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Tighter sync detection for YSF.

This commit is contained in:
Jonathan Naylor 2016-06-06 18:07:33 +01:00
parent b8457aed4c
commit 6c66f56e54
1 changed files with 7 additions and 5 deletions
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12
YSFRX.cpp
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@ -31,8 +31,10 @@ const uint32_t PLLMAX = 0x10000U;
const uint32_t PLLINC = PLLMAX / YSF_RADIO_SYMBOL_LENGTH; const uint32_t PLLINC = PLLMAX / YSF_RADIO_SYMBOL_LENGTH;
const uint32_t INC = PLLINC / 32U; const uint32_t INC = PLLINC / 32U;
const uint8_t SYNC_SYMBOL_ERRS = 2U; const uint8_t SYNC_SYMBOL_ERRS = 0U;
const uint8_t SYNC_BIT_ERRS = 4U;
const uint8_t SYNC_BIT_START_ERRS = 2U;
const uint8_t SYNC_BIT_RUN_ERRS = 4U;
const unsigned int MAX_SYNC_FRAMES = 4U + 1U; const unsigned int MAX_SYNC_FRAMES = 4U + 1U;
@ -158,7 +160,7 @@ void CYSFRX::processNone(q15_t sample)
} }
// Fuzzy matching of the data sync bit sequence // Fuzzy matching of the data sync bit sequence
if (countBits64((m_bitBuffer & YSF_SYNC_BITS_MASK) ^ YSF_SYNC_BITS) <= SYNC_BIT_ERRS) { if (countBits64((m_bitBuffer & YSF_SYNC_BITS_MASK) ^ YSF_SYNC_BITS) <= SYNC_BIT_START_ERRS) {
DEBUG5("YSFRX: sync found in None min/max/centre/threshold", min, max, centre, threshold); DEBUG5("YSFRX: sync found in None min/max/centre/threshold", min, max, centre, threshold);
for (uint8_t i = 0U; i < YSF_SYNC_LENGTH_BYTES; i++) for (uint8_t i = 0U; i < YSF_SYNC_LENGTH_BYTES; i++)
m_buffer[i] = YSF_SYNC_BYTES[i]; m_buffer[i] = YSF_SYNC_BYTES[i];
@ -212,10 +214,10 @@ void CYSFRX::processData(q15_t sample)
m_bufferPtr++; m_bufferPtr++;
} }
// Only search for a sync in the right place +-1 symbol // Only search for a sync in the right place +-2 symbols
if (m_bufferPtr >= (YSF_SYNC_LENGTH_BITS - 2U) && m_bufferPtr <= (YSF_SYNC_LENGTH_BITS + 2U)) { if (m_bufferPtr >= (YSF_SYNC_LENGTH_BITS - 2U) && m_bufferPtr <= (YSF_SYNC_LENGTH_BITS + 2U)) {
// Fuzzy matching of the data sync bit sequence // Fuzzy matching of the data sync bit sequence
if (countBits64((m_bitBuffer & YSF_SYNC_BITS_MASK) ^ YSF_SYNC_BITS) <= SYNC_BIT_ERRS) { if (countBits64((m_bitBuffer & YSF_SYNC_BITS_MASK) ^ YSF_SYNC_BITS) <= SYNC_BIT_RUN_ERRS) {
DEBUG2("YSFRX: found sync in Data, pos", m_bufferPtr - YSF_SYNC_LENGTH_BITS); DEBUG2("YSFRX: found sync in Data, pos", m_bufferPtr - YSF_SYNC_LENGTH_BITS);
m_lostCount = MAX_SYNC_FRAMES; m_lostCount = MAX_SYNC_FRAMES;
m_bufferPtr = YSF_SYNC_LENGTH_BITS; m_bufferPtr = YSF_SYNC_LENGTH_BITS;