Merge branch 'master' into AX25

AX25Defines.h

@@ -0,0 +1,36 @@
+/*
+ *   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(AX25DEFINES_H)
+#define  AX25DEFINES_H
+
+const uint8_t AX25_RADIO_SYMBOL_LENGTH = 20U;      // At 24 kHz sample rate
+
+const uint8_t AX25_FRAME_START = 0x7EU;
+const uint8_t AX25_FRAME_END   = 0x7EU;
+const uint8_t AX25_FRAME_ABORT = 0xFEU;
+
+const uint8_t AX25_MAX_ONES    = 5U;
+
+const uint16_t AX25_MIN_FRAME_LENGTH = 17U;        // Callsign (7) + Callsign (7) + Control (1) + Checksum (2)
+
+const uint16_t AX25_MAX_FRAME_LENGTH = 330U;       // Callsign (7) + Callsign (7) + 8 Digipeaters (56) +
+                                                   // Control (1) + PID (1) + Data (256) + Checksum (2)
+
+#endif
+

AX25Demodulator.cpp

@@ -0,0 +1,266 @@
+/*
+ *   Copyright (C) 2020 by Jonathan Naylor G4KLX
+ *   Copyright 2015-2019 Mobilinkd LLC <[email protected]>
+ *
+ *   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 "AX25Demodulator.h"
+#include "AX25Defines.h"
+
+const float32_t SAMPLE_RATE = 24000.0F;
+const float32_t SYMBOL_RATE = 1200.0F;
+
+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;
+
+const uint32_t LPF_FILTER_LEN = 96U;
+
+q15_t LPF_FILTER_COEFFS[] = {
+     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.
+// scipy.signal:
+//      loop_coeffs = firwin(9, [64.0/(1200/2)], width = None,
+//          pass_zero = True, scale = True, window='hann')
+//
+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(int8_t n) :
+m_frame(),
+m_twist(n),
+m_lpfFilter(),
+m_lpfState(),
+m_delayLine(NULL),
+m_delayPos(0U),
+m_nrziState(false),
+m_pllFilter(),
+m_pllState(),
+m_pllLast(false),
+m_pllBits(1U),
+m_pllCount(0.0F),
+m_hdlcOnes(0U),
+m_hdlcFlag(false),
+m_hdlcBuffer(0U),
+m_hdlcBits(0U),
+m_hdlcState(AX25_IDLE)
+{
+  m_delayLine = new bool[DELAY_LEN];
+
+  m_lpfFilter.numTaps = LPF_FILTER_LEN;
+  m_lpfFilter.pState  = m_lpfState;
+  m_lpfFilter.pCoeffs = LPF_FILTER_COEFFS;
+
+  m_pllFilter.numTaps = PLL_FILTER_LEN;
+  m_pllFilter.pState  = m_pllState;
+  m_pllFilter.pCoeffs = PLL_FILTER_COEFFS;
+}
+
+bool CAX25Demodulator::process(q15_t* samples, uint8_t length, CAX25Frame& frame)
+{
+  bool result = false;
+
+  q15_t 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++) {
+      bool   level = (fa[i] >= 0);
+      bool delayed = delay(level);
+      buffer[i] = (int16_t(level ^ delayed) << 1) - 1;
+  }
+
+  q15_t fc[RX_BLOCK_SIZE];
+  ::arm_fir_fast_q15(&m_lpfFilter, buffer, fc, RX_BLOCK_SIZE);
+
+  for (uint8_t i = 0; i < length; i++) {
+    bool bit = fc[i] >= 0;
+    bool sample = PLL(bit);
+
+    if (sample) {
+      // We will only ever get one frame because there are
+      // not enough bits in a block for more than one.
+      if (result) {
+        HDLC(NRZI(bit));
+      } else {
+        result = HDLC(NRZI(bit));
+        if (result) {
+          // Copy the frame data.
+          ::memcpy(frame.m_data, m_frame.m_data, AX25_MAX_PACKET_LEN);
+          frame.m_length = m_frame.m_length;
+          frame.m_fcs    = m_frame.m_fcs;
+          m_frame.m_length = 0U;
+        }
+      }
+    }
+  }
+
+  return result;
+}
+
+bool CAX25Demodulator::delay(bool b)
+{
+  bool r = m_delayLine[m_delayPos];
+
+  m_delayLine[m_delayPos++] = b;
+
+  if (m_delayPos >= DELAY_LEN)
+    m_delayPos = 0U;
+
+  return r;
+}
+
+bool CAX25Demodulator::NRZI(bool b)
+{
+  bool result = (b == m_nrziState);
+
+  m_nrziState = b;
+
+  return result;
+}
+
+bool CAX25Demodulator::PLL(bool input)
+{
+  bool sample = false;
+		
+  if (input != m_pllLast || m_pllBits > 16U) {
+    // Record transition.
+    m_pllLast = input;
+
+    if (m_pllCount > PLL_LIMIT)
+      m_pllCount -= SAMPLES_PER_SYMBOL;
+
+    float32_t offset = m_pllCount / float32_t(m_pllBits);
+    float32_t jitter;
+    ::arm_fir_f32(&m_pllFilter, &offset, &jitter, 1U);
+
+    m_pllCount -= jitter / 2.0F;
+    m_pllBits = 1U;
+  } else {
+    if (m_pllCount > PLL_LIMIT) {
+      sample = true;
+      m_pllCount -= SAMPLES_PER_SYMBOL;
+      m_pllBits++;
+    }
+  }
+
+  m_pllCount += 1.0F;
+
+  return sample;
+}
+
+bool CAX25Demodulator::HDLC(bool b)
+{
+  if (m_hdlcOnes == AX25_MAX_ONES) {
+    if (b) {
+      // flag byte
+      m_hdlcFlag = true;
+    } else {
+      // bit stuffing...
+      m_hdlcFlag = false;
+      m_hdlcOnes = 0U;
+      return false;
+    }
+  }
+
+  m_hdlcBuffer >>= 1;
+  m_hdlcBuffer |= b ? 128U : 0U;
+  m_hdlcBits++;                      // Free-running until Sync byte.
+
+  if (b)
+    m_hdlcOnes++;
+  else
+    m_hdlcOnes = 0U;
+
+  if (m_hdlcFlag) {
+    bool result = false;
+
+    switch (m_hdlcBuffer) {
+      case AX25_FRAME_END:
+        if (m_frame.m_length >= AX25_MIN_FRAME_LENGTH) {
+          result = m_frame.checkCRC();
+          if (!result)
+              m_frame.m_length = 0U;
+        } else {
+            m_frame.m_length = 0U;
+        }
+        m_hdlcState = AX25_SYNC;
+        m_hdlcFlag = false;
+        m_hdlcBits = 0U;
+        break;
+
+      case AX25_FRAME_ABORT:
+        // Frame aborted
+        m_frame.m_length = 0U;
+        m_hdlcState = AX25_IDLE;
+        m_hdlcFlag = false;
+        m_hdlcBits = 0U;
+        break;
+
+      default:
+        break;
+    }
+
+    return result;
+  }
+
+  switch (m_hdlcState) {
+    case AX25_IDLE:
+      break;
+
+    case AX25_SYNC:
+      if (m_hdlcBits == 8U) {    // 8th bit.
+        // Start of frame data.
+        m_hdlcState = AX25_RECEIVE;
+        m_frame.append(m_hdlcBuffer);
+        m_hdlcBits = 0U;
+      }
+      break;
+
+    case AX25_RECEIVE:
+      if (m_hdlcBits == 8U) {    // 8th bit.
+        m_frame.append(m_hdlcBuffer);
+        m_hdlcBits = 0U;
+      }
+      break;
+
+    default:
+      break;
+  }
+
+  return false;
+}
+
+void CAX25Demodulator::setTwist(int8_t n)
+{
+  m_twist.setTwist(n);
+}
+

AX25Demodulator.h

@@ -0,0 +1,67 @@
+/*
+ *   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(AX25Demodulator_H)
+#define  AX25Demodulator_H
+
+#include "Config.h"
+
+#include "AX25Frame.h"
+#include "AX25Twist.h"
+
+enum AX25_STATE {
+  AX25_IDLE,
+  AX25_SYNC,
+  AX25_RECEIVE
+};
+
+class CAX25Demodulator {
+public:
+  CAX25Demodulator(int8_t n);
+
+  bool process(q15_t* samples, uint8_t length, CAX25Frame& frame);
+
+  void setTwist(int8_t n);
+
+private:
+  CAX25Frame           m_frame;
+  CAX25Twist           m_twist;
+  arm_fir_instance_q15 m_lpfFilter;
+  q15_t                m_lpfState[120U];    // NoTaps + BlockSize - 1, 96 + 20 - 1 plus some spare
+  bool*                m_delayLine;
+  uint16_t             m_delayPos;
+  bool                 m_nrziState;
+  arm_fir_instance_f32 m_pllFilter;
+  float32_t            m_pllState[20U];     // NoTaps + BlockSize - 1, 7 + 1 - 1 plus some spare
+  bool                 m_pllLast;
+  uint8_t              m_pllBits;
+  float32_t            m_pllCount;
+  uint16_t             m_hdlcOnes;
+  bool                 m_hdlcFlag;
+  uint16_t             m_hdlcBuffer;
+  uint16_t             m_hdlcBits;
+  AX25_STATE           m_hdlcState;
+
+  bool delay(bool b);
+  bool NRZI(bool b);
+  bool PLL(bool b);
+  bool HDLC(bool b);
+};
+
+#endif
+

