mirror of https://github.com/g4klx/MMDVM.git
Add a smoothing filter to the POCSAG TX waveform.
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parent
88c530d9e6
commit
dcd8142c51
21
POCSAGTX.cpp
21
POCSAGTX.cpp
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@ -29,15 +29,25 @@ const uint16_t POCSAG_RADIO_SYMBOL_LENGTH = 20U;
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const q15_t POCSAG_LEVEL1[] = { 1700, 1700, 1700, 1700, 1700, 1700, 1700, 1700, 1700, 1700, 1700, 1700, 1700, 1700, 1700, 1700, 1700, 1700, 1700, 1700};
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const q15_t POCSAG_LEVEL0[] = {-1700, -1700, -1700, -1700, -1700, -1700, -1700, -1700, -1700, -1700, -1700, -1700, -1700, -1700, -1700, -1700, -1700, -1700, -1700, -1700};
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static q15_t SHAPING_FILTER[] = {5461, 5461, 5461, 5461, 5461, 5461};
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const uint16_t SHAPING_FILTER_LEN = 6U;
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const uint8_t POCSAG_SYNC = 0xAAU;
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CPOCSAGTX::CPOCSAGTX() :
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m_buffer(4000U),
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m_modFilter(),
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m_modState(),
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m_poBuffer(),
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m_poLen(0U),
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m_poPtr(0U),
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m_txDelay(POCSAG_PREAMBLE_LENGTH_BYTES)
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{
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::memset(m_modState, 0x00U, 170U * sizeof(q15_t));
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m_modFilter.numTaps = SHAPING_FILTER_LEN;
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m_modFilter.pState = m_modState;
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m_modFilter.pCoeffs = SHAPING_FILTER;
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}
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void CPOCSAGTX::process()
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@ -94,7 +104,8 @@ uint8_t CPOCSAGTX::writeData(const uint8_t* data, uint8_t length)
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void CPOCSAGTX::writeByte(uint8_t c)
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{
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q15_t buffer[POCSAG_RADIO_SYMBOL_LENGTH * 8U];
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q15_t inBuffer[POCSAG_RADIO_SYMBOL_LENGTH * 8U];
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q15_t outBuffer[POCSAG_RADIO_SYMBOL_LENGTH * 8U];
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const uint8_t MASK = 0x80U;
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@ -102,15 +113,17 @@ void CPOCSAGTX::writeByte(uint8_t c)
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for (uint8_t i = 0U; i < 8U; i++, c <<= 1, n += POCSAG_RADIO_SYMBOL_LENGTH) {
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switch (c & MASK) {
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case 0x80U:
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::memcpy(buffer + n, POCSAG_LEVEL1, POCSAG_RADIO_SYMBOL_LENGTH * sizeof(q15_t));
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::memcpy(inBuffer + n, POCSAG_LEVEL1, POCSAG_RADIO_SYMBOL_LENGTH * sizeof(q15_t));
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break;
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default:
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::memcpy(buffer + n, POCSAG_LEVEL0, POCSAG_RADIO_SYMBOL_LENGTH * sizeof(q15_t));
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::memcpy(inBuffer + n, POCSAG_LEVEL0, POCSAG_RADIO_SYMBOL_LENGTH * sizeof(q15_t));
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break;
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}
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}
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io.write(STATE_POCSAG, buffer, POCSAG_RADIO_SYMBOL_LENGTH * 8U);
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::arm_fir_fast_q15(&m_modFilter, inBuffer, outBuffer, POCSAG_RADIO_SYMBOL_LENGTH * 8U);
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io.write(STATE_POCSAG, outBuffer, POCSAG_RADIO_SYMBOL_LENGTH * 8U);
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}
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void CPOCSAGTX::setTXDelay(uint8_t delay)
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12
POCSAGTX.h
12
POCSAGTX.h
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@ -36,11 +36,13 @@ public:
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uint8_t getSpace() const;
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private:
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CSerialRB m_buffer;
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uint8_t m_poBuffer[1200U];
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uint16_t m_poLen;
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uint16_t m_poPtr;
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uint16_t m_txDelay;
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CSerialRB m_buffer;
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arm_fir_instance_q15 m_modFilter;
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q15_t m_modState[170U]; // NoTaps + BlockSize - 1, 6 + 160 - 1 plus some spare
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uint8_t m_poBuffer[1200U];
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uint16_t m_poLen;
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uint16_t m_poPtr;
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uint16_t m_txDelay;
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void writeByte(uint8_t c);
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};
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