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Add SINC filter for NXDN modulator and new deviation values

nxdn
Andy CA6JAU 2018-02-08 21:31:45 -03:00
parent 16d978cea2
commit 3ea95ce53d
2 changed files with 21 additions and 5 deletions
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24
NXDNTX.cpp
View File

@ -32,10 +32,14 @@ static q15_t RRC_0_2_FILTER[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 850, 592, 219, -234,
-1597, -1795, -1769, -1548, -1179, -720, -234, 219, 592, 850}; // numTaps = 90, L = 10
const uint16_t RRC_0_2_FILTER_PHASE_LEN = 9U; // phaseLength = numTaps/L
const q15_t NXDN_LEVELA = 840;
const q15_t NXDN_LEVELB = 280;
const q15_t NXDN_LEVELC = -280;
const q15_t NXDN_LEVELD = -840;
static q15_t NXDN_SINC_FILTER[] = {572, -1003, -253, 254, 740, 1290, 1902, 2527, 3090, 3517, 3747, 3747, 3517, 3090, 2527, 1902,
1290, 740, 254, -253, -1003, 572};
const uint16_t NXDN_SINC_FILTER_LEN = 22U;
const q15_t NXDN_LEVELA = 735;
const q15_t NXDN_LEVELB = 245;
const q15_t NXDN_LEVELC = -245;
const q15_t NXDN_LEVELD = -735;
const uint8_t NXDN_PREAMBLE[] = {0x57U, 0x75U, 0xFDU};
const uint8_t NXDN_SYNC = 0x5FU;
@ -43,18 +47,25 @@ const uint8_t NXDN_SYNC = 0x5FU;
CNXDNTX::CNXDNTX() :
m_buffer(1500U),
m_modFilter(),
m_sincFilter(),
m_modState(),
m_sincState(),
m_poBuffer(),
m_poLen(0U),
m_poPtr(0U),
m_txDelay(240U) // 200ms
{
::memset(m_modState, 0x00U, 16U * sizeof(q15_t));
::memset(m_sincState, 0x00U, 70U * sizeof(q15_t));
m_modFilter.L = NXDN_RADIO_SYMBOL_LENGTH;
m_modFilter.phaseLength = RRC_0_2_FILTER_PHASE_LEN;
m_modFilter.pCoeffs = RRC_0_2_FILTER;
m_modFilter.pState = m_modState;
m_sincFilter.numTaps = NXDN_SINC_FILTER_LEN;
m_sincFilter.pState = m_sincState;
m_sincFilter.pCoeffs = NXDN_SINC_FILTER;
}
void CNXDNTX::process()
@ -115,6 +126,7 @@ uint8_t CNXDNTX::writeData(const uint8_t* data, uint8_t length)
void CNXDNTX::writeByte(uint8_t c)
{
q15_t inBuffer[4U];
q15_t intBuffer[NXDN_RADIO_SYMBOL_LENGTH * 4U];
q15_t outBuffer[NXDN_RADIO_SYMBOL_LENGTH * 4U];
const uint8_t MASK = 0xC0U;
@ -136,7 +148,9 @@ void CNXDNTX::writeByte(uint8_t c)
}
}
::arm_fir_interpolate_q15(&m_modFilter, inBuffer, outBuffer, 4U);
::arm_fir_interpolate_q15(&m_modFilter, inBuffer, intBuffer, 4U);
::arm_fir_fast_q15(&m_sincFilter, intBuffer, outBuffer, NXDN_RADIO_SYMBOL_LENGTH * 4U);
io.write(STATE_NXDN, outBuffer, NXDN_RADIO_SYMBOL_LENGTH * 4U);
}

2
NXDNTX.h
View File

@ -38,7 +38,9 @@ public:
private:
CSerialRB m_buffer;
arm_fir_interpolate_instance_q15 m_modFilter;
arm_fir_instance_q15 m_sincFilter;
q15_t m_modState[16U]; // blockSize + phaseLength - 1, 4 + 9 - 1 plus some spare
q15_t m_sincState[70U]; // NoTaps + BlockSize - 1, 22 + 40 - 1 plus some spare
uint8_t m_poBuffer[1200U];
uint16_t m_poLen;
uint16_t m_poPtr;