diff --git a/meson.build b/meson.build
index 89de4f94..780daf06 100644
--- a/meson.build
+++ b/meson.build
@@ -33,11 +33,14 @@ openrtx_src = ['openrtx/src/state.c',
'openrtx/src/rtx/OpMode_FM.cpp',
'openrtx/src/gps.c',
'openrtx/src/dsp.cpp',
- 'openrtx/src/memory_profiling.cpp']
+ 'openrtx/src/memory_profiling.cpp',
+ 'openrtx/src/protocols/M17/M17Callsign.cpp',
+ 'openrtx/src/protocols/M17/M17LinkSetupFrame.cpp']
openrtx_inc = ['openrtx/include',
'openrtx/include/calibration',
'openrtx/include/rtx',
+ 'openrtx/include/protocols',
'platform/drivers/ADC',
'platform/drivers/NVM',
'platform/drivers/GPS',
diff --git a/openrtx/include/protocols/M17/M17Callsign.h b/openrtx/include/protocols/M17/M17Callsign.h
new file mode 100644
index 00000000..411fcaf1
--- /dev/null
+++ b/openrtx/include/protocols/M17/M17Callsign.h
@@ -0,0 +1,55 @@
+/***************************************************************************
+ * Copyright (C) 2021 by Federico Amedeo Izzo IU2NUO, *
+ * Niccolò Izzo IU2KIN *
+ * Frederik Saraci IU2NRO *
+ * Silvano Seva IU2KWO *
+ * *
+ * 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 3 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, see *
+ ***************************************************************************/
+
+#ifndef M17CALLSIGN_H
+#define M17CALLSIGN_H
+
+#ifndef __cplusplus
+#error This header is C++ only!
+#endif
+
+#include
+#include "M17Datatypes.h"
+
+/**
+ * Encode a callsign in base-40 format, starting with the right-most character.
+ * The final value is written out in "big-endian" form, with the most-significant
+ * value first, leading to 0-padding of callsigns shorter than nine characters.
+ *
+ * \param callsign the callsign to encode.
+ * \param encodedCall call_t data structure where to put the encoded data.
+ * \param strict a flag (disabled by default) which indicates whether invalid
+ * characters are allowed and assigned a value of 0 or not allowed, making the
+ * function return an error.
+ * @return true if the callsign was successfully encoded, false on error.
+ */
+bool encode_callsign(const std::string& callsign, call_t& encodedCall,
+ bool strict = false);
+
+/**
+ * Decode a base-40 encoded callsign to its text representation. This decodes
+ * a 6-byte big-endian value into a string of up to 9 characters.
+ *
+ * \param encodedCall base-40 encoded callsign.
+ * \return a string containing the decoded text.
+ */
+std::string decode_callsign(const call_t& encodedCall);
+
+#endif /* M17CALLSIGN_H */
diff --git a/openrtx/include/protocols/M17/M17Datatypes.h b/openrtx/include/protocols/M17/M17Datatypes.h
new file mode 100644
index 00000000..a925e8b3
--- /dev/null
+++ b/openrtx/include/protocols/M17/M17Datatypes.h
@@ -0,0 +1,78 @@
+/***************************************************************************
+ * Copyright (C) 2021 by Federico Amedeo Izzo IU2NUO, *
+ * Niccolò Izzo IU2KIN *
+ * Frederik Saraci IU2NRO *
+ * Silvano Seva IU2KWO *
+ * *
+ * 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 3 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, see *
+ ***************************************************************************/
+
+#ifndef M17DATATYPES_H
+#define M17DATATYPES_H
+
+#include
+#include
+
+#ifndef __cplusplus
+#error This header is C++ only!
+#endif
+
+
+using call_t = std::array< uint8_t, 6 >; // Data type for encoded callsign
+using meta_t = std::array< uint8_t, 14 >; // Data type for LSF metadata field
+using payload_t = std::array< uint8_t, 16 >; // Data type for frame payload field
+using lich_t = std::array< uint8_t, 12 >; // Data type for Golay(24,12) encoded LICH data
+
+
+/**
+ * This structure provides bit field definitions for the "TYPE" field
+ * contained in an M17 Link Setup Frame.
+ */
+typedef struct
+{
+ uint16_t stream : 1; //< Packet/stream indicator: 0 = packet, 1 = stream
+ uint16_t dataType : 2; //< Data type indicator
+ uint16_t encType : 2; //< Encryption type
+ uint16_t encSubType : 2; //< Encryption subtype
+ uint16_t CAN : 4; //< Channel Access Number
+ uint16_t : 4; //< Reserved, padding to 16 bit
+}
+__attribute__((packed)) streamType_t;
+
+
+/**
+ * Data structure corresponding to a full M17 Link Setup Frame.
