Add the twist processing to the AX25 RX.

AX25Demodulator.cpp

@@ -53,10 +53,9 @@ 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(q15_t* coeffs, uint16_t length) :
+CAX25Demodulator::CAX25Demodulator(int8_t n) :
 m_frame(),
-m_audioFilter(),
+m_twist(n),
-m_audioState(),
 m_lpfFilter(),
 m_lpfState(),
 m_delayLine(NULL),
@@ -75,10 +74,6 @@ m_hdlcState(AX25_IDLE)
 {
   m_delayLine = new bool[DELAY_LEN];
 
-  m_audioFilter.numTaps = length;
-  m_audioFilter.pState  = m_audioState;
-  m_audioFilter.pCoeffs = coeffs;
-
   m_lpfFilter.numTaps = LPF_FILTER_LEN;
   m_lpfFilter.pState  = m_lpfState;
   m_lpfFilter.pCoeffs = LPF_FILTER_COEFFS;
@@ -93,7 +88,7 @@ bool CAX25Demodulator::process(q15_t* samples, uint8_t length, CAX25Frame& frame
   bool result = false;
 
   q15_t fa[RX_BLOCK_SIZE];
-  ::arm_fir_fast_q15(&m_audioFilter, samples, fa, RX_BLOCK_SIZE);
+  m_twist.process(samples, fa, RX_BLOCK_SIZE);
 
   int16_t buffer[RX_BLOCK_SIZE];
   for (uint8_t i = 0; i < length; i++) {
@@ -263,3 +258,8 @@ bool CAX25Demodulator::HDLC(bool b)
   return false;
 }
 
+void CAX25Demodulator::setTwist(int8_t n)
+{
+  m_twist.setTwist(n);
+}
+

AX25Demodulator.h

@@ -22,6 +22,7 @@
 #include "Config.h"
 
 #include "AX25Frame.h"
+#include "AX25Twist.h"
 
 enum AX25_STATE {
   AX25_IDLE,
@@ -31,14 +32,15 @@ enum AX25_STATE {
 
 class CAX25Demodulator {
 public:
-  CAX25Demodulator(q15_t* coeffs, uint16_t length);
+  CAX25Demodulator(int8_t n);
 
   bool process(q15_t* samples, uint8_t length, CAX25Frame& frame);
 
+  void setTwist(int8_t n);
+
 private:
   CAX25Frame           m_frame;
-  arm_fir_instance_q15 m_audioFilter;
+  CAX25Twist           m_twist;
-  q15_t                m_audioState[40U];   // NoTaps + BlockSize - 1, 9 + 20 - 1 plus some spare
   arm_fir_instance_q15 m_lpfFilter;
   q15_t                m_lpfState[120U];    // NoTaps + BlockSize - 1, 96 + 20 - 1 plus some spare
   bool*                m_delayLine;

AX25RX.cpp

@@ -20,252 +20,6 @@
 #include "Globals.h"
 #include "AX25RX.h"
 
