Fully functioning KISS TNC

CHANGELOG.md

@@ -28,8 +28,12 @@ First (more or less) working version.
 ### Added
 - All settings (LoRa and APRS) can now be saved to FLASH.
 - Command added for restarting LoRa radio when settings are alterred: "restart lora"
-- Received LoRa frames can now be converted to propper AX25 frames (needed for KISS TNC functionality)
+- Received LoRa frames can now be converted to proper AX25 frames (needed for KISS TNC functionality)
 - KISS mode works for receiving (LoRa -> USB port)
 - KISS mode for transmitting in early phase of development
 - Can enter KISS mode with command "kiss 1" and exit KISS mode with command "sudo kissparms -p ax0 -x"
 
+## [1.0.4] - 2022-05-13
+
+### Added
+- Fully functioning KISS TNC, but repeater flag could not be tested because LoRa APRS software in general is a mess. It appears that nobody reads the AX.25 standard anymore. This software probably is also not up to spec. But at least I tried! You should too: [http://www.ax25.net/AX25.2.2-Jul%2098-2.pdf](http://www.ax25.net/AX25.2.2-Jul%2098-2.pdf)

src/kiss.cpp

@@ -4,7 +4,7 @@
  * KISS encoder uses two steps:
  * 
  * Step 1: encodes the LoRa APRS frame into an AX.25 frame. DONE
- * Step 2: encapsulates the AX.25 frame into a KISS frame. TODO
+ * Step 2: encapsulates the AX.25 frame into a KISS frame. DONE
  * 
  *  struct aprs_frame {
  *      uint8_t source_address[10];
@@ -27,6 +27,9 @@ uint16_t KissClass::EncodeFrame(struct aprs_frame *aprsframe, struct ax25_frame
     uint16_t cnt=0;
     uint16_t position = 0;
     uint8_t digi_cnt = 0;
+    uint8_t escaped_string_cnt=0;
+    
+    //printf("Encode KISS");
     
     // Destination call
     //printf("Destination: ");
@@ -35,7 +38,7 @@ uint16_t KissClass::EncodeFrame(struct aprs_frame *aprsframe, struct ax25_frame
     while (cnt < 7)
     {
         ax25frame->complete[position] = *(encoded_call+cnt);
-        ////printf("0x%X ", *(encoded_call+cnt));
+        //printf("0x%X ", *(encoded_call+cnt));
         //printf("0x%X ", ax25frame->complete[position]);
         cnt++;
         position++;
@@ -49,7 +52,7 @@ uint16_t KissClass::EncodeFrame(struct aprs_frame *aprsframe, struct ax25_frame
     while (cnt < 7)
     {
         ax25frame->complete[position] = *(encoded_call+cnt);
-        ////printf("0x%X ", *(encoded_call+cnt));
+        //printf("0x%X ", *(encoded_call+cnt));
         //printf("0x%X ", ax25frame->complete[position]);
         cnt++;
         position++;
@@ -73,7 +76,7 @@ uint16_t KissClass::EncodeFrame(struct aprs_frame *aprsframe, struct ax25_frame
             encoded_call = EncodeCall(aprsframe->digis[digi_cnt]);            
             while (cnt < 7) {
                 ax25frame->complete[position] = *(encoded_call+cnt);
-                ////printf("0x%X ", *(encoded_call+cnt));
+                //printf("0x%X ", *(encoded_call+cnt));
                 //printf("0x%X ", ax25frame->complete[position]);
                 cnt++;
                 position++;
@@ -109,6 +112,9 @@ uint16_t KissClass::EncodeFrame(struct aprs_frame *aprsframe, struct ax25_frame
     // Encapsulate AX.25 frame in KISS frame (including escaping FEND codes)    
     putchar(FEND);
     putchar(CMD_DATA);
+    escaped_string_cnt=0;
+    ax25frame->encoded_kiss_frame[escaped_string_cnt++] = FEND;
+    ax25frame->encoded_kiss_frame[escaped_string_cnt++] = CMD_DATA;
     cnt=0;
     position=ax25frame->lenght;
     while (position-- != 0)
@@ -117,15 +123,21 @@ uint16_t KissClass::EncodeFrame(struct aprs_frame *aprsframe, struct ax25_frame
         if (ax25frame->complete[cnt] == FEND) {
             putchar(FESC);
             putchar(TFEND);
+            ax25frame->encoded_kiss_frame[escaped_string_cnt++] = FESC;
+            ax25frame->encoded_kiss_frame[escaped_string_cnt++] = TFEND;
         } else if (ax25frame->complete[cnt] == FESC) {
             putchar(FESC);
             putchar(TFESC);
+            ax25frame->encoded_kiss_frame[escaped_string_cnt++] = FESC;
+            ax25frame->encoded_kiss_frame[escaped_string_cnt++] = TFESC;
         } else {
             putchar(ax25frame->complete[cnt]);
+            ax25frame->encoded_kiss_frame[escaped_string_cnt++] = ax25frame->complete[cnt];
         }
         cnt++;
     }
     putchar(FEND);
+    ax25frame->encoded_kiss_frame[escaped_string_cnt++] = FEND;
     //printf("\n");
     