AX25Frame.cpp

@@ -0,0 +1,122 @@
+/*
+ *   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 "AX25Frame.h"
+
+const uint16_t CCITT_TABLE[] = {
+	0x0000,0x1189,0x2312,0x329b,0x4624,0x57ad,0x6536,0x74bf,
+	0x8c48,0x9dc1,0xaf5a,0xbed3,0xca6c,0xdbe5,0xe97e,0xf8f7,
+	0x1081,0x0108,0x3393,0x221a,0x56a5,0x472c,0x75b7,0x643e,
+	0x9cc9,0x8d40,0xbfdb,0xae52,0xdaed,0xcb64,0xf9ff,0xe876,
+	0x2102,0x308b,0x0210,0x1399,0x6726,0x76af,0x4434,0x55bd,
+	0xad4a,0xbcc3,0x8e58,0x9fd1,0xeb6e,0xfae7,0xc87c,0xd9f5,
+	0x3183,0x200a,0x1291,0x0318,0x77a7,0x662e,0x54b5,0x453c,
+	0xbdcb,0xac42,0x9ed9,0x8f50,0xfbef,0xea66,0xd8fd,0xc974,
+	0x4204,0x538d,0x6116,0x709f,0x0420,0x15a9,0x2732,0x36bb,
+	0xce4c,0xdfc5,0xed5e,0xfcd7,0x8868,0x99e1,0xab7a,0xbaf3,
+	0x5285,0x430c,0x7197,0x601e,0x14a1,0x0528,0x37b3,0x263a,
+	0xdecd,0xcf44,0xfddf,0xec56,0x98e9,0x8960,0xbbfb,0xaa72,
+	0x6306,0x728f,0x4014,0x519d,0x2522,0x34ab,0x0630,0x17b9,
+	0xef4e,0xfec7,0xcc5c,0xddd5,0xa96a,0xb8e3,0x8a78,0x9bf1,
+	0x7387,0x620e,0x5095,0x411c,0x35a3,0x242a,0x16b1,0x0738,
+	0xffcf,0xee46,0xdcdd,0xcd54,0xb9eb,0xa862,0x9af9,0x8b70,
+	0x8408,0x9581,0xa71a,0xb693,0xc22c,0xd3a5,0xe13e,0xf0b7,
+	0x0840,0x19c9,0x2b52,0x3adb,0x4e64,0x5fed,0x6d76,0x7cff,
+	0x9489,0x8500,0xb79b,0xa612,0xd2ad,0xc324,0xf1bf,0xe036,
+	0x18c1,0x0948,0x3bd3,0x2a5a,0x5ee5,0x4f6c,0x7df7,0x6c7e,
+	0xa50a,0xb483,0x8618,0x9791,0xe32e,0xf2a7,0xc03c,0xd1b5,
+	0x2942,0x38cb,0x0a50,0x1bd9,0x6f66,0x7eef,0x4c74,0x5dfd,
+	0xb58b,0xa402,0x9699,0x8710,0xf3af,0xe226,0xd0bd,0xc134,
+	0x39c3,0x284a,0x1ad1,0x0b58,0x7fe7,0x6e6e,0x5cf5,0x4d7c,
+	0xc60c,0xd785,0xe51e,0xf497,0x8028,0x91a1,0xa33a,0xb2b3,
+	0x4a44,0x5bcd,0x6956,0x78df,0x0c60,0x1de9,0x2f72,0x3efb,
+	0xd68d,0xc704,0xf59f,0xe416,0x90a9,0x8120,0xb3bb,0xa232,
+	0x5ac5,0x4b4c,0x79d7,0x685e,0x1ce1,0x0d68,0x3ff3,0x2e7a,
+	0xe70e,0xf687,0xc41c,0xd595,0xa12a,0xb0a3,0x8238,0x93b1,
+	0x6b46,0x7acf,0x4854,0x59dd,0x2d62,0x3ceb,0x0e70,0x1ff9,
+	0xf78f,0xe606,0xd49d,0xc514,0xb1ab,0xa022,0x92b9,0x8330,
+	0x7bc7,0x6a4e,0x58d5,0x495c,0x3de3,0x2c6a,0x1ef1,0x0f78 };
+
+CAX25Frame::CAX25Frame(const uint8_t* data, uint16_t length) :
+m_data(),
+m_length(0U),
+m_fcs(0U)
+{
+  for (uint16_t i = 0U; i < length && i < (AX25_MAX_PACKET_LEN - 2U); i++)
+    m_data[m_length++] = data[i];
+}
+
+CAX25Frame::CAX25Frame() :
+m_data(),
+m_length(0U),
+m_fcs(0U)
+{
+}
+
+bool CAX25Frame::append(uint16_t c)
+{
+  if (m_length == AX25_MAX_PACKET_LEN)
+    return false;
+
+  m_data[m_length++] = uint8_t(c);
+
+  return true;
+}
+
+bool CAX25Frame::checkCRC()
+{
+  union {
+    uint16_t crc16;
+    uint8_t  crc8[2U];
+  };
+
+  crc16 = 0xFFFFU;
+  for (uint16_t i = 0U; i < (m_length - 2U); i++)
+    crc16 = uint16_t(crc8[1U]) ^ CCITT_TABLE[crc8[0U] ^ m_data[i]];
+
+  crc16 = ~crc16;
+
+  if (crc8[0U] == m_data[m_length - 2U] && crc8[1U] == m_data[m_length - 1U]) {
+    m_fcs = crc16;
+    return true;
+  } else {
+    return false;
+  }
+}
+
+void CAX25Frame::addCRC()
+{
+  union {
+    uint16_t crc16;
+    uint8_t  crc8[2U];
+  };
+
+  crc16 = 0xFFFFU;
+  for (uint16_t i = 0U; i < m_length; i++)
+    crc16 = uint16_t(crc8[1U]) ^ CCITT_TABLE[crc8[0U] ^ m_data[i]];
+
+  crc16 = ~crc16;
+
+  m_fcs = crc16;
+
+  m_data[m_length++] = crc8[0U];
+  m_data[m_length++] = crc8[1U];
+}
+

AX25Frame.h

@@ -0,0 +1,43 @@
+/*
+ *   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(AX25Frame_H)
+#define  AX25Frame_H
+
+#include "Config.h"
+
+const uint16_t AX25_MAX_PACKET_LEN = 300U;
+
+class CAX25Frame {
+public:
+  CAX25Frame(const uint8_t* data, uint16_t length);
+  CAX25Frame();
+
+  bool append(uint16_t c);
+
+  bool checkCRC();
+
+  void addCRC();
+
+  uint8_t  m_data[AX25_MAX_PACKET_LEN];
+  uint16_t m_length;
+  uint16_t m_fcs;
+};
+
+#endif
+

AX25RX.cpp

@@ -0,0 +1,120 @@
+/*
+ *   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 "AX25RX.h"
+
+/*
+ * Generated with Scipy Filter, 152 coefficients, 1100-2300Hz bandpass,
+ * Hann window, starting and ending 0 value coefficients removed.
+ *
+ * np.array(
+ *  firwin2(152,
+ *      [
+ *          0.0,
+ *          1000.0/(sample_rate/2),
+ *          1100.0/(sample_rate/2),
+ *          2350.0/(sample_rate/2),
+ *          2500.0/(sample_rate/2),
+ *          1.0
+ *      ],
+ *      [0,0,1,1,0,0],
+ *      antisymmetric = False,
+ *      window='hann') * 32768,
+ *  dtype=int)[10:-10]
+ */
+const uint32_t FILTER_LEN = 132;
+q15_t FILTER_COEFFS[] = {
+      0,     5,    12,    18,    21,   19,   11,    -2,   -15,   -25,
+    -27,   -21,   -11,    -3,    -5,  -19,  -43,   -69,   -83,   -73,
+    -35,    27,    98,   155,   180,  163,  109,    39,   -20,   -45,
+    -26,    23,    74,    89,    39,  -81, -247,  -407,  -501,  -480,
+   -334,   -92,   175,   388,   479,  429,  275,    99,     5,    68,
+    298,   626,   913,   994,   740,  115, -791, -1770, -2544, -2847,
+  -2509, -1527,   -76,  1518,  2875, 3653, 3653,  2875,  1518,   -76,
+  -1527, -2509, -2847, -2544, -1770, -791,  115,   740,   994,   913,
+    626,   298,    68,     5,    99,  275,  429,   479,   388,   175,
+    -92,  -334,  -480,  -501,  -407, -247,  -81,    39,    89,    74,
+     23,   -26,   -45,   -20,    39,  109,  163,   180,   155,    98,
+     27,   -35,   -73,   -83,   -69,  -43,  -19,    -5,    -3,   -11,
+    -21,   -27,   -25,   -15,    -2,   11,   19,    21,    18,    12,
+      5,     0
+};
+
+CAX25RX::CAX25RX() :
+m_filter(),
+m_state(),
+m_demod1(3),
+m_demod2(6),
+m_demod3(9),
+m_lastFCS(0U),
+m_count(0U)
+{
+  m_filter.numTaps = FILTER_LEN;
+  m_filter.pState  = m_state;
+  m_filter.pCoeffs = FILTER_COEFFS;
+}
+
+void CAX25RX::samples(q15_t* samples, uint8_t length)
+{
+  q15_t output[RX_BLOCK_SIZE];
+  ::arm_fir_fast_q15(&m_filter, samples, output, RX_BLOCK_SIZE);
+
+  m_count++;
+
+  CAX25Frame frame;
+
+  bool ret = m_demod1.process(output, length, frame);
+  if (ret) {
+    if (frame.m_fcs != m_lastFCS || m_count > 2U) {
+      m_lastFCS = frame.m_fcs;
+      m_count   = 0U;
+      serial.writeAX25Data(frame.m_data, frame.m_length - 2U);
+    }
+    DEBUG1("Decoder 1 reported");
+  }
+
+  ret = m_demod2.process(output, length, frame);
+  if (ret) {
+    if (frame.m_fcs != m_lastFCS || m_count > 2U) {
+      m_lastFCS = frame.m_fcs;
+      m_count   = 0U;
+      serial.writeAX25Data(frame.m_data, frame.m_length - 2U);
+    }
+    DEBUG1("Decoder 2 reported");
+  }
+
+  ret = m_demod3.process(output, length, frame);
+  if (ret) {
+    if (frame.m_fcs != m_lastFCS || m_count > 2U) {
+      m_lastFCS = frame.m_fcs;
+      m_count   = 0U;
+      serial.writeAX25Data(frame.m_data, frame.m_length - 2U);
+    }
+    DEBUG1("Decoder 3 reported");
+  }
+}
+
+void CAX25RX::setParams(int8_t twist)
+{
+  m_demod1.setTwist(twist - 3);
+  m_demod2.setTwist(twist);
+  m_demod3.setTwist(twist + 3);
+}
+

AX25RX.h

@@ -0,0 +1,45 @@
+/*
+ *   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(AX25RX_H)
+#define  AX25RX_H
+
+#include "Config.h"
+
+#include "AX25Demodulator.h"
+
+class CAX25RX {
+public:
+  CAX25RX();
+
+  void samples(q15_t* samples, uint8_t length);
+
+  void setParams(int8_t twist);
+
+private:
+  arm_fir_instance_q15 m_filter;
+  q15_t                m_state[160U];    // NoTaps + BlockSize - 1, 132 + 20 - 1 plus some spare
+  CAX25Demodulator     m_demod1;
+  CAX25Demodulator     m_demod2;
+  CAX25Demodulator     m_demod3;
+  uint16_t             m_lastFCS;
+  uint32_t             m_count;
+};
+
+#endif
+

