, low rate" has 6 bits per symbol, so use 4:6 FEC
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*/
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// Needs adjusting for different sizes
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void LoRaDemod::interleave(short* inout)
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{
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int i, index = 6;
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short in[index * 2];
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for (i = 0; i < index; i++)
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in[i] = inout[i];
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for (i = 0; i < index; i++) {
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inout[i] = (1 & in[0 + i]) | (2 & in[1 + i]) | (4 & in[2 + i])
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| (8 & in[3 + i]) | (16 & in[4 + i]) | (32 & in[5 + i]);
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in[i + index] = in[i];
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}
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}
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// Same sequence for any size
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void LoRaDemod::make_gray()
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{
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short k = 0;
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for (short i = 0; i < 1<<8; i++) {
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gray[i] = k;
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// ungray[k] = i;
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short r = (i+1) & ~i;
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k ^= r;
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}
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// for (short i = 0; i < 1<<5; i++)
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// printf("%x:%x:%x.\n", i, gray[i], ungray[gray[i]]);
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}
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