 
@@ -136,13 +148,21 @@ uint16_t KissClass::EncodeFrame(struct aprs_frame *aprsframe, struct ax25_frame
  * Decodes a KISS frame from the usb serial port
  * 
  * Input : string starting with FEND and ending with FEND
- * Output: ax25frame->decoded_kiss_frame terminated with NULL
+ * Output: filled struct AprsFrame
  * Return: 0 = OK, 1 = ERROR, 2 = EXIT KISS MODE
  */
-uint16_t KissClass::DecodeFrame(uint8_t string[], struct ax25_frame *ax25frame)
+uint16_t KissClass::DecodeFrame(uint8_t string[], struct kiss_tx_frame *kisstxframe)
 {
     uint16_t position  =0 ;
+    uint16_t loop_counter = 0;
     uint16_t cnt  =0 ;
+    uint16_t ssid = 0;
+    uint16_t last_digi = 0;
+    uint16_t digi_cnt = 0;
+    
+    //printf("Decode KISS");
+    
+    kisstxframe->valid_data = false;
     
     // Not a valid frame
     if (string[position] != FEND)
@@ -182,6 +202,176 @@ uint16_t KissClass::DecodeFrame(uint8_t string[], struct ax25_frame *ax25frame)
     }
     
     // If we are here we have a valid AX.25 frame in 'string' which is decapsulated from its KISS frame
+    /*
+    0-5 destination
+    6 destination ssid
+    7-12 source
+    13 desitination sidd
+    
+    vanaf byte 13 LAST FLAG zoeken
+    
+    03
+    f0
+    payload tot aan NULL
+    */
+    
+    // Decode destination call
+    position = 0;
+    cnt = 0;
+    loop_counter = 0;
+    while (loop_counter < 6)
+    {
+        kisstxframe->digis[0][cnt] = string[position] >> 1;
+        // Remove space
+        if (kisstxframe->digis[0][cnt] == ' ')
+            cnt--;
+        position++;
+        loop_counter++;
+        cnt++;
+        //printf("%u ", position);
+    }
+    
+    // Extract SSID
+    //printf("position: %u\n", position);
+    ssid = (string[position] & 0b00011110) >> 1;
+    //printf("DIGI SSID: %u (%u)\n", ssid, position);
+    
+    // Place SSID behind call or not if it is zero
+    if (ssid != 0) {
+        kisstxframe->digis[0][cnt++] = '-';
+        if (ssid < 10)
+        {
+            kisstxframe->digis[0][cnt++] = ssid + 48;
+        }
+        else
+        {
+            kisstxframe->digis[0][cnt++] = '1';
+            kisstxframe->digis[0][cnt++] = (ssid%10)+48;
+        }
+    }
+    // Is has-been-repeated flag set?
+    if(string[position] & 0b10000000) {
+        kisstxframe->digis[0][cnt] = '*';
+        cnt++;
+    }
+    kisstxframe->digis[0][cnt] = 0;   //terminate string
+    position++;
+    
+    // Decode source call
+    cnt = 0;
+    loop_counter=0;
+    while (loop_counter < 6)
+    {
+        kisstxframe->source_address[cnt] = string[position] >> 1;
+        // Remove space
+        if (kisstxframe->source_address[cnt] == ' ')
+            cnt--;
+        position++;
+        loop_counter++;
+        cnt++;
+        //printf("%u ", position);
+    }
+    
+    // Extract SSID
+    ssid = (string[position] & 0b00011110) >> 1;
+    //printf("sources SSID: %u (%u)\n", ssid, position);
+    
+   // Place SSID behind call or not if it is zero
+    if (ssid != 0) {