AX25TX.cpp

@@ -0,0 +1,180 @@
+/*
+ *   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 "AX25TX.h"
+
+#include "AX25Defines.h"
+#include "AX25Frame.h"
+
+
+const uint8_t START_FLAG[] = { AX25_FRAME_START };
+const uint8_t END_FLAG[]   = { AX25_FRAME_END };
+
+const uint8_t BIT_MASK_TABLE1[] = { 0x80U, 0x40U, 0x20U, 0x10U, 0x08U, 0x04U, 0x02U, 0x01U };
+
+#define WRITE_BIT1(p,i,b) p[(i)>>3] = (b) ? (p[(i)>>3] | BIT_MASK_TABLE1[(i)&7]) : (p[(i)>>3] & ~BIT_MASK_TABLE1[(i)&7])
+#define READ_BIT1(p,i)    (p[(i)>>3] & BIT_MASK_TABLE1[(i)&7])
+
+const uint8_t BIT_MASK_TABLE2[] = { 0x01U, 0x02U, 0x04U, 0x08U, 0x10U, 0x20U, 0x40U, 0x80U };
+
+#define WRITE_BIT2(p,i,b) p[(i)>>3] = (b) ? (p[(i)>>3] | BIT_MASK_TABLE2[(i)&7]) : (p[(i)>>3] & ~BIT_MASK_TABLE2[(i)&7])
+#define READ_BIT2(p,i)    (p[(i)>>3] & BIT_MASK_TABLE2[(i)&7])
+
+const uint16_t AUDIO_TABLE_LEN = 120U;
+
+const q15_t AUDIO_TABLE_DATA[] = {
+  0, 214, 428, 641, 851, 1060, 1265, 1468, 1666, 1859, 2048, 2230, 2407, 2577, 2740, 2896, 3043, 3182, 3313, 3434, 3546, 3649,
+  3741, 3823, 3895, 3955, 4006, 4045, 4073, 4089, 4095, 4089, 4073, 4045, 4006, 3955, 3895, 3823, 3741, 3649, 3546, 3434, 3313,
+  3182, 3043, 2896, 2740, 2577, 2407, 2230, 2048, 1859, 1666, 1468, 1265, 1060, 851, 641, 428, 214, 0, -214, -428, -641, -851,
+  -1060, -1265, -1468, -1666, -1859, -2047, -2230, -2407, -2577, -2740, -2896, -3043, -3182, -3313, -3434, -3546, -3649, -3741,
+  -3823, -3895, -3955, -4006, -4045, -4073, -4089, -4095, -4089, -4073, -4045, -4006, -3955, -3895, -3823, -3741, -3649, -3546,
+  -3434, -3313, -3182, -3043, -2896, -2740, -2577, -2407, -2230, -2047, -1859, -1666, -1468, -1265, -1060, -851, -641, -428, -214
+};
+
+CAX25TX::CAX25TX() :
+m_twist(-6),
+m_poBuffer(),
+m_poLen(0U),
+m_poPtr(0U),
+m_txDelay(120U),
+m_tablePtr(0U),
+m_nrzi(false)
+{
+}
+
+void CAX25TX::process()
+{
+  if (m_poLen == 0U)
+    return;
+
+  uint16_t space = io.getSpace();
+
+  while (space > AX25_RADIO_SYMBOL_LENGTH) {
+    bool b = READ_BIT1(m_poBuffer, m_poPtr) != 0U;
+    m_poPtr++;
+
+    writeBit(b);
+
+    space -= AX25_RADIO_SYMBOL_LENGTH;
+
+    if (m_poPtr >= m_poLen) {
+      m_poPtr = 0U;
+      m_poLen = 0U;
+      return;
+    }
+  }
+}
+
+uint8_t CAX25TX::writeData(const uint8_t* data, uint16_t length)
+{
+  CAX25Frame frame(data, length);
+  frame.addCRC();
+
+  m_poLen    = 0U;
+  m_poPtr    = 0U;
+  m_nrzi     = false;
+  m_tablePtr = 0U;
+
+  // Add TX delay (already NRZI)
+  for (uint16_t i = 0U; i < m_txDelay; i++, m_poLen++)
+    WRITE_BIT1(m_poBuffer, m_poLen, false);
+
+  // Add the Start Flag
+  for (uint16_t i = 0U; i < 8U; i++, m_poLen++) {
+    bool b1 = READ_BIT1(START_FLAG, i) != 0U;
+    bool b2 = NRZI(b1);
+    WRITE_BIT1(m_poBuffer, m_poLen, b2);
+  }
+
+  uint8_t ones = 0U;
+  for (uint16_t i = 0U; i < (frame.m_length * 8U); i++) {
+    bool b1 = READ_BIT2(frame.m_data, i) != 0U;
+    bool b2 = NRZI(b1);
+    WRITE_BIT1(m_poBuffer, m_poLen, b2);
+    m_poLen++;
+
+    if (b1) {
+      ones++;
+      if (ones == AX25_MAX_ONES) {
+        // Bit stuffing
+        bool b = NRZI(false);
+        WRITE_BIT1(m_poBuffer, m_poLen, b);
+        m_poLen++;
+        ones = 0U;
+      }
+    } else {
+      ones = 0U;
+    }
+  }
+
+  // Add the End Flag
+  for (uint16_t i = 0U; i < 8U; i++, m_poLen++) {
+    bool b1 = READ_BIT1(END_FLAG, i) != 0U;
+    bool b2 = NRZI(b1);
+    WRITE_BIT1(m_poBuffer, m_poLen, b2);
+  }
+
+  return 0U;
+}
+
+void CAX25TX::writeBit(bool b)
+{
+  q15_t in[AX25_RADIO_SYMBOL_LENGTH];
+  for (uint8_t i = 0U; i < AX25_RADIO_SYMBOL_LENGTH; i++) {
+    in[i] = AUDIO_TABLE_DATA[m_tablePtr];
+    if (b)
+      m_tablePtr += 6U;
+    else
+      m_tablePtr += 11U;
+
+    if (m_tablePtr >= AUDIO_TABLE_LEN)
+      m_tablePtr -= AUDIO_TABLE_LEN;
+  }
+
+  q15_t out[AX25_RADIO_SYMBOL_LENGTH];
+  m_twist.process(in, out, AX25_RADIO_SYMBOL_LENGTH);
+
+  io.write(STATE_AX25, out, AX25_RADIO_SYMBOL_LENGTH);
+}
+
+void CAX25TX::setParams(int8_t twist)
+{
+  m_twist.setTwist(twist);
+}
+
+void CAX25TX::setTXDelay(uint8_t delay)
+{
+  m_txDelay = delay * 12U;
+}
+
+uint8_t CAX25TX::getSpace() const
+{
+  return m_poLen == 0U ? 255U : 0U;
+}
+
+bool CAX25TX::NRZI(bool b)
+{
+    bool result = (b == m_nrzi);
+
+    m_nrzi = b;
+
+    return result;
+}
+

AX25TX.h

@@ -0,0 +1,54 @@
+/*
+ *   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(AX25TX_H)
+#define  AX25TX_H
+
+#include "Config.h"
+
+#include "AX25Twist.h"
+
+class CAX25TX {
+public:
+  CAX25TX();
+
+  uint8_t writeData(const uint8_t* data, uint16_t length);
+
+  void process();
+
+  void setParams(int8_t twist);
+
+  void setTXDelay(uint8_t delay);
+
+  uint8_t getSpace() const;
+
+private:
+  CAX25Twist m_twist;
+  uint8_t    m_poBuffer[600U];
+  uint16_t   m_poLen;
+  uint16_t   m_poPtr;
+  uint16_t   m_txDelay;
+  uint16_t   m_tablePtr;
+  bool       m_nrzi;
+
+  void writeBit(bool b);
+  bool NRZI(bool b);
+};
+
+#endif
+

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
+

CWIdTX.cpp

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2009-2017 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2009-2017,2020 by Jonathan Naylor G4KLX
  *   Copyright (C) 2016 by Colin Durbridge G4EML
  *
  *   This program is free software; you can redistribute it and/or modify
@@ -125,7 +125,7 @@ void CCWIdTX::process()
   }
 }
 
-uint8_t CCWIdTX::write(const uint8_t* data, uint8_t length)
+uint8_t CCWIdTX::write(const uint8_t* data, uint16_t length)
 {
   ::memset(m_poBuffer, 0x00U, 1000U * sizeof(uint8_t));
 

CWIdTX.h

@@ -1,6 +1,6 @@
 /*
  *   Copyright (C) 2009-2015 by Jonathan Naylor G4KLX
- *   Copyright (C) 2016 by Colin Durbridge G4EML
+ *   Copyright (C) 2016,2020 by Colin Durbridge G4EML
  *
  *   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
@@ -28,7 +28,7 @@ public:
 
   void process();
 
-  uint8_t write(const uint8_t* data, uint8_t length);
+  uint8_t write(const uint8_t* data, uint16_t length);
 
   void reset();
 

CalDMR.cpp

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2009-2015 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2009-2015,2020 by Jonathan Naylor G4KLX
  *   Copyright (C) 2016 by Colin Durbridge G4EML
  *
  *   This program is free software; you can redistribute it and/or modify
@@ -208,7 +208,7 @@ void CCalDMR::dmrdmo1k()
   }
 }
 
-uint8_t CCalDMR::write(const uint8_t* data, uint8_t length)
+uint8_t CCalDMR::write(const uint8_t* data, uint16_t length)
 {
   if (length != 1U)
     return 4U;

CalDMR.h

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2009-2015 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2009-2015,2020 by Jonathan Naylor G4KLX
  *   Copyright (C) 2016 by Colin Durbridge G4EML
  *
  *   This program is free software; you can redistribute it and/or modify
@@ -41,7 +41,7 @@ public:
   void createData1k(uint8_t n);
   void createDataDMO1k(uint8_t n);
 
-  uint8_t write(const uint8_t* data, uint8_t length);
+  uint8_t write(const uint8_t* data, uint16_t length);
 
 private:
   bool      m_transmit;

CalDStarTX.cpp

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2009-2016 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2009-2016,2020 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
@@ -162,7 +162,7 @@ void CCalDStarTX::process()
   m_count = (m_count + 1U) % (30U * 21U);
 }
 
-uint8_t CCalDStarTX::write(const uint8_t* data, uint8_t length)
+uint8_t CCalDStarTX::write(const uint8_t* data, uint16_t length)
 {
   if (length != 1U)
     return 4U;

CalDStarTX.h

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2015,2016 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2015,2016,2020 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
@@ -26,7 +26,7 @@ class CCalDStarTX {
 public:
   CCalDStarTX();
 
-  uint8_t write(const uint8_t* data, uint8_t length);
+  uint8_t write(const uint8_t* data, uint16_t length);
 
   void process();
 

CalFM.cpp

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2009-2015 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2009-2015,2020 by Jonathan Naylor G4KLX
  *   Copyright (C) 2016 by Colin Durbridge G4EML
  *   Copyright (C) 2020 by Phil Taylor M0VSE
  *
@@ -116,7 +116,7 @@ void CCalFM::process()
 }
 
