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Code cleanup and optimisation$

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AlexandreRouma
2022-07-08 17:30:43 +02:00
parent 3ab8badb6a
commit 30b6c2b1da
2 changed files with 15 additions and 96 deletions
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75
decoder_modules/radio/src/rds.cpp
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@ -20,53 +20,21 @@ namespace rds {
{ BLOCK_TYPE_D, 0b0110110100 }
};
// This parity check matrix is given in annex B2.1 of the specificiation
const uint16_t PARITY_CHECK_MAT[] = {
0b1000000000,
0b0100000000,
0b0010000000,
0b0001000000,
0b0000100000,
0b0000010000,
0b0000001000,
0b0000000100,
0b0000000010,
0b0000000001,
0b1011011100,
0b0101101110,
0b0010110111,
0b1010000111,
0b1110011111,
0b1100010011,
0b1101010101,
0b1101110110,
0b0110111011,
0b1000000001,
0b1111011100,
0b0111101110,
0b0011110111,
0b1010100111,
0b1110001111,
0b1100011011
};
// 9876543210
const uint16_t LFSR_POLY = 0b0110111001;
const uint16_t IN_POLY = 0b1100011011;
const int BLOCK_LEN = 26;
const int DATA_LEN = 16;
const int POLY_LEN = 10;
// 9876543210
const uint16_t LFSR_POLY = 0b0110111001;
const uint16_t IN_POLY = 0b1100011011;
void RDSDecoder::process(uint8_t* symbols, int count) {
for (int i = 0; i < count; i++) {
// Shift in the bit
shiftReg = ((shiftReg << 1) & 0x3FFFFFF) | (symbols[i] & 1);
// Skip if we need to shift in new data
if (--skip > 0) {
continue;
}
if (--skip > 0) { continue; }
// Calculate the syndrome and update sync status
uint16_t syn = calcSyndrome(shiftReg);
@ -109,23 +77,9 @@ namespace rds {
}
uint16_t RDSDecoder::calcSyndrome(uint32_t block) {
// Perform vector/matrix dot product between block and parity matrix
uint16_t syn = 0;
for(int i = 0; i < BLOCK_LEN; i++) {
syn ^= PARITY_CHECK_MAT[BLOCK_LEN - 1 - i] * ((block >> i) & 1);
}
return syn;
}
uint32_t RDSDecoder::correctErrors(uint32_t block, BlockType type, bool& recovered) {
// Subtract the offset from block
block ^= (uint32_t)OFFSETS[type];
// Init the syndrome and output
uint16_t syn = 0;
uint32_t out = block;
// Feed in the data
// Calculate the syndrome using a LFSR
for (int i = BLOCK_LEN - 1; i >= 0; i--) {
// Shift the syndrome and keep the output
uint8_t outBit = (syn >> (POLY_LEN - 1)) & 1;
@ -138,7 +92,16 @@ namespace rds {
syn ^= IN_POLY * ((block >> i) & 1);
}
uint16_t firstSyn = syn;
return syn;
}
uint32_t RDSDecoder::correctErrors(uint32_t block, BlockType type, bool& recovered) {
// Subtract the offset from block
block ^= (uint32_t)OFFSETS[type];
uint32_t out = block;
// Calculate syndrome of corrected block
uint16_t syn = calcSyndrome(block);
// Use the syndrome register to do error correction if errors are present
uint8_t errorFound = 0;
@ -158,14 +121,6 @@ namespace rds {
}
recovered = !(syn & 0b11111);
// // One last check
// if (errorFound) {
// printf("Error found: %04X -> %04X, %08X -> %08X\n", firstSyn, syn, block, out);
// }
// else if (!recovered) {
// printf("Non recoverable error\n");
// }
return out;
}