+        kisstxframe->source_address[cnt++] = '-';
+        if (ssid < 10)
+        {
+            kisstxframe->source_address[cnt++] = ssid + 48;
+        }
+        else
+        {
+            kisstxframe->source_address[cnt++] = '1';
+            kisstxframe->source_address[cnt++] = (ssid%10)+48;
+        }
+    }
+    // Is has-been-repeated flag set?
+    if(string[position] & 0b10000000) {
+        kisstxframe->source_address[cnt] = '*';
+        cnt++;
+    }
+    kisstxframe->source_address[cnt] = 0;   //terminate string
+    
+    // Check LAST flag
+    if ( (string[position] & 0b00000001))
+        last_digi = 1;
+    
+    position++;
+     
+    // Decode digi path
+    digi_cnt=1;
+    while (last_digi == 0) {
+        
+        cnt = 0;
+        loop_counter=0;
+        while (loop_counter < 6)
+        {
+            kisstxframe->digis[digi_cnt][cnt] = string[position] >> 1;
+            // Remove space
+            if (kisstxframe->digis[digi_cnt][cnt] == ' ')
+                cnt--;
+            position++;
+            loop_counter++;
+            cnt++;
+            //printf("%u ", position);
+        }
+        
+        // Extract SSID
+        ssid = (string[position] & 0b00011110) >> 1;
+        //printf("DIGI  SSID: %u (%u)\n", ssid, position);
+        
+        // Place SSID behind call or not if it is zero
+        if (ssid != 0) {
+            kisstxframe->digis[digi_cnt][cnt++] = '-';
+            if (ssid < 10)
+            {
+                kisstxframe->digis[digi_cnt][cnt++] = ssid + 48;
+            }
+            else
+            {
+                kisstxframe->digis[digi_cnt][cnt++] = '1';
+                kisstxframe->digis[digi_cnt][cnt++] = (ssid%10) + 48;
+            }
+        }
+     
+        // Is has-been-repeated flag set?
+        if(string[position] & 0b10000000) {
+            kisstxframe->digis[digi_cnt][cnt] = '*';
+            cnt++;
+        }
+        kisstxframe->digis[digi_cnt][cnt] = 0;   //terminate string
+        
+        // Check LAST flag (also ends when more than 10 digis)
+        if ( (string[position] & 0b00000001) || digi_cnt > 8)
+            last_digi = 1;
+    
+        digi_cnt++;
+        position++;
+    }
+    kisstxframe->number_of_digipeaters = digi_cnt-1;
+    //printf("Digipeaters: %u \n",kisstxframe->number_of_digipeaters );
+    
+    //Skip the two control fields
+    position++;
+    position++;
+   
+    //Rest of string up to NULL is payload
+    cnt = 0;
+    kisstxframe->data_field[cnt++] = ':';
+    while (string[position] != 0 && position < 512)
+    {
+        kisstxframe->data_field[cnt] = string[position];
+        position++;
+        cnt++;
+    }
+    kisstxframe->data_field[cnt] = 0;     //terminate string
+    
+    kisstxframe->valid_data = true;
+    
     
     return 0;
 }
@@ -197,10 +387,26 @@ uint8_t * KissClass::EncodeCall(uint8_t string[])
 {
     uint8_t position = 0;
     uint8_t cnt = 0;
+    uint8_t repeat_flag = 0;
     
     static uint8_t call[7] = { 0,0,0,0,0,0,0} ;
     uint8_t ssid = 0;
     