-// 1200Hz = -12dB, 2200Hz = 0dB; 3381Hz cutoff; cosine.
-q15_t dB12[] = {
-  176,
-  -812,
-  -3916,
-  -7586,
-  23536,
-  -7586,
-  -3916,
-  -812,
-  176
-};
-
-// 1200Hz = -11dB, 2200Hz = 0dB; 3258Hz cutoff; cosine.
-q15_t dB11[] = {
-  121,
-  -957,
-  -3959,
-  -7383,
-  23871,
-  -7383,
-  -3959,
-  -957,
-  121
-};
-
-// 1200Hz = -10dB, 2200Hz = 0dB; 3118Hz cutoff; cosine.
-q15_t dB10[] = {
-  56,
-  -1110,
-  -3987,
-  -7141,
-  24254,
-  -7141,
-  -3987,
-  -1110,
-  56
-};
-
-// 1200Hz = -9dB, 2200Hz = 0dB; 2959Hz cutoff; cosine.
-q15_t dB9[] = {
-  -19,
-  -1268,
-  -3994,
-  -6856,
-  24688,
-  -6856,
-  -3994,
-  -1268,
-  -19
-};
-
-// 1200Hz = -8dB, 2200Hz = 0dB; 2778Hz cutoff; cosine.
-q15_t dB8[] = {
-  -104,
-  -1424,
-  -3968,
-  -6516,
-  25182,
-  -6516,
-  -3968,
-  -1424,
-  -104
-};
-
-// 1200Hz = -7dB, 2200Hz = 0dB; 2573Hz cutoff; cosine.
-q15_t dB7[] = {
-  -196,
-  -1565,
-  -3896,
-  -6114,
-  25742,
-  -6114,
-  -3896,
-  -1565,
-  -196
-};
-
-// 1200Hz = -6dB, 2200Hz = 0dB; 2343Hz cutoff; cosine.
-q15_t dB6[] = {
-  -288,
-  -1676,
-  -3761,
-  -5642,
-  26370,
-  -5642,
-  -3761,
-  -1676,
-  -288
-};
-
-// 1200Hz = -5dB, 2200Hz = 0dB; 2085Hz cutoff; cosine.
-q15_t dB5[] = {
-  -370,
-  -1735,
-  -3545,
-  -5088,
-  27075,
-  -5088,
-  -3545,
-  -1735,
-  -370
-};
-
-// 1200Hz = -4dB, 2200Hz = 0dB; 1790Hz cutoff; cosine.
-q15_t dB4[] = {
-  -432,
-  -1715,
-  -3220,
-  -4427,
-  27880,
-  -4427,
-  -3220,
-  -1715,
-  -432
-};
-
-// 1200Hz = -3dB, 2200Hz = 0dB; 1456Hz cutoff; cosine.
-q15_t dB3[] = {
-  -452,
-  -1582,
-  -2759,
-  -3646,
-  28792,
-  -3646,
-  -2759,
-  -1582,
-  -452
-};
-
-// 1200Hz = -2dB, 2200Hz = 0dB; 1070Hz cutoff; cosine.
-q15_t dB2[] = {
-  -408,
-  -1295,
-  -2123,
-  -2710,
-  29846,
-  -2710,
-  -2123,
-  -1295,
-  -408
-};
-
-// 1200Hz = -1dB, 2200Hz = 0dB; 605Hz cutoff; cosine.
-q15_t dB1[] = {
-  -268,
-  -795,
-  -1244,
-  -1546,
-  31116,
-  -1546,
-  -1244,
-  -795,
-  -268
-};
-
-q15_t dB0[] = {
-  0,
-  0,
-  0,
-  0,
-  32767,
-  0,
-  0,
-  0,
-  0,
-};
-
-// 1200Hz = 0dB, 2200Hz = -1dB; 4130Hz cutoff; cosine.
-q15_t dB_1[] = {
-  -419,
-  -177,
-  3316,
-  8650,
-  11278,
-  8650,
-  3316,
-  -177,
-  -419
-};
-
-// 1200Hz = 0dB, 2200Hz = -2dB; 3190Hz cutoff; cosine.
-q15_t dB_2[] = {
-  -90,
-  1033,
-  3975,
-  7267,
-  8711,
-  7267,
-  3975,
-  1033,
-  -90
-};
-
-// 1200Hz = 0dB, 2200Hz = -3dB; 2330Hz cutoff; cosine.
-q15_t dB_3[] = {
-  292,
-  1680,
-  3752,
-  5615,
-  6362,
-  5615,
-  3752,
-  1680,
-  292
-};
-
-// 1200Hz = 0dB, 2200Hz = -4dB; 2657Hz cutoff; boxcar.
-q15_t dB_4[] = {
-  917,
-  3024,
-  5131,
-  6684,
-  7255,
-  6684,
-  5131,
-  3024,
-  917
-};
-
-// 1200Hz = 0dB, 2200Hz = -5dB; 2360Hz cutoff; boxcar.
-q15_t dB_5[] = {
-  1620,
-  3339,
-  4925,
-  6042,
-  6444,
-  6042,
-  4925,
-  3339,
-  1620
-};
-
-// 1200Hz = 0dB, 2200Hz = -6dB; 2067Hz cutoff; boxcar.
-q15_t dB_6[] = {
-  2161,
-  3472,
-  4605,
-  5373,
-  5644,
-  5373,
-  4605,
-  3472,
-  2161
-};
-
 /*
  * Generated with Scipy Filter, 152 coefficients, 1100-2300Hz bandpass,
  * Hann window, starting and ending 0 value coefficients removed.
@@ -306,9 +60,9 @@ q15_t FILTER_COEFFS[] = {
 CAX25RX::CAX25RX() :
 m_filter(),
 m_state(),
-m_demod1(dB3, 9U),
+m_demod1(3),
-m_demod2(dB6, 9U),
+m_demod2(6),
-m_demod3(dB9, 9U),
+m_demod3(9),
 m_lastFCS(0U)
 {
   m_filter.numTaps = FILTER_LEN;
@@ -346,3 +100,10 @@ void CAX25RX::samples(q15_t* samples, uint8_t length)
   }
 }
 
