AX25.h

#if !defined(_RADIOLIB_AX25_H)
#define _RADIOLIB_AX25_H

#include "../../TypeDef.h"

#if !defined(RADIOLIB_EXCLUDE_AX25)

#include "../PhysicalLayer/PhysicalLayer.h"
#include "../AFSK/AFSK.h"

// macros to access bits in byte array, from http://www.mathcs.emory.edu/~cheung/Courses/255/Syllabus/1-C-intro/bit-array.html
#define SET_BIT_IN_ARRAY(A, k)                        ( A[(k/8)] |= (1 << (k%8)) )
#define CLEAR_BIT_IN_ARRAY(A, k)                      ( A[(k/8)] &= ~(1 << (k%8)) )
#define TEST_BIT_IN_ARRAY(A, k)                       ( A[(k/8)] & (1 << (k%8)) )
#define GET_BIT_IN_ARRAY(A, k)                        ( (A[(k/8)] & (1 << (k%8))) ? 1 : 0 )

// CRC-CCITT calculation macros
#define XOR(A, B)                                     ( ((A) || (B)) && !((A) && (B)) )
#define CRC_CCITT_POLY                                0x1021      //  generator polynomial
#define CRC_CCITT_POLY_REVERSED                       0x8408      //  CRC_CCITT_POLY in reversed bit order
#define CRC_CCITT_INIT                                0xFFFF      //  initial value

// maximum callsign length in bytes
#define AX25_MAX_CALLSIGN_LEN                         6

// flag field                                                         MSB   LSB   DESCRIPTION
#define AX25_FLAG                                     0b01111110  //  7     0     AX.25 frame start/end flag

// address field
#define AX25_SSID_COMMAND_DEST                        0b10000000  //  7     7     frame type: command (set in destination SSID)
#define AX25_SSID_COMMAND_SOURCE                      0b00000000  //  7     7                 command (set in source SSID)
#define AX25_SSID_RESPONSE_DEST                       0b00000000  //  7     7                 response (set in destination SSID)
#define AX25_SSID_RESPONSE_SOURCE                     0b10000000  //  7     7                 response (set in source SSID)
#define AX25_SSID_HAS_NOT_BEEN_REPEATED               0b00000000  //  7     7                 not repeated yet (set in repeater SSID)
#define AX25_SSID_HAS_BEEN_REPEATED                   0b10000000  //  7     7                 repeated (set in repeater SSID)
#define AX25_SSID_RESERVED_BITS                       0b01100000  //  6     5     reserved bits in SSID
#define AX25_SSID_HDLC_EXTENSION_CONTINUE             0b00000000  //  0     0     HDLC extension bit: next octet contains more address information
#define AX25_SSID_HDLC_EXTENSION_END                  0b00000001  //  0     0                         address field end

// control field
#define AX25_CONTROL_U_SET_ASYNC_BAL_MODE             0b01101100  //  7     2     U frame type: set asynchronous balanced mode (connect request)
#define AX25_CONTROL_U_SET_ASYNC_BAL_MODE_EXT         0b00101100  //  7     2                   set asynchronous balanced mode extended (connect request with module 128)
#define AX25_CONTROL_U_DISCONNECT                     0b01000000  //  7     2                   disconnect request
#define AX25_CONTROL_U_DISCONNECT_MODE                0b00001100  //  7     2                   disconnect mode (system busy or disconnected)
#define AX25_CONTROL_U_UNNUMBERED_ACK                 0b01100000  //  7     2                   unnumbered acknowledge
#define AX25_CONTROL_U_FRAME_REJECT                   0b10000100  //  7     2                   frame reject
#define AX25_CONTROL_U_UNNUMBERED_INFORMATION         0b00000000  //  7     2                   unnumbered information
#define AX25_CONTROL_U_EXHANGE_IDENTIFICATION         0b10101100  //  7     2                   exchange ID
#define AX25_CONTROL_U_TEST                           0b11100000  //  7     2                   test
#define AX25_CONTROL_POLL_FINAL_ENABLED               0b00010000  //  4     4     control field poll/final bit: enabled
#define AX25_CONTROL_POLL_FINAL_DISABLED              0b00000000  //  4     4                                   disabled
#define AX25_CONTROL_S_RECEIVE_READY                  0b00000000  //  3     2     S frame type: receive ready (system ready to receive)
#define AX25_CONTROL_S_RECEIVE_NOT_READY              0b00000100  //  3     2                   receive not ready (TNC buffer full)
#define AX25_CONTROL_S_REJECT                         0b00001000  //  3     2                   reject (out of sequence or duplicate)
#define AX25_CONTROL_S_SELECTIVE_REJECT               0b00001100  //  3     2                   selective reject (single frame repeat request)
#define AX25_CONTROL_INFORMATION_FRAME                0b00000000  //  0     0     frame type: information (I frame)
#define AX25_CONTROL_SUPERVISORY_FRAME                0b00000001  //  1     0                 supervisory (S frame)
#define AX25_CONTROL_UNNUMBERED_FRAME                 0b00000011  //  1     0                 unnumbered (U frame)