 
-uint8_t CCalFM::write(const uint8_t* data, uint8_t length)
+uint8_t CCalFM::write(const uint8_t* data, uint16_t length)
 {
   if (length != 1U)
     return 4U;

CalFM.h

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2009-2015 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2009-2015,2020 by Jonathan Naylor G4KLX
  *   Copyright (C) 2016 by Colin Durbridge G4EML
  *   Copyright (C) 2020 by Phil Taylor M0VSE
  *
@@ -35,7 +35,7 @@ public:
   void fm25kcal();
   void fm30kcal();
 
-  uint8_t write(const uint8_t* data, uint8_t length);
+  uint8_t write(const uint8_t* data, uint16_t length);
 
 private:
   uint16_t  m_frequency;

CalNXDN.cpp

@@ -1,5 +1,6 @@
 /*
  *   Copyright (C) 2018 by Andy Uribe CA6JAU
+ *   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
@@ -79,7 +80,7 @@ void CCalNXDN::process()
   }
 }
 
-uint8_t CCalNXDN::write(const uint8_t* data, uint8_t length)
+uint8_t CCalNXDN::write(const uint8_t* data, uint16_t length)
 {
   if (length != 1U)
     return 4U;

CalNXDN.h

@@ -1,5 +1,6 @@
 /*
  *   Copyright (C) 2018 by Andy Uribe CA6JAU
+ *   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
@@ -32,7 +33,7 @@ public:
 
   void process();
 
-  uint8_t write(const uint8_t* data, uint8_t length);
+  uint8_t write(const uint8_t* data, uint16_t length);
 
 private:
   bool      m_transmit;

CalP25.cpp

@@ -1,5 +1,6 @@
 /*
  *   Copyright (C) 2018 by Andy Uribe CA6JAU
+ *   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
@@ -82,7 +83,7 @@ void CCalP25::process()
   }
 }
 
-uint8_t CCalP25::write(const uint8_t* data, uint8_t length)
+uint8_t CCalP25::write(const uint8_t* data, uint16_t length)
 {
   if (length != 1U)
     return 4U;

CalP25.h

@@ -1,5 +1,6 @@
 /*
  *   Copyright (C) 2018 by Andy Uribe CA6JAU
+ *   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
@@ -34,7 +35,7 @@ public:
 
   void process();
 
-  uint8_t write(const uint8_t* data, uint8_t length);
+  uint8_t write(const uint8_t* data, uint16_t length);
 
 private:
   bool      m_transmit;

CalPOCSAG.cpp

@@ -1,5 +1,6 @@
 /*
  *   Copyright (C) 2019 by Florian Wolters DF2ET
+ *   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
@@ -38,7 +39,7 @@ void CCalPOCSAG::process()
   pocsagTX.writeByte(0xAAU);
 }
 
-uint8_t CCalPOCSAG::write(const uint8_t* data, uint8_t length)
+uint8_t CCalPOCSAG::write(const uint8_t* data, uint16_t length)
 {
   if (length != 1U)
     return 4U;

CalPOCSAG.h

@@ -1,5 +1,6 @@
 /*
  *   Copyright (C) 2019 by Florian Wolters DF2ET
+ *   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
@@ -32,7 +33,7 @@ public:
 
   void process();
 
-  uint8_t write(const uint8_t* data, uint8_t length);
+  uint8_t write(const uint8_t* data, uint16_t length);
 
 private:
   POCSAGCAL m_state;

Config.h

@@ -36,7 +36,7 @@
 // #define EXTERNAL_OSC 19200000
 
 // Use pins to output the current mode via LEDs
-// #define MODE_LEDS
+#define MODE_LEDS
 
 // For the original Arduino Due pin layout
 // #define ARDUINO_DUE_PAPA

DMRDMOTX.cpp

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2009-2017 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2009-2017,2020 by Jonathan Naylor G4KLX
  *   Copyright (C) 2016 by Colin Durbridge G4EML
  *   Copyright (C) 2017 by Andy Uribe CA6JAU
  *
@@ -104,7 +104,7 @@ void CDMRDMOTX::process()
   }
 }
 
-uint8_t CDMRDMOTX::writeData(const uint8_t* data, uint8_t length)
+uint8_t CDMRDMOTX::writeData(const uint8_t* data, uint16_t length)
 {
   if (length != (DMR_FRAME_LENGTH_BYTES + 1U))
     return 4U;

DMRDMOTX.h

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2015,2016,2017 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2015,2016,2017,2020 by Jonathan Naylor G4KLX
  *   Copyright (C) 2016 by Colin Durbridge G4EML
  *
  *   This program is free software; you can redistribute it and/or modify
@@ -29,7 +29,7 @@ class CDMRDMOTX {
 public:
   CDMRDMOTX();
 
-  uint8_t writeData(const uint8_t* data, uint8_t length);
+  uint8_t writeData(const uint8_t* data, uint16_t length);
 
   void process();
 

DMRTX.cpp

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2009-2017 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2009-2017,2020 by Jonathan Naylor G4KLX
  *   Copyright (C) 2016 by Colin Durbridge G4EML
  *   Copyright (C) 2017 by Andy Uribe CA6JAU
  *
@@ -144,7 +144,7 @@ void CDMRTX::process()
   }
 }
 
-uint8_t CDMRTX::writeData1(const uint8_t* data, uint8_t length)
+uint8_t CDMRTX::writeData1(const uint8_t* data, uint16_t length)
 {
   if (length != (DMR_FRAME_LENGTH_BYTES + 1U))
     return 4U;
@@ -168,7 +168,7 @@ uint8_t CDMRTX::writeData1(const uint8_t* data, uint8_t length)
   return 0U;
 }
 
-uint8_t CDMRTX::writeData2(const uint8_t* data, uint8_t length)
+uint8_t CDMRTX::writeData2(const uint8_t* data, uint16_t length)
 {
   if (length != (DMR_FRAME_LENGTH_BYTES + 1U))
     return 4U;
@@ -192,7 +192,7 @@ uint8_t CDMRTX::writeData2(const uint8_t* data, uint8_t length)
   return 0U;
 }
 
-uint8_t CDMRTX::writeShortLC(const uint8_t* data, uint8_t length)
+uint8_t CDMRTX::writeShortLC(const uint8_t* data, uint16_t length)
 {
   if (length != 9U)
     return 4U;
@@ -208,7 +208,7 @@ uint8_t CDMRTX::writeShortLC(const uint8_t* data, uint8_t length)
   return 0U;
 }
 
-uint8_t CDMRTX::writeAbort(const uint8_t* data, uint8_t length)
+uint8_t CDMRTX::writeAbort(const uint8_t* data, uint16_t length)
 {
   if (length != 1U)
     return 4U;

DMRTX.h

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2015,2016,2017 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2015,2016,2017,2020 by Jonathan Naylor G4KLX
  *   Copyright (C) 2016 by Colin Durbridge G4EML
  *
  *   This program is free software; you can redistribute it and/or modify
@@ -38,11 +38,11 @@ class CDMRTX {
 public:
   CDMRTX();
 
-  uint8_t writeData1(const uint8_t* data, uint8_t length);
-  uint8_t writeData2(const uint8_t* data, uint8_t length);
+  uint8_t writeData1(const uint8_t* data, uint16_t length);
+  uint8_t writeData2(const uint8_t* data, uint16_t length);
 
-  uint8_t writeShortLC(const uint8_t* data, uint8_t length);
-  uint8_t writeAbort(const uint8_t* data, uint8_t length);
+  uint8_t writeShortLC(const uint8_t* data, uint16_t length);
+  uint8_t writeAbort(const uint8_t* data, uint16_t length);
 
   void setStart(bool start);
   void setCal(bool start);

DStarTX.cpp

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2009-2017 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2009-2017,2020 by Jonathan Naylor G4KLX
  *   Copyright (C) 2017 by Andy Uribe CA6JAU
  *
  *   This program is free software; you can redistribute it and/or modify
@@ -277,7 +277,7 @@ void CDStarTX::process()
   }
 }
 
-uint8_t CDStarTX::writeHeader(const uint8_t* header, uint8_t length)
+uint8_t CDStarTX::writeHeader(const uint8_t* header, uint16_t length)
 {
   if (length != DSTAR_HEADER_LENGTH_BYTES)
     return 4U;
@@ -296,7 +296,7 @@ uint8_t CDStarTX::writeHeader(const uint8_t* header, uint8_t length)
   return 0U;
 }
 
-uint8_t CDStarTX::writeData(const uint8_t* data, uint8_t length)
+uint8_t CDStarTX::writeData(const uint8_t* data, uint16_t length)
 {
   if (length != DSTAR_DATA_LENGTH_BYTES)
     return 4U;

DStarTX.h

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2015,2016,2017 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2015,2016,2017,2020 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
@@ -27,8 +27,8 @@ class CDStarTX {
 public:
   CDStarTX();
 
-  uint8_t writeHeader(const uint8_t* header, uint8_t length);
-  uint8_t writeData(const uint8_t* data, uint8_t length);
+  uint8_t writeHeader(const uint8_t* header, uint16_t length);
+  uint8_t writeData(const uint8_t* data, uint16_t length);
   uint8_t writeEOT();
 
   void process();

Globals.h

@@ -51,6 +51,7 @@ enum MMDVM_STATE {
   STATE_NXDN      = 5,
   STATE_POCSAG    = 6,
   STATE_FM        = 10,
+  STATE_AX25      = 11,
 
   // Dummy states start at 90
   STATE_NXDNCAL1K = 91,
@@ -96,6 +97,8 @@ enum MMDVM_STATE {
 #include "CalPOCSAG.h"
 #include "CalRSSI.h"
 #include "CWIdTX.h"
+#include "AX25RX.h"
+#include "AX25TX.h"
 #include "Debug.h"
 #include "IO.h"
 #include "FM.h"
@@ -124,6 +127,7 @@ extern bool m_p25Enable;
 extern bool m_nxdnEnable;
 extern bool m_pocsagEnable;
 extern bool m_fmEnable;
+extern bool m_ax25Enable;
 
 extern bool m_duplex;
 
@@ -154,7 +158,9 @@ extern CNXDNTX nxdnTX;
 
 extern CPOCSAGTX pocsagTX;
 
-extern CFM fm;
+extern CFM     fm;
+extern CAX25RX ax25RX;
+extern CAX25TX ax25TX;
 
 extern CCalDStarRX calDStarRX;
 extern CCalDStarTX calDStarTX;
@@ -168,3 +174,4 @@ extern CCalRSSI    calRSSI;
 extern CCWIdTX cwIdTX;
 