+ */
+typedef struct
+{
+ call_t dst; //< Destination callsign
+ call_t src; //< Source callsign
+ streamType_t type; //< Stream type information
+ meta_t meta; //< Metadata
+ uint16_t crc; //< CRC
+}
+__attribute__((packed)) lsf_t;
+
+
+/**
+ * Data structure corresponding to a full M17 data frame.
+ */
+typedef struct
+{
+ uint16_t frameNum; //< Frame number
+ payload_t payload; //< Payload data
+}
+__attribute__((packed)) dataFrame_t;
+
+#endif /* M17DATATYPES_H */
diff --git a/openrtx/include/protocols/M17/M17Frame.h b/openrtx/include/protocols/M17/M17Frame.h
new file mode 100644
index 00000000..5602c321
--- /dev/null
+++ b/openrtx/include/protocols/M17/M17Frame.h
@@ -0,0 +1,118 @@
+/***************************************************************************
+ * Copyright (C) 2021 by Federico Amedeo Izzo IU2NUO, *
+ * Niccolò Izzo IU2KIN *
+ * Frederik Saraci IU2NRO *
+ * Silvano Seva IU2KWO *
+ * *
+ * 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 3 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, see *
+ ***************************************************************************/
+
+#ifndef M17FRAME_H
+#define M17FRAME_H
+
+#ifndef __cplusplus
+#error This header is C++ only!
+#endif
+
+#include
+#include
+#include "M17Datatypes.h"
+
+/**
+ * This class describes and handles a generic M17 data frame.
+ */
+class M17Frame
+{
+public:
+
+ /**
+ * Constructor.
+ */
+ M17Frame()
+ {
+ clear();
+ }
+
+ /**
+ * Destructor.
+ */
+ ~M17Frame(){ }
+
+ /**
+ * Clear the frame content, filling it with zeroes.
+ */
+ void clear()
+ {
+ memset(&data, 0x00, sizeof(dataFrame_t));
+ }
+
+ /**
+ * Set frame sequence number.
+ *
+ * @param seqNum: frame number, between 0 and 0x7FFF.
+ */
+ void setFrameNumber(const uint16_t seqNum)
+ {
+ // NOTE: M17 fields are big-endian, we need to swap bytes
+ data.frameNum = __builtin_bswap16(seqNum & 0x7fff);
+ }
+
+ /**
+ * Mark this frame as the last one in the transmission, informing the
+ * receiver that transmission ends.
+ */
+ void lastFrame()
+ {
+ data.frameNum |= 0x0080;
+ }
+
+ /**
+ * Access frame payload.
+ *
+ * @return a reference to frame's paylod field, allowing for both read and
+ * write access.
+ */
+ payload_t& payload()
+ {
+ return data.payload;
+ }
+
+ /**
+ * Get underlying data structure.
+ *
+ * @return a reference to the underlying dataFrame_t data structure.
+ */
+ dataFrame_t& getData()
+ {
+ return data;
+ }
+
+ /**
+ * Dump the frame content to a std::array.
+ *
+ * \return std::array containing the content of the frame.
+ */
+ std::array< uint8_t, sizeof(dataFrame_t) > toArray()
+ {
+ std::array< uint8_t, sizeof(dataFrame_t) > frame;
+ memcpy(frame.data(), &data, frame.size());
+ return frame;
+ }
+
+private:
+
+ dataFrame_t data; ///< Underlying frame data.
+};
+
+#endif /* M17FRAME_H */
diff --git a/openrtx/include/protocols/M17/M17LinkSetupFrame.h b/openrtx/include/protocols/M17/M17LinkSetupFrame.h
new file mode 100644
index 00000000..b554417b
--- /dev/null
+++ b/openrtx/include/protocols/M17/M17LinkSetupFrame.h
@@ -0,0 +1,128 @@
+/***************************************************************************
+ * Copyright (C) 2021 by Federico Amedeo Izzo IU2NUO, *
+ * Niccolò Izzo IU2KIN *
+ * Frederik Saraci IU2NRO *
+ * Silvano Seva IU2KWO *
+ * *
+ * 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 3 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, see *
+ ***************************************************************************/
+
+#ifndef M17LINKSETUPFRAME_H
+#define M17LINKSETUPFRAME_H
+
+#ifndef __cplusplus
+#error This header is C++ only!