// protocol identifier field
#define AX25_PID_ISO_8208                             0x01
#define AX25_PID_TCP_IP_COMPRESSED                    0x06
#define AX25_PID_TCP_IP_UNCOMPRESSED                  0x07
#define AX25_PID_SEGMENTATION_FRAGMENT                0x08
#define AX25_PID_TEXNET_DATAGRAM_PROTOCOL             0xC3
#define AX25_PID_LINK_QUALITY_PROTOCOL                0xC4
#define AX25_PID_APPLETALK                            0xCA
#define AX25_PID_APPLETALK_ARP                        0xCB
#define AX25_PID_ARPA_INTERNET_PROTOCOL               0xCC
#define AX25_PID_ARPA_ADDRESS_RESOLUTION              0xCD
#define AX25_PID_FLEXNET                              0xCE
#define AX25_PID_NET_ROM                              0xCF
#define AX25_PID_NO_LAYER_3                           0xF0
#define AX25_PID_ESCAPE_CHARACTER                     0xFF

// AFSK tones in Hz
#define AX25_AFSK_MARK                                1200
#define AX25_AFSK_SPACE                               2200

// tone duration in us (for 1200 baud AFSK)
#define AX25_AFSK_TONE_DURATION                       833

class AX25Frame {
  public:
    char destCallsign[AX25_MAX_CALLSIGN_LEN + 1];

    uint8_t destSSID;

    char srcCallsign[AX25_MAX_CALLSIGN_LEN + 1];

    uint8_t srcSSID;

    uint8_t numRepeaters;

    uint8_t control;

    uint8_t protocolID;

    uint16_t infoLen;

    uint8_t rcvSeqNumber;

    uint16_t sendSeqNumber;

    #ifndef RADIOLIB_STATIC_ONLY

      uint8_t* info;

      char** repeaterCallsigns;

      uint8_t* repeaterSSIDs;
    #else

      uint8_t info[RADIOLIB_STATIC_ARRAY_SIZE];

      char repeaterCallsigns[8][AX25_MAX_CALLSIGN_LEN + 1];

      uint8_t repeaterSSIDs[8];
    #endif

    AX25Frame(const char* destCallsign, uint8_t destSSID, const char* srcCallsign, uint8_t srcSSID, uint8_t control);

    AX25Frame(const char* destCallsign, uint8_t destSSID, const char* srcCallsign, uint8_t srcSSID, uint8_t control, uint8_t protocolID, const char* info);

    AX25Frame(const char* destCallsign, uint8_t destSSID, const char* srcCallsign, uint8_t srcSSID, uint8_t control, uint8_t protocolID, uint8_t* info, uint16_t infoLen);

    AX25Frame(const AX25Frame& frame);

    ~AX25Frame();

    AX25Frame& operator=(const AX25Frame& frame);

    int16_t setRepeaters(char** repeaterCallsigns, uint8_t* repeaterSSIDs, uint8_t numRepeaters);

    void setRecvSequence(uint8_t seqNumber);

    void setSendSequence(uint8_t seqNumber);
};

class AX25Client {
  public:
    explicit AX25Client(PhysicalLayer* phy);

    #if !defined(RADIOLIB_EXCLUDE_AFSK)

    explicit AX25Client(AFSKClient* audio);
    #endif

    // basic methods

    int16_t begin(const char* srcCallsign, uint8_t srcSSID = 0x00, uint8_t preambleLen = 8);

    int16_t transmit(const char* str, const char* destCallsign, uint8_t destSSID = 0x00);

    int16_t sendFrame(AX25Frame* frame);

#ifndef RADIOLIB_GODMODE
  private:
#endif
    PhysicalLayer* _phy;
    #if !defined(RADIOLIB_EXCLUDE_AFSK)
    AFSKClient* _audio;
    #endif

    char _srcCallsign[AX25_MAX_CALLSIGN_LEN + 1] = {0, 0, 0, 0, 0, 0, 0};
    uint8_t _srcSSID = 0;
    uint16_t _preambleLen = 0;

    static uint16_t getFrameCheckSequence(uint8_t* buff, size_t len);
    static uint8_t flipBits(uint8_t b);
    static uint16_t flipBits16(uint16_t i);
};

#endif

#endif