+    // if asterix is pressent in string, than the message has been repeated, so set the 'has been repeated' flag in the ssid register
+    // At the same time delete the asterix and place a NULL (string terminator) at its place. As the asterix should be the last character in the string, this should work.
+    position = 0;
+    while( string[position] != 0)
+    {
+        if (string[position] == '*') {
+            repeat_flag = 1;
+            string[position] == 0;
+            break;
+        }
+        
+        position++;
+    }
+    
+    position = 0;
     // extract call
     while( string[position] != 0 || cnt < 6)
     {
@@ -229,17 +435,11 @@ uint8_t * KissClass::EncodeCall(uint8_t string[])
         }
     }
     
-    // if asterix is pressent in string, than the message has been repeated, so set the 'has been repeated' flag in the ssid register
-    position = 0;
-    while( string[position] != 0)
-    {
-        if (string[position] == '*')
-            ssid = 0b10000000;
-        
-        position++;
-    }
+    ssid = ssid << 1;
+    ssid |= 0b01100000;
     
-    ssid = (ssid << 1) | 0b01100000;
+    if (repeat_flag == 1)            
+        ssid |= 0b10000000;
     
     // add encoded ssid to encoded call array
     call[6] = ssid;

src/kiss.h

@@ -39,15 +39,27 @@
     struct ax25_frame {
         uint8_t complete[512];
         uint16_t lenght = 0;
+        uint8_t encoded_kiss_frame[512];
         uint8_t decoded_kiss_frame[512];
         uint16_t kiss_length = 0;
     };
     
+    struct kiss_tx_frame {
+        uint8_t source_address[10];
+        uint8_t data_field[512];
+        uint8_t digis[10][10];
+        uint16_t number_of_digipeaters = 0;
+        
+        uint8_t lora_string[512];
+        
+        uint8_t valid_data = false;
+    };
+
   class KissClass
   {
   public:
       uint16_t EncodeFrame(struct aprs_frame *frame, struct ax25_frame *ax25frame);
-      uint16_t DecodeFrame(uint8_t string[], struct ax25_frame *ax25frame);
+      uint16_t DecodeFrame(uint8_t string[], struct kiss_tx_frame *kisstxframe);
   private:
       uint8_t * EncodeCall(uint8_t string[]);
   };

src/main.cpp

@@ -12,6 +12,8 @@
 
 KissClass Kiss;
 struct ax25_frame AX25Frame;        //defined in kiss.h
+struct aprs_frame AprsFrame;        //defined in kiss.h
+struct kiss_tx_frame KissTxFrame;   //defined in kiss.h
 
 bool startRadio();
 void getPacketData(int packetLength);
@@ -23,6 +25,7 @@ uint16_t decode_packet ();
 
 /* declaration for transmit functions */
 void ComposeAprsFrame(uint8_t payload[]);
+void ComposeAprsFrameFromKiss();
 bool TransmitRequest = false;
 void transmit();
 
@@ -433,6 +436,7 @@ void ReadUSBSerial(void)
     static char strg[512];
     int chr;
     static int lp = 0;
+    uint16_t tmp;
     