+#endif
+
+#include
+#include
+#include "M17Datatypes.h"
+
+/**
+ * This class describes and handles an M17 Link Setup Frame.
+ * By default the frame contains a broadcast destination address, unless a
+ * specific address is set by calling the corresponding function.
+ */
+class M17LinkSetupFrame
+{
+public:
+
+ /**
+ * Constructor.
+ */
+ M17LinkSetupFrame();
+
+ /**
+ * Destructor.
+ */
+ ~M17LinkSetupFrame();
+
+ /**
+ * Clear the frame content, filling it with zeroes and resetting the
+ * destination address to broadcast.
+ */
+ void clear();
+
+ /**
+ * Set source callsign.
+ *
+ * @param callsign: string containing the source callsign.
+ */
+ void setSource(const std::string& callsign);
+
+ /**
+ * Set destination callsign.
+ *
+ * @param callsign: string containing the destination callsign.
+ */
+ void setDestination(const std::string& callsign);
+
+ /**
+ * Get stream type field.
+ *
+ * @return a copy of the frame's tream type field.
+ */
+ streamType_t getType();
+
+ /**
+ * Set stream type field.
+ *
+ * @param type: stream type field to be written.
+ */
+ void setType(streamType_t type);
+
+ /**
+ * Get metadata field.
+ *
+ * @return a reference to frame's metadata field, allowing for both read and
+ * write access.
+ */
+ meta_t& metadata();
+
+ /**
+ * Compute a new CRC over the frame content and update the corresponding
+ * field.
+ */
+ void updateCrc();
+
+ /**
+ * Get underlying data structure.
+ *
+ * @return a reference to the underlying dataFrame_t data structure.
+ */
+ lsf_t& getData();
+
+ /**
+ * Dump the frame content to a std::array.
+ *
+ * \return std::array containing the content of the frame.
+ */
+ std::array< uint8_t, sizeof(lsf_t) > toArray();
+
+private:
+
+ /**
+ * Compute the CRC16 of a given chunk of data using the polynomial 0x5935
+ * with an initial value set to 0xFFFF, as per M17 specification.
+ *
+ * \param data: pointer to the data block.
+ * \param len: lenght of the data block, in bytes.
+ * \return computed CRC16 over the data block.
+ */
+ uint16_t crc16(const void *data, const size_t len);
+
+ lsf_t data; ///< Underlying frame data.
+};
+
+#endif /* M17LINKSETUPFRAME_H */
diff --git a/openrtx/src/protocols/M17/M17Callsign.cpp b/openrtx/src/protocols/M17/M17Callsign.cpp
new file mode 100644
index 00000000..e98e6095
--- /dev/null
+++ b/openrtx/src/protocols/M17/M17Callsign.cpp
@@ -0,0 +1,108 @@
+/***************************************************************************
+ * Copyright (C) 2021 by Federico Amedeo Izzo IU2NUO, *
+ * Niccolò Izzo IU2KIN *
+ * Frederik Saraci IU2NRO *
+ * Silvano Seva IU2KWO *
+ * *
+ * Adapted from original code written by Rob Riggs, Mobilinkd LLC *
+ * *
+ * 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 3 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, see *
+ ***************************************************************************/
+
+#include
+#include
+
+bool encode_callsign(const std::string& callsign, call_t& encodedCall,
+ bool strict)
+{
+ encodedCall.fill(0x00);
+ if(callsign.size() > 9) return false;
+
+ // Encode the characters to base-40 digits.
+ uint64_t encoded = 0;
+
+ for(auto it = callsign.rbegin(); it != callsign.rend(); ++it)
+ {
+ encoded *= 40;
+ if (*it >= 'A' and *it <= 'Z')
+ {
+ encoded += (*it - 'A') + 1;
+ }
+ else if (*it >= '0' and *it <= '9')
+ {
+ encoded += (*it - '0') + 27;
+ }
+ else if (*it == '-')
+ {
+ encoded += 37;
+ }
+ else if (*it == '/')
+ {
+ encoded += 38;
+ }
+ else if (*it == '.')