 #endif
+

IO.cpp

@@ -81,6 +81,7 @@ m_p25TXLevel(128 * 128),
 m_nxdnTXLevel(128 * 128),
 m_pocsagTXLevel(128 * 128),
 m_fmTXLevel(128 * 128),
+m_ax25TXLevel(128 * 128),
 m_rxDCOffset(DC_OFFSET),
 m_txDCOffset(DC_OFFSET),
 m_useCOSAsLockout(false),
@@ -362,6 +363,14 @@ void CIO::process()
         fm.samples(cos, dcSamples, RX_BLOCK_SIZE);
 #else
         fm.samples(cos, samples, RX_BLOCK_SIZE);
+#endif
+      }
+
+      if (m_ax25Enable) {
+#if defined(USE_DCBLOCKER)
+        ax25RX.samples(dcSamples, RX_BLOCK_SIZE);
+#else
+        ax25RX.samples(samples, RX_BLOCK_SIZE);
 #endif
       }
     } else if (m_modemState == STATE_DSTAR) {
@@ -426,8 +435,12 @@ void CIO::process()
       bool cos = getCOSInt();
 #if defined(USE_DCBLOCKER)
       fm.samples(cos, dcSamples, RX_BLOCK_SIZE);
+      if (m_ax25Enable)
+        ax25RX.samples(dcSamples, RX_BLOCK_SIZE);
 #else
       fm.samples(cos, samples, RX_BLOCK_SIZE);
+      if (m_ax25Enable)
+        ax25RX.samples(samples, RX_BLOCK_SIZE);
 #endif
     } else if (m_modemState == STATE_DSTARCAL) {
       q15_t GMSKVals[RX_BLOCK_SIZE];
@@ -477,6 +490,9 @@ void CIO::write(MMDVM_STATE mode, q15_t* samples, uint16_t length, const uint8_t
     case STATE_FM:
       txLevel = m_fmTXLevel;
       break;
+    case STATE_AX25:
+      txLevel = m_ax25TXLevel;
+      break;
     default:
       txLevel = m_cwIdTXLevel;
       break;
@@ -529,7 +545,7 @@ void CIO::setMode()
 #endif
 }
 
-void CIO::setParameters(bool rxInvert, bool txInvert, bool pttInvert, uint8_t rxLevel, uint8_t cwIdTXLevel, uint8_t dstarTXLevel, uint8_t dmrTXLevel, uint8_t ysfTXLevel, uint8_t p25TXLevel, uint8_t nxdnTXLevel, uint8_t pocsagTXLevel, uint8_t fmTXLevel, int16_t txDCOffset, int16_t rxDCOffset, bool useCOSAsLockout)
+void CIO::setParameters(bool rxInvert, bool txInvert, bool pttInvert, uint8_t rxLevel, uint8_t cwIdTXLevel, uint8_t dstarTXLevel, uint8_t dmrTXLevel, uint8_t ysfTXLevel, uint8_t p25TXLevel, uint8_t nxdnTXLevel, uint8_t pocsagTXLevel, uint8_t fmTXLevel, uint8_t ax25TXLevel, int16_t txDCOffset, int16_t rxDCOffset, bool useCOSAsLockout)
 {
   m_pttInvert = pttInvert;
 
@@ -542,6 +558,7 @@ void CIO::setParameters(bool rxInvert, bool txInvert, bool pttInvert, uint8_t rx
   m_nxdnTXLevel   = q15_t(nxdnTXLevel * 128);
   m_pocsagTXLevel = q15_t(pocsagTXLevel * 128);
   m_fmTXLevel     = q15_t(fmTXLevel * 128);
+  m_ax25TXLevel   = q15_t(ax25TXLevel * 128);
 
   m_rxDCOffset   = DC_OFFSET + rxDCOffset;
   m_txDCOffset   = DC_OFFSET + txDCOffset;

IO.h

@@ -42,7 +42,7 @@ public:
   
   void interrupt();
 
-  void setParameters(bool rxInvert, bool txInvert, bool pttInvert, uint8_t rxLevel, uint8_t cwIdTXLevel, uint8_t dstarTXLevel, uint8_t dmrTXLevel, uint8_t ysfTXLevel, uint8_t p25TXLevel, uint8_t nxdnTXLevel, uint8_t pocsagTXLevel, uint8_t fmTXLevel, int16_t txDCOffset, int16_t rxDCOffset, bool useCOSAsLockout);
+  void setParameters(bool rxInvert, bool txInvert, bool pttInvert, uint8_t rxLevel, uint8_t cwIdTXLevel, uint8_t dstarTXLevel, uint8_t dmrTXLevel, uint8_t ysfTXLevel, uint8_t p25TXLevel, uint8_t nxdnTXLevel, uint8_t pocsagTXLevel, uint8_t fmTXLevel, uint8_t ax25TXLevel, int16_t txDCOffset, int16_t rxDCOffset, bool useCOSAsLockout);
 
   void getOverflow(bool& adcOverflow, bool& dacOverflow);
 
@@ -87,6 +87,7 @@ private:
   q15_t                m_nxdnTXLevel;
   q15_t                m_pocsagTXLevel;
   q15_t                m_fmTXLevel;
+  q15_t                m_ax25TXLevel;
 
   uint16_t             m_rxDCOffset;
   uint16_t             m_txDCOffset;

MMDVM.cpp

@@ -33,6 +33,7 @@ bool m_p25Enable    = true;
 bool m_nxdnEnable   = true;
 bool m_pocsagEnable = true;
 bool m_fmEnable     = true;
+bool m_ax25Enable   = true;
 
 bool m_duplex = true;
 
@@ -61,6 +62,8 @@ CNXDNTX    nxdnTX;
 CPOCSAGTX  pocsagTX;
 
 CFM        fm;
+CAX25RX    ax25RX;
+CAX25TX    ax25TX;
 
 CCalDStarRX calDStarRX;
 CCalDStarTX calDStarTX;
@@ -110,6 +113,9 @@ void loop()
   if (m_pocsagEnable && (m_modemState == STATE_POCSAG || pocsagTX.busy()))
     pocsagTX.process();
 
+  if (m_ax25Enable && (m_modemState == STATE_IDLE || m_modemState == STATE_FM))
+    ax25TX.process();
+
   if (m_fmEnable && m_modemState == STATE_FM)
     fm.process();
 

MMDVM.ino

@@ -30,6 +30,7 @@ bool m_p25Enable    = true;
 bool m_nxdnEnable   = true;
 bool m_pocsagEnable = true;
 bool m_fmEnable     = true;
+bool m_ax25Enable   = true;
 
 bool m_duplex = true;
 
@@ -58,6 +59,8 @@ CNXDNTX    nxdnTX;
 CPOCSAGTX  pocsagTX;
 
 CFM        fm;
+CAX25RX    ax25RX;
+CAX25      ax25TX;
 
 CCalDStarRX calDStarRX;
 CCalDStarTX calDStarTX;
@@ -107,6 +110,9 @@ void loop()
   if (m_pocsagEnable && (m_modemState == STATE_POCSAG || pocsagTX.busy()))
     pocsagTX.process();
 
+  if (m_ax25Enable && (m_modemState == STATE_IDLE || m_modemState == STATE_FM))
+    ax25TX.process();
+
   if (m_fmEnable && m_modemState == STATE_FM)
     fm.process();
 

NXDNTX.cpp

@@ -122,7 +122,7 @@ void CNXDNTX::process()
   }
 }
 
-uint8_t CNXDNTX::writeData(const uint8_t* data, uint8_t length)
+uint8_t CNXDNTX::writeData(const uint8_t* data, uint16_t length)
 {
   if (length != (NXDN_FRAME_LENGTH_BYTES + 1U))
     return 4U;

NXDNTX.h

@@ -27,7 +27,7 @@ class CNXDNTX {
 public:
   CNXDNTX();
 
-  uint8_t writeData(const uint8_t* data, uint8_t length);
+  uint8_t writeData(const uint8_t* data, uint16_t length);
 
   void process();
 

P25TX.cpp

@@ -118,7 +118,7 @@ void CP25TX::process()
   }
 }
 
-uint8_t CP25TX::writeData(const uint8_t* data, uint8_t length)
+uint8_t CP25TX::writeData(const uint8_t* data, uint16_t length)
 {
   if (length < (P25_TERM_FRAME_LENGTH_BYTES + 1U))
     return 4U;

P25TX.h

@@ -27,7 +27,7 @@ class CP25TX {
 public:
   CP25TX();
 
-  uint8_t writeData(const uint8_t* data, uint8_t length);
+  uint8_t writeData(const uint8_t* data, uint16_t length);
 
   void process();
 

POCSAGTX.cpp

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2009-2018 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2009-2018,2020 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
@@ -95,7 +95,7 @@ bool CPOCSAGTX::busy()
     return false;
 }
 
-uint8_t CPOCSAGTX::writeData(const uint8_t* data, uint8_t length)
+uint8_t CPOCSAGTX::writeData(const uint8_t* data, uint16_t length)
 {
   if (length != POCSAG_FRAME_LENGTH_BYTES)
     return 4U;

POCSAGTX.h

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2015-2019 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2015-2020 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
@@ -27,7 +27,7 @@ class CPOCSAGTX {
 public:
   CPOCSAGTX();
 
-  uint8_t writeData(const uint8_t* data, uint8_t length);
+  uint8_t writeData(const uint8_t* data, uint16_t length);
 
   void writeByte(uint8_t c);
 

SerialPort.cpp

@@ -65,6 +65,8 @@ const uint8_t MMDVM_NXDN_LOST    = 0x41U;
 
 const uint8_t MMDVM_POCSAG_DATA  = 0x50U;
 
+const uint8_t MMDVM_AX25_DATA    = 0x55U;
+
 const uint8_t MMDVM_FM_PARAMS1   = 0x60U;
 const uint8_t MMDVM_FM_PARAMS2   = 0x61U;
 const uint8_t MMDVM_FM_PARAMS3   = 0x62U;
@@ -103,7 +105,7 @@ const uint8_t MMDVM_DEBUG5       = 0xF5U;
 #define	HW_TYPE	"MMDVM"
 #endif
 
-#define DESCRIPTION "20200714 (D-Star/DMR/System Fusion/P25/NXDN/POCSAG/FM)"
+#define DESCRIPTION "20200714 (D-Star/DMR/System Fusion/P25/NXDN/POCSAG/FM/AX.25)"
 
 #if defined(GITVERSION)
 #define concat(h, a, b, c) h " " a " " b " GitID #" c ""
@@ -176,6 +178,8 @@ void CSerialPort::getStatus()
     reply[3U] |= 0x20U;
   if (m_fmEnable)
     reply[3U] |= 0x40U;
+  if (m_ax25Enable)
+    reply[3U] |= 0x80U;
 
   reply[4U]  = uint8_t(m_modemState);
 
