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First woring AX.25 decoder (in simulation).

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This commit is contained in:
Jonathan Naylor
2020-06-17 15:28:41 +01:00
parent e332dbba8e
commit af11be16dc
4 changed files with 332 additions and 133 deletions
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AX25Demodulator.cpp
+23 -26
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@@ -21,27 +21,27 @@
#include "Globals.h"
#include "AX25Demodulator.h"
const float32_t DELAY = 0.000448F;
const float32_t SAMPLE_RATE = 24000.0F;
const float32_t SYMBOL_RATE = 1200.0F;
const uint16_t DELAY_LEN = uint16_t((DELAY / (1.0F / SAMPLE_RATE)) + 0.5F);
const uint16_t DELAY_LEN = 11U;
const float32_t SAMPLES_PER_SYMBOL = SAMPLE_RATE / SYMBOL_RATE;
const float32_t PLL_LIMIT = SAMPLES_PER_SYMBOL / 2.0F;
// XXX This is for the wrong sample rate
const uint32_t LPF_FILTER_LEN = 96U;
q15_t LPF_FILTER_COEFFS[] = {
0, 1, 3, 5, 8, 11, 14, 17, 19, 20, 18, 14,
7, -2, -16, -33, -53, -76, -101, -126, -151, -174, -194, -208,
-215, -212, -199, -173, -133, -79, -10, 74, 173, 287, 413, 549,
693, 842, 993, 1142, 1287, 1423, 1547, 1656, 1747, 1817, 1865, 1889,
1889, 1865, 1817, 1747, 1656, 1547, 1423, 1287, 1142, 993, 842, 693,
549, 413, 287, 173, 74, -10, -79, -133, -173, -199, -212, -215,
-208, -194, -174, -151, -126, -101, -76, -53, -33, -16, -2, 7,
14, 18, 20, 19, 17, 14, 11, 8, 5, 3, 1, 0,
0, 0, 0, 1, 2, 5, 8, 12, 18, 23,
29, 33, 36, 36, 33, 25, 13, -5, -28, -57,
-89, -123, -159, -194, -225, -249, -264, -267, -254, -224,
-175, -104, -12, 102, 236, 389, 557, 738, 926, 1117,
1306, 1486, 1654, 1802, 1927, 2025, 2092, 2126, 2126, 2092,
2025, 1927, 1802, 1654, 1486, 1306, 1117, 926, 738, 557,
389, 236, 102, -12, -104, -175, -224, -254, -267, -264,
-249, -225, -194, -159, -123, -89, -57, -28, -5, 13,
25, 33, 36, 36, 33, 29, 23, 18, 12, 8,
5, 2, 1, 0, 0, 0
};
// 64 Hz loop filter.
@@ -53,7 +53,7 @@ const uint32_t PLL_FILTER_LEN = 7U;
float32_t PLL_FILTER_COEFFS[] = {3.196252e-02F, 1.204223e-01F, 2.176819e-01F, 2.598666e-01F, 2.176819e-01F, 1.204223e-01F, 3.196252e-02F};
CAX25Demodulator::CAX25Demodulator(float32_t* coeffs, uint16_t length) :
CAX25Demodulator::CAX25Demodulator(q15_t* coeffs, uint16_t length) :
m_frame(),
m_audioFilter(),
m_audioState(),
@@ -73,7 +73,7 @@ m_hdlcBuffer(0U),
m_hdlcBits(0U),
m_hdlcState(AX25_IDLE)
{
m_delayLine = new bool[2U * DELAY_LEN];
m_delayLine = new bool[DELAY_LEN];
m_audioFilter.numTaps = length;
m_audioFilter.pState = m_audioState;
@@ -88,22 +88,17 @@ m_hdlcState(AX25_IDLE)
m_pllFilter.pCoeffs = PLL_FILTER_COEFFS;
}
bool CAX25Demodulator::process(const q15_t* samples, uint8_t length, CAX25Frame& frame)
bool CAX25Demodulator::process(q15_t* samples, uint8_t length, CAX25Frame& frame)
{
bool result = false;
float32_t input[RX_BLOCK_SIZE];
for (size_t i = 0; i < length; i++)
input[i] = float(samples[i]);
float32_t fa[RX_BLOCK_SIZE];
::arm_fir_f32(&m_audioFilter, input, fa, RX_BLOCK_SIZE);
q15_t fa[RX_BLOCK_SIZE];
::arm_fir_fast_q15(&m_audioFilter, samples, fa, RX_BLOCK_SIZE);
int16_t buffer[RX_BLOCK_SIZE];
for (uint8_t i = 0; i < length; i++) {
int16_t sample = int16_t(fa[i]);
bool level = (sample >= 0);
bool delayed = delay(level);
bool level = (fa[i] >= 0);
bool delayed = delay(level);
buffer[i] = (int16_t(level ^ delayed) << 1) - 1;
}
@@ -124,7 +119,7 @@ bool CAX25Demodulator::process(const q15_t* samples, uint8_t length, CAX25Frame&
if (result) {
// Copy the frame data.
::memcpy(frame.m_data, m_frame.m_data, AX25_MAX_PACKET_LEN);
frame.m_length = frame.m_length;
frame.m_length = m_frame.m_length;
frame.m_fcs = m_frame.m_fcs;
m_frame.m_length = 0U;
}
@@ -160,7 +155,7 @@ bool CAX25Demodulator::PLL(bool input)
{
bool sample = false;
if (input != m_pllLast or m_pllBits > 16U) {
if (input != m_pllLast || m_pllBits > 16U) {
// Record transition.
m_pllLast = input;
@@ -214,9 +209,11 @@ bool CAX25Demodulator::HDLC(bool b)
switch (m_hdlcBuffer) {
case 0x7E:
if (m_frame.m_length > 2U) {
if (m_frame.m_length >= 13U) {
result = m_frame.checkCRC();
if (!result)
m_frame.m_length = 0U;
} else {
m_frame.m_length = 0U;
}
m_hdlcState = AX25_SYNC;