+ {
+ encoded += 39;
+ }
+ else if (strict)
+ {
+ return false;
+ }
+ }
+
+ auto *ptr = reinterpret_cast< uint8_t *>(&encoded);
+ std::copy(ptr, ptr + 6, encodedCall.rbegin());
+
+ return true;
+}
+
+std::string decode_callsign(const call_t& encodedCall)
+{
+ // First of all, check if encoded address is a broadcast one
+ bool isBroadcast = true;
+ for(auto& elem : encodedCall)
+ {
+ if(elem != 0xFF)
+ {
+ isBroadcast = false;
+ break;
+ }
+ }
+
+ if(isBroadcast) return "BROADCAST";
+
+ /*
+ * Address is not broadcast, decode it.
+ * TODO: current implementation works only on little endian architectures.
+ */
+ static const char charMap[] = "xABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-/.";
+
+ uint64_t encoded = 0;
+ auto p = reinterpret_cast(&encoded);
+ std::copy(encodedCall.rbegin(), encodedCall.rend(), p);
+
+ // Decode each base-40 digit and map them to the appriate character.
+ std::string result;
+ size_t index = 0;
+
+ while(encoded)
+ {
+ result[index++] = charMap[encoded % 40];
+ encoded /= 40;
+ }
+
+ result[index] = '\0';
+
+ return result;
+}
diff --git a/openrtx/src/protocols/M17/M17LinkSetupFrame.cpp b/openrtx/src/protocols/M17/M17LinkSetupFrame.cpp
new file mode 100644
index 00000000..b4a2a4c5
--- /dev/null
+++ b/openrtx/src/protocols/M17/M17LinkSetupFrame.cpp
@@ -0,0 +1,110 @@
+/***************************************************************************
+ * Copyright (C) 2021 by Federico Amedeo Izzo IU2NUO, *
+ * Niccolò Izzo IU2KIN *
+ * Frederik Saraci IU2NRO *
+ * Silvano Seva IU2KWO *
+ * *
+ * 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 3 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, see *
+ ***************************************************************************/
+
+#include
+#include
+#include
+
+M17LinkSetupFrame::M17LinkSetupFrame()
+{
+ clear();
+}
+
+M17LinkSetupFrame::~M17LinkSetupFrame()
+{
+
+}
+
+void M17LinkSetupFrame::clear()
+{
+ memset(&data, 0x00, sizeof(lsf_t));
+ data.dst.fill(0xFF);
+}
+
+void M17LinkSetupFrame::setSource(const std::string& callsign)
+{
+ encode_callsign(callsign, data.src);
+}
+
+void M17LinkSetupFrame::setDestination(const std::string& callsign)
+{
+ encode_callsign(callsign, data.dst);
+}
+
+streamType_t M17LinkSetupFrame::getType()
+{
+ // NOTE: M17 fields are big-endian, we need to swap bytes
+ uint16_t *a = reinterpret_cast< uint16_t* >(&data.type);
+ uint16_t b = __builtin_bswap16(*a);
+ return *reinterpret_cast< streamType_t* >(&b);
+}
+
+void M17LinkSetupFrame::setType(streamType_t type)
+{
+ // NOTE: M17 fields are big-endian, we need to swap bytes
+ uint16_t *a = reinterpret_cast< uint16_t* >(&type);
+ uint16_t b = __builtin_bswap16(*a);
+ data.type = *reinterpret_cast< streamType_t* >(&b);
+}
+
+meta_t& M17LinkSetupFrame::metadata()
+{
+ return data.meta;
+}
+
+void M17LinkSetupFrame::updateCrc()
+{
+ // Compute CRC over the first 28 bytes, then store it in big endian format.
+ uint16_t crc = crc16(&data, 28);
+ data.crc = __builtin_bswap16(crc);
+}
+
+lsf_t& M17LinkSetupFrame::getData()
+{
+ return data;
+}
+
+std::array< uint8_t, sizeof(lsf_t) > M17LinkSetupFrame::toArray()
+{
+ std::array< uint8_t, sizeof(lsf_t) > frame;
+ memcpy(frame.data(), &data, frame.size());
+ return frame;
+}
+
+uint16_t M17LinkSetupFrame::crc16(const void *data, const size_t len)
+{
+ const uint8_t *ptr = reinterpret_cast< const uint8_t *>(data);
+ uint16_t crc = 0xFFFF;
+
+ for(size_t i = 0; i < len; i++)
+ {
+ crc ^= (ptr[i] << 8);
+
+ for(uint8_t j = 0; j < 8; j++)
+ {
+ if(crc & 0x8000)
+ crc = (crc << 1) ^ 0x5935;
+ else
+ crc = (crc << 1);
+ }
+ }
+
+ return crc;
+}