@@ -240,7 +244,12 @@ void CSerialPort::getStatus()
   else
     reply[12U] = 0U;
 
-  writeInt(1U, reply, 13);
+  if (m_ax25Enable)
+    reply[13U] = ax25TX.getSpace();
+  else
+    reply[13U] = 0U;
+
+  writeInt(1U, reply, 14);
 }
 
 void CSerialPort::getVersion()
@@ -262,9 +271,9 @@ void CSerialPort::getVersion()
   writeInt(1U, reply, count);
 }
 
-uint8_t CSerialPort::setConfig(const uint8_t* data, uint8_t length)
+uint8_t CSerialPort::setConfig(const uint8_t* data, uint16_t length)
 {
-  if (length < 21U)
+  if (length < 24U)
     return 4U;
 
   bool rxInvert        = (data[0U] & 0x01U) == 0x01U;
@@ -283,6 +292,7 @@ uint8_t CSerialPort::setConfig(const uint8_t* data, uint8_t length)
   bool nxdnEnable   = (data[1U] & 0x10U) == 0x10U;
   bool pocsagEnable = (data[1U] & 0x20U) == 0x20U;
   bool fmEnable     = (data[1U] & 0x40U) == 0x40U;
+  bool ax25Enable   = (data[1U] & 0x80U) == 0x80U;
 
   uint8_t txDelay = data[2U];
   if (txDelay > 50U)
@@ -336,6 +346,16 @@ uint8_t CSerialPort::setConfig(const uint8_t* data, uint8_t length)
 
   uint8_t nxdnTXHang    = data[20U];
 
+  uint8_t ax25TXLevel   = data[21U];
+
+  int8_t ax25RXTwist    = int8_t(data[22U]) - 128;
+  if (ax25RXTwist < -4 || ax25RXTwist > 10)
+    return 4U;
+
+  int8_t ax25TXTwist    = int8_t(data[23U]) - 128;
+  if (ax25TXTwist < -4 || ax25TXTwist > 10)
+    return 4U;
+
   setMode(modemState);
 
   m_dstarEnable  = dstarEnable;
@@ -345,6 +365,7 @@ uint8_t CSerialPort::setConfig(const uint8_t* data, uint8_t length)
   m_nxdnEnable   = nxdnEnable;
   m_pocsagEnable = pocsagEnable;
   m_fmEnable     = fmEnable;
+  m_ax25Enable   = ax25Enable;
   m_duplex       = !simplex;
 
   dstarTX.setTXDelay(txDelay);
@@ -353,6 +374,7 @@ uint8_t CSerialPort::setConfig(const uint8_t* data, uint8_t length)
   dmrDMOTX.setTXDelay(txDelay);
   nxdnTX.setTXDelay(txDelay);
   pocsagTX.setTXDelay(txDelay);
+  ax25TX.setTXDelay(txDelay);
 
   dmrTX.setColorCode(colorCode);
   dmrRX.setColorCode(colorCode);
@@ -363,15 +385,17 @@ uint8_t CSerialPort::setConfig(const uint8_t* data, uint8_t length)
   ysfTX.setParams(ysfLoDev, ysfTXHang);
   p25TX.setParams(p25TXHang);
   nxdnTX.setParams(nxdnTXHang);
+  ax25RX.setParams(ax25RXTwist);
+  ax25TX.setParams(ax25TXTwist);
 
-  io.setParameters(rxInvert, txInvert, pttInvert, rxLevel, cwIdTXLevel, dstarTXLevel, dmrTXLevel, ysfTXLevel, p25TXLevel, nxdnTXLevel, pocsagTXLevel, fmTXLevel, txDCOffset, rxDCOffset, useCOSAsLockout);
+  io.setParameters(rxInvert, txInvert, pttInvert, rxLevel, cwIdTXLevel, dstarTXLevel, dmrTXLevel, ysfTXLevel, p25TXLevel, nxdnTXLevel, pocsagTXLevel, fmTXLevel, ax25TXLevel, txDCOffset, rxDCOffset, useCOSAsLockout);
 
   io.start();
 
   return 0U;
 }
 
-uint8_t CSerialPort::setFMParams1(const uint8_t* data, uint8_t length)
+uint8_t CSerialPort::setFMParams1(const uint8_t* data, uint16_t length)
 {
   if (length < 8U)
     return 4U;
@@ -396,7 +420,7 @@ uint8_t CSerialPort::setFMParams1(const uint8_t* data, uint8_t length)
   return fm.setCallsign(callsign, speed, frequency, time, holdoff, highLevel, lowLevel, callAtStart, callAtEnd, callAtLatch);
 }
 
-uint8_t CSerialPort::setFMParams2(const uint8_t* data, uint8_t length)
+uint8_t CSerialPort::setFMParams2(const uint8_t* data, uint16_t length)
 {
   if (length < 6U)
     return 4U;
@@ -416,7 +440,7 @@ uint8_t CSerialPort::setFMParams2(const uint8_t* data, uint8_t length)
   return fm.setAck(ack, speed, frequency, minTime, delay, level);
 }
 
-uint8_t CSerialPort::setFMParams3(const uint8_t* data, uint8_t length)
+uint8_t CSerialPort::setFMParams3(const uint8_t* data, uint16_t length)
 {
   if (length < 12U)
     return 4U;
@@ -442,7 +466,7 @@ uint8_t CSerialPort::setFMParams3(const uint8_t* data, uint8_t length)
   return fm.setMisc(timeout, timeoutLevel, ctcssFrequency, ctcssHighThreshold, ctcssLowThreshold, ctcssLevel, kerchunkTime, hangTime, accessMode, cosInvert, rfAudioBoost, maxDev, rxLevel);
 }
 
-uint8_t CSerialPort::setMode(const uint8_t* data, uint8_t length)
+uint8_t CSerialPort::setMode(const uint8_t* data, uint16_t length)
 {
   if (length < 1U)
     return 4U;
@@ -593,15 +617,25 @@ void CSerialPort::process()
         m_buffer[0U] = c;
         m_ptr = 1U;
         m_len = 0U;
-      }
-      else {
+      } else {
         m_ptr = 0U;
         m_len = 0U;
       }
     } else if (m_ptr == 1U) {
-      // Handle the frame length
+      // Handle the frame length, 1/2
       m_len = m_buffer[m_ptr] = c;
       m_ptr = 2U;
+    } else if (m_ptr == 2U) {
+      // Handle the frame length, 2/2
+      m_buffer[m_ptr] = c;
+      m_ptr = 3U;
+
+      if (m_len == 0U)
+        m_len = c + 255U;
+
+      // The full packet has been received, process it
+      if (m_ptr == m_len)
+        processMessage(m_buffer + 3U, m_len - 3U);
     } else {
       // Any other bytes are added to the buffer
       m_buffer[m_ptr] = c;
@@ -609,304 +643,10 @@ void CSerialPort::process()
 