     if (Status.KissMode == OFF) {
         // Read serial port (USB) - non-blocking!
@@ -472,15 +476,21 @@ void ReadUSBSerial(void)
             // Received FEND (=begin or end frame)
             if(chr == FEND)
             {
-                // Valid FISS frame received
+                // Valid KISS frame received
                 if (strg[0] == FEND && lp > 1)
                 {
-                    if (Kiss.DecodeFrame((uint8_t *) strg, &AX25Frame) == 2)
+                    tmp = Kiss.DecodeFrame((uint8_t *) strg, &KissTxFrame);
+                    if ( tmp == 2)
                     {
                         //exit KISS MODE
                         stdio_set_translate_crlf(&stdio_usb, true);
                         Status.KissMode = OFF; 
                     }
+                    // Valid KISS data frame, so lets send it
+                    else if (tmp == 0)
+                    {
+                        ComposeAprsFrameFromKiss();
+                    }
                     lp = 0;		//reset string buffer pointer
                 }
                 // We received a FEND byte,so we are probably between two KISS frames. Let's assume the latest FEND is the beginning of a new frame
@@ -682,8 +692,6 @@ uint16_t decode_packet ()
     int position = 0;
     int cnt = 0;
     
-    struct aprs_frame AprsFrame;  //defined in kiss.h
-
     memset(AprsFrame.source_address, 0, sizeof(AprsFrame.source_address));
     memset(AprsFrame.digi_path, 0, sizeof(AprsFrame.digi_path));
     memset(AprsFrame.data_field, 0, sizeof(AprsFrame.data_field));
@@ -809,8 +817,11 @@ uint16_t decode_packet ()
         log_out("Source address: %s\nDigipeaters (%u): %s %s %s %s\nData: %s\n", AprsFrame.source_address, AprsFrame.number_of_digipeaters+1, AprsFrame.digis[0], AprsFrame.digis[1], AprsFrame.digis[2], AprsFrame.digis[3], AprsFrame.data_field);
         
         // If in KISS mode the struct AprsFrame is handed over to the KISS encoder
-        if (Status.KissMode == ON)
+        if (Status.KissMode == ON) {
             Kiss.EncodeFrame(&AprsFrame, &AX25Frame);
+            //if (Kiss.DecodeFrame(AX25Frame.encoded_kiss_frame, &KissTxFrame) == 0)
+                //ComposeAprsFrameFromKiss();
+        }
         
         if (AprsFrame.message[0])
         {
@@ -960,6 +971,61 @@ void ComposeAprsFrame(uint8_t payload[])
     log_out("%s\n", txBuffer);
 }
 
+void ComposeAprsFrameFromKiss()
+{
+    uint16_t BufferPosition = 0;
+    uint16_t cnt = 0;
+    uint8_t digi_cnt=0;
+    
+    log_out( "Compose APRS from KISS frame");
+    
+    memset(txBuffer, 0, sizeof(txBuffer));
+    
+    // APRS header
+    txBuffer[BufferPosition++] = '<';
+    txBuffer[BufferPosition++] = 0xff;
+    txBuffer[BufferPosition++] = 0x01;
+    
+    while ( KissTxFrame.source_address[cnt] != 0 && BufferPosition<MTU )
+    {
+        txBuffer[BufferPosition] = KissTxFrame.source_address[cnt];
+        BufferPosition++;
+        cnt++;
+    }
+    txBuffer[BufferPosition++] = '>';
+    
+    digi_cnt=0;
+    while(digi_cnt <= KissTxFrame.number_of_digipeaters) {
+        cnt=0;
+        
+        while ( KissTxFrame.digis[digi_cnt][cnt] != 0 && BufferPosition<MTU )
+        {
+            txBuffer[BufferPosition++] = KissTxFrame.digis[digi_cnt][cnt];
+            cnt++;
+        }
+        txBuffer[BufferPosition++] = ',';
+        digi_cnt++;
+    }
+    
+    // Overwrite last command with colon
+    txBuffer[--BufferPosition] = ':';
+    
+    cnt=0;
+    while ( KissTxFrame.data_field[cnt] != 0 && BufferPosition<MTU )
+    {
+        txBuffer[BufferPosition++] = KissTxFrame.data_field[cnt];
+        cnt++;
+    }
+    
+    // Set variable to indicate a send request
+    TransmitRequest = true; 
+    
+    // Ready for next input KISS frame.
+    KissTxFrame.valid_data = false;
+    
+    log_out("%s\n", txBuffer);
+}
+
 void transmit() {
   uint16_t position = 0;