+void CAX25RX::setParams(int8_t twist)
+{
+  m_demod1.setTwist(twist - 3);
+  m_demod2.setTwist(twist);
+  m_demod3.setTwist(twist + 3);
+}
+

AX25Twist.cpp

@@ -0,0 +1,311 @@
+/*
+ *   Copyright (C) 2020 by Jonathan Naylor G4KLX
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include "Config.h"
+#include "Globals.h"
+#include "AX25Twist.h"
+
+// 1200Hz = -12dB, 2200Hz = 0dB; 3381Hz cutoff; cosine.
+q15_t dB12[] = {
+  176,
+  -812,
+  -3916,
+  -7586,
+  23536,
+  -7586,
+  -3916,
+  -812,
+  176
+};
+
+// 1200Hz = -11dB, 2200Hz = 0dB; 3258Hz cutoff; cosine.
+q15_t dB11[] = {
+  121,
+  -957,
+  -3959,
+  -7383,
+  23871,
+  -7383,
+  -3959,
+  -957,
+  121
+};
+
+// 1200Hz = -10dB, 2200Hz = 0dB; 3118Hz cutoff; cosine.
+q15_t dB10[] = {
+  56,
+  -1110,
+  -3987,
+  -7141,
+  24254,
+  -7141,
+  -3987,
+  -1110,
+  56
+};
+
+// 1200Hz = -9dB, 2200Hz = 0dB; 2959Hz cutoff; cosine.
+q15_t dB9[] = {
+  -19,
+  -1268,
+  -3994,
+  -6856,
+  24688,
+  -6856,
+  -3994,
+  -1268,
+  -19
+};
+
+// 1200Hz = -8dB, 2200Hz = 0dB; 2778Hz cutoff; cosine.
+q15_t dB8[] = {
+  -104,
+  -1424,
+  -3968,
+  -6516,
+  25182,
+  -6516,
+  -3968,
+  -1424,
+  -104
+};
+
+// 1200Hz = -7dB, 2200Hz = 0dB; 2573Hz cutoff; cosine.
+q15_t dB7[] = {
+  -196,
+  -1565,
+  -3896,
+  -6114,
+  25742,
+  -6114,
+  -3896,
+  -1565,
+  -196
+};
+
+// 1200Hz = -6dB, 2200Hz = 0dB; 2343Hz cutoff; cosine.
+q15_t dB6[] = {
+  -288,
+  -1676,
+  -3761,
+  -5642,
+  26370,
+  -5642,
+  -3761,
+  -1676,
+  -288
+};
+
+// 1200Hz = -5dB, 2200Hz = 0dB; 2085Hz cutoff; cosine.
+q15_t dB5[] = {
+  -370,
+  -1735,
+  -3545,
+  -5088,
+  27075,
+  -5088,
+  -3545,
+  -1735,
+  -370
+};
+
+// 1200Hz = -4dB, 2200Hz = 0dB; 1790Hz cutoff; cosine.
+q15_t dB4[] = {
+  -432,
+  -1715,
+  -3220,
+  -4427,
+  27880,
+  -4427,
+  -3220,
+  -1715,
+  -432
+};
+
+// 1200Hz = -3dB, 2200Hz = 0dB; 1456Hz cutoff; cosine.
+q15_t dB3[] = {
+  -452,
+  -1582,
+  -2759,
+  -3646,
+  28792,
+  -3646,
+  -2759,
+  -1582,
+  -452
+};
+
+// 1200Hz = -2dB, 2200Hz = 0dB; 1070Hz cutoff; cosine.
+q15_t dB2[] = {
+  -408,
+  -1295,
+  -2123,
+  -2710,
+  29846,
+  -2710,
+  -2123,
+  -1295,
+  -408
+};
+
+// 1200Hz = -1dB, 2200Hz = 0dB; 605Hz cutoff; cosine.