       // The full packet has been received, process it
       if (m_ptr == m_len) {
-        uint8_t err = 2U;
-
-        switch (m_buffer[2U]) {
-          case MMDVM_GET_STATUS:
-            getStatus();
-            break;
-
-          case MMDVM_GET_VERSION:
-            getVersion();
-            break;
-
-          case MMDVM_SET_CONFIG:
-            err = setConfig(m_buffer + 3U, m_len - 3U);
-            if (err == 0U)
-              sendACK();
-            else
-              sendNAK(err);
-            break;
-
-          case MMDVM_SET_MODE:
-            err = setMode(m_buffer + 3U, m_len - 3U);
-            if (err == 0U)
-              sendACK();
-            else
-              sendNAK(err);
-            break;
-
-          case MMDVM_SET_FREQ:
-            sendACK();
-            break;
-
-          case MMDVM_FM_PARAMS1:
-            err = setFMParams1(m_buffer + 3U, m_len - 3U);
-            if (err == 0U) {
-              sendACK();
-            } else {
-              DEBUG2("Received invalid FM params 1", err);
-              sendNAK(err);
-            }
-            break;
-
-          case MMDVM_FM_PARAMS2:
-            err = setFMParams2(m_buffer + 3U, m_len - 3U);
-            if (err == 0U) {
-              sendACK();
-            } else {
-              DEBUG2("Received invalid FM params 2", err);
-              sendNAK(err);
-            }
-            break;
-
-          case MMDVM_FM_PARAMS3:
-            err = setFMParams3(m_buffer + 3U, m_len - 3U);
-            if (err == 0U) {
-              sendACK();
-            } else {
-              DEBUG2("Received invalid FM params 3", err);
-              sendNAK(err);
-            }
-            break;
-
-          case MMDVM_CAL_DATA:
-            if (m_modemState == STATE_DSTARCAL)
-              err = calDStarTX.write(m_buffer + 3U, m_len - 3U);
-            if (m_modemState == STATE_DMRCAL || m_modemState == STATE_LFCAL || m_modemState == STATE_DMRCAL1K || m_modemState == STATE_DMRDMO1K)
-              err = calDMR.write(m_buffer + 3U, m_len - 3U);
-            if (m_modemState == STATE_FMCAL10K || m_modemState == STATE_FMCAL12K || m_modemState == STATE_FMCAL15K || m_modemState == STATE_FMCAL20K || m_modemState == STATE_FMCAL25K || m_modemState == STATE_FMCAL30K)
-              err = calFM.write(m_buffer + 3U, m_len - 3U);
-            if (m_modemState == STATE_P25CAL1K)
-              err = calP25.write(m_buffer + 3U, m_len - 3U);
-            if (m_modemState == STATE_NXDNCAL1K)
-              err = calNXDN.write(m_buffer + 3U, m_len - 3U);
-            if (m_modemState == STATE_POCSAGCAL)
-              err = calPOCSAG.write(m_buffer + 3U, m_len - 3U);
-            if (err == 0U) {
-              sendACK();
-            } else {
-              DEBUG2("Received invalid calibration data", err);
-              sendNAK(err);
-            }
-            break;
-
-          case MMDVM_SEND_CWID:
-            err = 5U;
-            if (m_modemState == STATE_IDLE)
-              err = cwIdTX.write(m_buffer + 3U, m_len - 3U);
-            if (err != 0U) {
-              DEBUG2("Invalid CW Id data", err);
-              sendNAK(err);
-            }
-            break;
-
-          case MMDVM_DSTAR_HEADER:
-            if (m_dstarEnable) {
-              if (m_modemState == STATE_IDLE || m_modemState == STATE_DSTAR)
-                err = dstarTX.writeHeader(m_buffer + 3U, m_len - 3U);
-            }
-            if (err == 0U) {
-              if (m_modemState == STATE_IDLE)
-                setMode(STATE_DSTAR);
-            } else {
-              DEBUG2("Received invalid D-Star header", err);
-              sendNAK(err);
-            }
-            break;
-
-          case MMDVM_DSTAR_DATA:
-            if (m_dstarEnable) {
-              if (m_modemState == STATE_IDLE || m_modemState == STATE_DSTAR)
-                err = dstarTX.writeData(m_buffer + 3U, m_len - 3U);
-            }
-            if (err == 0U) {
-              if (m_modemState == STATE_IDLE)
-                setMode(STATE_DSTAR);
-            } else {
-              DEBUG2("Received invalid D-Star data", err);
-              sendNAK(err);
-            }
-            break;
-
-          case MMDVM_DSTAR_EOT:
-            if (m_dstarEnable) {
-              if (m_modemState == STATE_IDLE || m_modemState == STATE_DSTAR)
-                err = dstarTX.writeEOT();
-            }
-            if (err == 0U) {
-              if (m_modemState == STATE_IDLE)
-                setMode(STATE_DSTAR);
-            } else {
-              DEBUG2("Received invalid D-Star EOT", err);
-              sendNAK(err);
-            }
-            break;
-
-          case MMDVM_DMR_DATA1:
-            if (m_dmrEnable) {
-              if (m_modemState == STATE_IDLE || m_modemState == STATE_DMR) {
-                if (m_duplex)
-                  err = dmrTX.writeData1(m_buffer + 3U, m_len - 3U);
-              }
-            }
-            if (err == 0U) {
-              if (m_modemState == STATE_IDLE)
-                setMode(STATE_DMR);
-            } else {
-              DEBUG2("Received invalid DMR data", err);
-              sendNAK(err);
-            }
-            break;
-
-          case MMDVM_DMR_DATA2:
-            if (m_dmrEnable) {
-              if (m_modemState == STATE_IDLE || m_modemState == STATE_DMR) {
-                if (m_duplex)
-                  err = dmrTX.writeData2(m_buffer + 3U, m_len - 3U);
-                else
-                  err = dmrDMOTX.writeData(m_buffer + 3U, m_len - 3U);
-              }
-            }
-            if (err == 0U) {
-              if (m_modemState == STATE_IDLE)
-                setMode(STATE_DMR);
-            } else {
-              DEBUG2("Received invalid DMR data", err);
-              sendNAK(err);
-            }
-            break;
-
-          case MMDVM_DMR_START:
-            if (m_dmrEnable) {
-              err = 4U;
-              if (m_len == 4U) {
-                if (m_buffer[3U] == 0x01U && m_modemState == STATE_DMR) {
-                  if (!m_tx)
-                    dmrTX.setStart(true);
-                  err = 0U;
-                } else if (m_buffer[3U] == 0x00U && m_modemState == STATE_DMR) {
-                  if (m_tx)
-                    dmrTX.setStart(false);
-                  err = 0U;
-                }
-              }
-            }
-            if (err != 0U) {
-              DEBUG2("Received invalid DMR start", err);
-              sendNAK(err);
-            }
-            break;
-
-          case MMDVM_DMR_SHORTLC:
-            if (m_dmrEnable)
-              err = dmrTX.writeShortLC(m_buffer + 3U, m_len - 3U);
-            if (err != 0U) {
-              DEBUG2("Received invalid DMR Short LC", err);
-              sendNAK(err);
-            }
-            break;
-
-          case MMDVM_DMR_ABORT:
-            if (m_dmrEnable)
-              err = dmrTX.writeAbort(m_buffer + 3U, m_len - 3U);
-            if (err != 0U) {
-              DEBUG2("Received invalid DMR Abort", err);
-              sendNAK(err);
-            }
-            break;
-
-          case MMDVM_YSF_DATA:
-            if (m_ysfEnable) {
-              if (m_modemState == STATE_IDLE || m_modemState == STATE_YSF)
-                err = ysfTX.writeData(m_buffer + 3U, m_len - 3U);
-            }
-            if (err == 0U) {
-              if (m_modemState == STATE_IDLE)
-                setMode(STATE_YSF);
-            } else {
-              DEBUG2("Received invalid System Fusion data", err);
-              sendNAK(err);
-            }
-            break;
-
-          case MMDVM_P25_HDR:
-            if (m_p25Enable) {
-              if (m_modemState == STATE_IDLE || m_modemState == STATE_P25)
-                err = p25TX.writeData(m_buffer + 3U, m_len - 3U);
-            }
-            if (err == 0U) {
-              if (m_modemState == STATE_IDLE)
-                setMode(STATE_P25);
-            } else {
-              DEBUG2("Received invalid P25 header", err);
-              sendNAK(err);
-            }
-            break;
-
-          case MMDVM_P25_LDU:
-            if (m_p25Enable) {
-              if (m_modemState == STATE_IDLE || m_modemState == STATE_P25)
-                err = p25TX.writeData(m_buffer + 3U, m_len - 3U);
-            }
-            if (err == 0U) {
-              if (m_modemState == STATE_IDLE)
-                setMode(STATE_P25);
-            } else {
-              DEBUG2("Received invalid P25 LDU", err);
-              sendNAK(err);
-            }
-            break;
-
-          case MMDVM_NXDN_DATA:
-            if (m_nxdnEnable) {
-              if (m_modemState == STATE_IDLE || m_modemState == STATE_NXDN)
-                err = nxdnTX.writeData(m_buffer + 3U, m_len - 3U);
-            }
-            if (err == 0U) {
-              if (m_modemState == STATE_IDLE)
-                setMode(STATE_NXDN);
-            } else {
-              DEBUG2("Received invalid NXDN data", err);
-              sendNAK(err);
-            }
-            break;
-
-          case MMDVM_POCSAG_DATA:
-            if (m_pocsagEnable) {
-              if (m_modemState == STATE_IDLE || m_modemState == STATE_POCSAG)
-                err = pocsagTX.writeData(m_buffer + 3U, m_len - 3U);
-            }
-            if (err == 0U) {
-              if (m_modemState == STATE_IDLE)
-                setMode(STATE_POCSAG);
-            } else {
-              DEBUG2("Received invalid POCSAG data", err);
-              sendNAK(err);
-            }
-            break;
-
-          case MMDVM_TRANSPARENT:
-          case MMDVM_QSO_INFO:
-            // Do nothing on the MMDVM.
-            break;
-
-#if defined(SERIAL_REPEATER)
-          case MMDVM_SERIAL: {
-            for (uint8_t i = 3U; i < m_len; i++)
-              m_repeat.put(m_buffer[i]);
-            }
-            break;
-#endif
-
-          default:
-            // Handle this, send a NAK back
-            sendNAK(1U);
-            break;
-        }
-
-        m_ptr = 0U;
-        m_len = 0U;
+        if (m_len > 255U)
+          processMessage(m_buffer + 4U, m_len - 4U);
+        else
+          processMessage(m_buffer + 3U, m_len - 3U);
       }
     }
   }
@@ -936,6 +676,319 @@ void CSerialPort::process()
 #endif
 }
 
