diff --git a/AX25RX.h b/AX25RX.h
index 6ab6d1c..3416b81 100644
--- a/AX25RX.h
+++ b/AX25RX.h
@@ -29,6 +29,8 @@ public:
 
   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
diff --git a/AX25TX.h b/AX25TX.h
new file mode 100644
index 0000000..ffe31be
--- /dev/null
+++ b/AX25TX.h
@@ -0,0 +1,42 @@
+/*
+ *   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"
+
+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:
+};
+
+#endif
+
diff --git a/Globals.h b/Globals.h
index 4d25617..045f628 100644
--- a/Globals.h
+++ b/Globals.h
@@ -98,6 +98,7 @@ enum MMDVM_STATE {
 #include "CalRSSI.h"
 #include "CWIdTX.h"
 #include "AX25RX.h"
+#include "AX25TX.h"
 #include "Debug.h"
 #include "IO.h"
 #include "FM.h"
@@ -159,6 +160,7 @@ extern CPOCSAGTX pocsagTX;
 
 extern CFM     fm;
 extern CAX25RX ax25RX;
+extern CAX25TX ax25TX;
 
 extern CCalDStarRX calDStarRX;
 extern CCalDStarTX calDStarTX;
diff --git a/IO.cpp b/IO.cpp
index 6962f08..27e54b0 100644
--- a/IO.cpp
+++ b/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_ledCount(0U),
@@ -489,6 +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;
@@ -541,7 +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)
+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)
 {
   m_pttInvert = pttInvert;
 
@@ -554,6 +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;
diff --git a/IO.h b/IO.h
index 07ed700..d32be95 100644
--- a/IO.h
+++ b/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);
+  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);
 
   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;
diff --git a/MMDVM.cpp b/MMDVM.cpp
index 5b5bc4b..e80cacf 100644
--- a/MMDVM.cpp
+++ b/MMDVM.cpp
@@ -63,6 +63,7 @@ CPOCSAGTX  pocsagTX;
 
 CFM        fm;
 CAX25RX    ax25RX;
+CAX25TX    ax25TX;
 
 CCalDStarRX calDStarRX;
 CCalDStarTX calDStarTX;
@@ -112,6 +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();
 
diff --git a/MMDVM.ino b/MMDVM.ino
index f1073dd..5785e15 100644
--- a/MMDVM.ino
+++ b/MMDVM.ino
@@ -60,6 +60,7 @@ CPOCSAGTX  pocsagTX;
 
 CFM        fm;
 CAX25RX    ax25RX;
+CAX25      ax25TX;
 
 CCalDStarRX calDStarRX;
 CCalDStarTX calDStarTX;
@@ -109,6 +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();
 
diff --git a/SerialPort.cpp b/SerialPort.cpp
index 8918dff..e8c09b1 100644
--- a/SerialPort.cpp
+++ b/SerialPort.cpp
@@ -105,7 +105,7 @@ const uint8_t MMDVM_DEBUG5       = 0xF5U;
 #define	HW_TYPE	"MMDVM"
 #endif
 
-#define DESCRIPTION "20200617 (D-Star/DMR/System Fusion/P25/NXDN/POCSAG/FM/AX.25)"
+#define DESCRIPTION "20200621 (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 ""
@@ -244,7 +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()
@@ -268,7 +273,7 @@ void CSerialPort::getVersion()
 
 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;
@@ -340,6 +345,16 @@ uint8_t CSerialPort::setConfig(const uint8_t* data, uint16_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;
@@ -358,6 +373,7 @@ uint8_t CSerialPort::setConfig(const uint8_t* data, uint16_t length)
   dmrDMOTX.setTXDelay(txDelay);
   nxdnTX.setTXDelay(txDelay);
   pocsagTX.setTXDelay(txDelay);
+  ax25TX.setTXDelay(txDelay);
 
   dmrTX.setColorCode(colorCode);
   dmrRX.setColorCode(colorCode);
@@ -368,8 +384,10 @@ uint8_t CSerialPort::setConfig(const uint8_t* data, uint16_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);
+  io.setParameters(rxInvert, txInvert, pttInvert, rxLevel, cwIdTXLevel, dstarTXLevel, dmrTXLevel, ysfTXLevel, p25TXLevel, nxdnTXLevel, pocsagTXLevel, fmTXLevel, ax25TXLevel, txDCOffset, rxDCOffset);
 
   io.start();
 
@@ -936,6 +954,17 @@ void CSerialPort::processMessage(const uint8_t* buffer, uint16_t length)
       }
       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.