+q15_t dB1[] = {
+  -268,
+  -795,
+  -1244,
+  -1546,
+  31116,
+  -1546,
+  -1244,
+  -795,
+  -268
+};
+
+q15_t dB0[] = {
+  0,
+  0,
+  0,
+  0,
+  32767,
+  0,
+  0,
+  0,
+  0,
+};
+
+// 1200Hz = 0dB, 2200Hz = -1dB; 4130Hz cutoff; cosine.
+q15_t dB_1[] = {
+  -419,
+  -177,
+  3316,
+  8650,
+  11278,
+  8650,
+  3316,
+  -177,
+  -419
+};
+
+// 1200Hz = 0dB, 2200Hz = -2dB; 3190Hz cutoff; cosine.
+q15_t dB_2[] = {
+  -90,
+  1033,
+  3975,
+  7267,
+  8711,
+  7267,
+  3975,
+  1033,
+  -90
+};
+
+// 1200Hz = 0dB, 2200Hz = -3dB; 2330Hz cutoff; cosine.
+q15_t dB_3[] = {
+  292,
+  1680,
+  3752,
+  5615,
+  6362,
+  5615,
+  3752,
+  1680,
+  292
+};
+
+// 1200Hz = 0dB, 2200Hz = -4dB; 2657Hz cutoff; boxcar.
+q15_t dB_4[] = {
+  917,
+  3024,
+  5131,
+  6684,
+  7255,
+  6684,
+  5131,
+  3024,
+  917
+};
+
+// 1200Hz = 0dB, 2200Hz = -5dB; 2360Hz cutoff; boxcar.
+q15_t dB_5[] = {
+  1620,
+  3339,
+  4925,
+  6042,
+  6444,
+  6042,
+  4925,
+  3339,
+  1620
+};
+
+// 1200Hz = 0dB, 2200Hz = -6dB; 2067Hz cutoff; boxcar.
+q15_t dB_6[] = {
+  2161,
+  3472,
+  4605,
+  5373,
+  5644,
+  5373,
+  4605,
+  3472,
+  2161
+};
+
+q15_t* coeffs[] = {
+  dB12,
+  dB11,
+  dB10,
+  dB9,
+  dB8,
+  dB7,
+  dB6,
+  dB5,
+  dB4,
+  dB3,
+  dB2,
+  dB1,
+  dB0,
+  dB_1,
+  dB_2,
+  dB_3,
+  dB_4,
+  dB_5,
+  dB_6
+};
+
+CAX25Twist::CAX25Twist(int8_t n) :
+m_filter(),
+m_state()
+{
+  setTwist(n);
+}
+
+void CAX25Twist::process(q15_t* in, q15_t* out, uint8_t length)
+{
+  ::arm_fir_fast_q15(&m_filter, in, out, length);
+}
+
+void CAX25Twist::setTwist(int8_t n)
+{
+  uint8_t twist = uint8_t(n + 6);
+
+  m_filter.numTaps = 9;
+  m_filter.pState  = m_state;
+  m_filter.pCoeffs = coeffs[twist];
+}
+

AX25Twist.h

@@ -0,0 +1,39 @@
+/*
+ *   Copyright (C) 2020 by Jonathan Naylor G4KLX
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#if !defined(AX25Twist_H)
+#define  AX25Twist_H
+
+#include "Config.h"
+
+
+class CAX25Twist {
+public:
+  CAX25Twist(int8_t n);
+
+  void process(q15_t* in, q15_t* out, uint8_t length);
+
+  void setTwist(int8_t n);
+
+private:
+  arm_fir_instance_q15 m_filter;
+  q15_t                m_state[40U];   // NoTaps + BlockSize - 1, 9 + 20 - 1 plus some spare
+};
+
+#endif
+