+void CSerialPort::processMessage(const uint8_t* buffer, uint16_t length)
+{
+  uint8_t err = 2U;
+
+  switch (m_buffer[2U]) {
+    case MMDVM_GET_STATUS:
+      getStatus();
+      break;
+
+    case MMDVM_GET_VERSION:
+      getVersion();
+      break;
+
+    case MMDVM_SET_CONFIG:
+      err = setConfig(buffer, length);
+      if (err == 0U)
+        sendACK();
+      else
+        sendNAK(err);
+      break;
+
+    case MMDVM_SET_MODE:
+      err = setMode(buffer, length);
+      if (err == 0U)
+        sendACK();
+      else
+        sendNAK(err);
+      break;
+
+    case MMDVM_SET_FREQ:
+      sendACK();
+      break;
+
+    case MMDVM_FM_PARAMS1:
+      err = setFMParams1(buffer, length);
+      if (err == 0U) {
+        sendACK();
+      } else {
+        DEBUG2("Received invalid FM params 1", err);
+        sendNAK(err);
+      }
+      break;
+
+    case MMDVM_FM_PARAMS2:
+      err = setFMParams2(buffer, length);
+      if (err == 0U) {
+        sendACK();
+      } else {
+        DEBUG2("Received invalid FM params 2", err);
+        sendNAK(err);
+      }
+      break;
+
+    case MMDVM_FM_PARAMS3:
+      err = setFMParams3(buffer, length);
+      if (err == 0U) {
+        sendACK();
+      } else {
+        DEBUG2("Received invalid FM params 3", err);
+        sendNAK(err);
+      }
+      break;
+
+    case MMDVM_CAL_DATA:
+      if (m_modemState == STATE_DSTARCAL)
+        err = calDStarTX.write(buffer, length);
+      if (m_modemState == STATE_DMRCAL || m_modemState == STATE_LFCAL || m_modemState == STATE_DMRCAL1K || m_modemState == STATE_DMRDMO1K)
+        err = calDMR.write(buffer, length);
+      if (m_modemState == STATE_FMCAL10K || m_modemState == STATE_FMCAL12K || m_modemState == STATE_FMCAL15K || m_modemState == STATE_FMCAL20K || m_modemState == STATE_FMCAL25K || m_modemState == STATE_FMCAL30K)
+        err = calFM.write(buffer, length);
+      if (m_modemState == STATE_P25CAL1K)
+        err = calP25.write(buffer, length);
+      if (m_modemState == STATE_NXDNCAL1K)
+        err = calNXDN.write(buffer, length);
+      if (m_modemState == STATE_POCSAGCAL)
+        err = calPOCSAG.write(buffer, length);
+      if (err == 0U) {
+        sendACK();
+      } else {
+        DEBUG2("Received invalid calibration data", err);
+        sendNAK(err);
+      }
+      break;
+
+    case MMDVM_SEND_CWID:
+      err = 5U;
+      if (m_modemState == STATE_IDLE)
+        err = cwIdTX.write(buffer, length);
+      if (err != 0U) {
+        DEBUG2("Invalid CW Id data", err);
+        sendNAK(err);
+      }
+      break;
+
+    case MMDVM_DSTAR_HEADER:
+      if (m_dstarEnable) {
+        if (m_modemState == STATE_IDLE || m_modemState == STATE_DSTAR)
+          err = dstarTX.writeHeader(buffer, length);
+      }
+      if (err == 0U) {
+        if (m_modemState == STATE_IDLE)
+          setMode(STATE_DSTAR);
+      } else {
+        DEBUG2("Received invalid D-Star header", err);
+        sendNAK(err);
+      }
+      break;
+
+    case MMDVM_DSTAR_DATA:
+      if (m_dstarEnable) {
+        if (m_modemState == STATE_IDLE || m_modemState == STATE_DSTAR)
+          err = dstarTX.writeData(buffer, length);
+      }
+      if (err == 0U) {
+        if (m_modemState == STATE_IDLE)
+          setMode(STATE_DSTAR);
+      } else {
+        DEBUG2("Received invalid D-Star data", err);
+        sendNAK(err);
+      }
+      break;
+
+    case MMDVM_DSTAR_EOT:
+      if (m_dstarEnable) {
+        if (m_modemState == STATE_IDLE || m_modemState == STATE_DSTAR)
+          err = dstarTX.writeEOT();
+      }
+      if (err == 0U) {
+        if (m_modemState == STATE_IDLE)
+          setMode(STATE_DSTAR);
+      } else {
+        DEBUG2("Received invalid D-Star EOT", err);
+        sendNAK(err);
+      }
+      break;
+
+    case MMDVM_DMR_DATA1:
+      if (m_dmrEnable) {
+        if (m_modemState == STATE_IDLE || m_modemState == STATE_DMR) {
+          if (m_duplex)
+            err = dmrTX.writeData1(buffer, length);
+        }
+      }
+      if (err == 0U) {
+        if (m_modemState == STATE_IDLE)
+          setMode(STATE_DMR);
+      } else {
+        DEBUG2("Received invalid DMR data", err);
+        sendNAK(err);
+      }
+      break;
+
+    case MMDVM_DMR_DATA2:
+      if (m_dmrEnable) {
+        if (m_modemState == STATE_IDLE || m_modemState == STATE_DMR) {
+          if (m_duplex)
+            err = dmrTX.writeData2(buffer, length);
+          else
+            err = dmrDMOTX.writeData(buffer, length);
+        }
+      }
+      if (err == 0U) {
+        if (m_modemState == STATE_IDLE)
+          setMode(STATE_DMR);
+      } else {
+        DEBUG2("Received invalid DMR data", err);
+        sendNAK(err);
+      }
+      break;
+
+    case MMDVM_DMR_START:
+      if (m_dmrEnable) {
+        err = 4U;
+        if (m_len == 4U) {
+          if (m_buffer[3U] == 0x01U && m_modemState == STATE_DMR) {
+            if (!m_tx)
+              dmrTX.setStart(true);
+            err = 0U;
+          } else if (m_buffer[3U] == 0x00U && m_modemState == STATE_DMR) {
+            if (m_tx)
+              dmrTX.setStart(false);
+            err = 0U;
+          }
+        }
+      }
+      if (err != 0U) {
+        DEBUG2("Received invalid DMR start", err);
+        sendNAK(err);
+      }
+      break;
+
+    case MMDVM_DMR_SHORTLC:
+      if (m_dmrEnable)
+        err = dmrTX.writeShortLC(buffer, length);
+      if (err != 0U) {
+        DEBUG2("Received invalid DMR Short LC", err);
+        sendNAK(err);
+      }
+      break;
+
+    case MMDVM_DMR_ABORT:
+      if (m_dmrEnable)
+        err = dmrTX.writeAbort(buffer, length);
+      if (err != 0U) {
+        DEBUG2("Received invalid DMR Abort", err);
+        sendNAK(err);
+      }
+      break;
+
+    case MMDVM_YSF_DATA:
+      if (m_ysfEnable) {
+        if (m_modemState == STATE_IDLE || m_modemState == STATE_YSF)
+          err = ysfTX.writeData(buffer, length);
+      }
+      if (err == 0U) {
+        if (m_modemState == STATE_IDLE)
+          setMode(STATE_YSF);
+      } else {
+        DEBUG2("Received invalid System Fusion data", err);
+        sendNAK(err);
+      }
+      break;
+
+    case MMDVM_P25_HDR:
+      if (m_p25Enable) {
+        if (m_modemState == STATE_IDLE || m_modemState == STATE_P25)
+          err = p25TX.writeData(buffer, length);
+      }
+      if (err == 0U) {
+        if (m_modemState == STATE_IDLE)
+          setMode(STATE_P25);
+      } else {
+        DEBUG2("Received invalid P25 header", err);
+        sendNAK(err);
+      }
+      break;
+
+    case MMDVM_P25_LDU:
+      if (m_p25Enable) {
+        if (m_modemState == STATE_IDLE || m_modemState == STATE_P25)
+          err = p25TX.writeData(buffer, length);
+      }
+      if (err == 0U) {
+        if (m_modemState == STATE_IDLE)
+          setMode(STATE_P25);
+      } else {
+        DEBUG2("Received invalid P25 LDU", err);
+        sendNAK(err);
+      }
+      break;
+
+    case MMDVM_NXDN_DATA:
+      if (m_nxdnEnable) {
+        if (m_modemState == STATE_IDLE || m_modemState == STATE_NXDN)
+          err = nxdnTX.writeData(buffer, length);
+      }
+      if (err == 0U) {
+        if (m_modemState == STATE_IDLE)
+          setMode(STATE_NXDN);
+      } else {
+        DEBUG2("Received invalid NXDN data", err);
+        sendNAK(err);
+      }
+      break;
+
+    case MMDVM_POCSAG_DATA:
+      if (m_pocsagEnable) {
+        if (m_modemState == STATE_IDLE || m_modemState == STATE_POCSAG)
+          err = pocsagTX.writeData(buffer, length);
+      }
+      if (err == 0U) {
+        if (m_modemState == STATE_IDLE)
+          setMode(STATE_POCSAG);
+      } else {
+        DEBUG2("Received invalid POCSAG data", err);
+        sendNAK(err);
+      }
+      break;
+
+    case MMDVM_AX25_DATA:
+      if (m_ax25Enable) {
+        if (m_modemState == STATE_IDLE || m_modemState == STATE_FM)
+          err = ax25TX.writeData(buffer, length);
+      }
+      if (err != 0U) {
+        DEBUG2("Received invalid AX.25 data", err);
+        sendNAK(err);
+      }
+      break;
+
+    case MMDVM_TRANSPARENT:
+    case MMDVM_QSO_INFO:
+      // Do nothing on the MMDVM.
+      break;
+
+#if defined(SERIAL_REPEATER)
+    case MMDVM_SERIAL: {
+      for (uint8_t i = 3U; i < m_len; i++)
+        m_repeat.put(m_buffer[i]);
+      }
+      break;
+#endif
+
+    default:
+      // Handle this, send a NAK back
+      sendNAK(1U);
+      break;
+  }
+
+  m_ptr = 0U;
+  m_len = 0U;
+}
+
 void CSerialPort::writeDStarHeader(const uint8_t* header, uint8_t length)
 {
   if (m_modemState != STATE_DSTAR && m_modemState != STATE_IDLE)
@@ -1198,6 +1251,38 @@ void CSerialPort::writeNXDNLost()
   writeInt(1U, reply, 3);
 }
 
+void CSerialPort::writeAX25Data(const uint8_t* data, uint16_t length)
+{
+  if (m_modemState != STATE_FM && m_modemState != STATE_IDLE)
+    return;
+
+  if (!m_ax25Enable)
+    return;
+
+  uint8_t reply[512U];
+
+  reply[0U] = MMDVM_FRAME_START;
+
+  if (length > 252U) {
+    reply[1U] = 0U;
+    reply[2U] = (length + 4U) - 255U;
+    reply[3U] = MMDVM_AX25_DATA;
+
+    for (uint8_t i = 0U; i < length; i++)
+      reply[i + 4U] = data[i];
+
+    writeInt(1U, reply, length + 4U);
+  } else {
+    reply[1U] = length + 3U;
+    reply[2U] = MMDVM_AX25_DATA;
+
+    for (uint8_t i = 0U; i < length; i++)
+      reply[i + 3U] = data[i];
+
+    writeInt(1U, reply, length + 3U);
+  }
+}
+
 void CSerialPort::writeCalData(const uint8_t* data, uint8_t length)
 {
   if (m_modemState != STATE_DSTARCAL)

SerialPort.h

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2015,2016,2017,2018 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2015,2016,2017,2018,2020 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
@@ -50,6 +50,8 @@ public:
   void writeNXDNData(const uint8_t* data, uint8_t length);
   void writeNXDNLost();
 
+  void writeAX25Data(const uint8_t* data, uint16_t length);
+
   void writeCalData(const uint8_t* data, uint8_t length);
   void writeRSSIData(const uint8_t* data, uint8_t length);
 
@@ -60,9 +62,9 @@ public:
   void writeDebug(const char* text, int16_t n1, int16_t n2, int16_t n3, int16_t n4);
 
 private:
-  uint8_t   m_buffer[256U];
-  uint8_t   m_ptr;
-  uint8_t   m_len;
+  uint8_t   m_buffer[512U];
+  uint16_t  m_ptr;
+  uint16_t  m_len;
   bool      m_debug;
   CSerialRB m_repeat;
 
@@ -70,12 +72,13 @@ private:
   void    sendNAK(uint8_t err);
   void    getStatus();
   void    getVersion();
-  uint8_t setConfig(const uint8_t* data, uint8_t length);
-  uint8_t setMode(const uint8_t* data, uint8_t length);
+  uint8_t setConfig(const uint8_t* data, uint16_t length);
+  uint8_t setMode(const uint8_t* data, uint16_t length);
   void    setMode(MMDVM_STATE modemState);
-  uint8_t setFMParams1(const uint8_t* data, uint8_t length);
-  uint8_t setFMParams2(const uint8_t* data, uint8_t length);
-  uint8_t setFMParams3(const uint8_t* data, uint8_t length);
+  uint8_t setFMParams1(const uint8_t* data, uint16_t length);
+  uint8_t setFMParams2(const uint8_t* data, uint16_t length);
+  uint8_t setFMParams3(const uint8_t* data, uint16_t length);
+  void    processMessage(const uint8_t* data, uint16_t length);
 
   // Hardware versions
   void    beginInt(uint8_t n, int speed);

YSFTX.cpp

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2009-2018 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2009-2018,2020 by Jonathan Naylor G4KLX
  *   Copyright (C) 2017 by Andy Uribe CA6JAU
  *
  *   This program is free software; you can redistribute it and/or modify
@@ -116,7 +116,7 @@ void CYSFTX::process()
   }
 }
 
-uint8_t CYSFTX::writeData(const uint8_t* data, uint8_t length)
+uint8_t CYSFTX::writeData(const uint8_t* data, uint16_t length)
 {
   if (length != (YSF_FRAME_LENGTH_BYTES + 1U))
     return 4U;

YSFTX.h

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2015,2016,2017 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2015,2016,2017,2020 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
@@ -27,7 +27,7 @@ class CYSFTX {
 public:
   CYSFTX();
 
-  uint8_t writeData(const uint8_t* data, uint8_t length);
+  uint8_t writeData(const uint8_t* data, uint16_t length);
 
   void process();