KISS receive works, transmit in early phase of development.

CHANGELOG.md

@@ -29,4 +29,7 @@ First (more or less) working version.
 - 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)
+- 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"
 

src/kiss.cpp

@@ -70,8 +70,8 @@ uint16_t KissClass::EncodeFrame(struct aprs_frame *aprsframe, struct ax25_frame
         digi_cnt = 1;       // Start at position 1 as position 0 contains destination (which we already encoded)
         while (aprsframe->number_of_digipeaters-- != 0) {
             
+            encoded_call = EncodeCall(aprsframe->digis[digi_cnt]);            
             while (cnt < 7) {
-                encoded_call = EncodeCall(aprsframe->digis[digi_cnt]);
                 ax25frame->complete[position] = *(encoded_call+cnt);
                 ////printf("0x%X ", *(encoded_call+cnt));
                 //printf("0x%X ", ax25frame->complete[position]);
@@ -101,21 +101,88 @@ uint16_t KissClass::EncodeFrame(struct aprs_frame *aprsframe, struct ax25_frame
         cnt++;
         position++;
     }
-    printf( "\n");
+    //printf( "\n");
     
     // Store length of AX25 frame
     ax25frame->lenght = position;
     
-    /*cnt=0;
-    while (ax25frame->lenght-- != 0)
+    // Encapsulate AX.25 frame in KISS frame (including escaping FEND codes)    
+    putchar(FEND);
+    putchar(CMD_DATA);
+    cnt=0;
+    position=ax25frame->lenght;
+    while (position-- != 0)
     {
-        printf("0x%X ", ax25frame->complete[cnt]);
+        // Escape FESC and TFEND
+        if (ax25frame->complete[cnt] == FEND) {
+            putchar(FESC);
+            putchar(TFEND);
+        } else if (ax25frame->complete[cnt] == FESC) {
+            putchar(FESC);
+            putchar(TFESC);
+        } else {
+            putchar(ax25frame->complete[cnt]);
+        }
         cnt++;
     }
-    printf("\n");
-    */
+    putchar(FEND);
+    //printf("\n");
+    
 
-    //fwrite(ax25frame->complete, 1, ax25frame->lenght, stdout);
+    return 0;
+}
+
+/*
+ * 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
+ * Return: 0 = OK, 1 = ERROR, 2 = EXIT KISS MODE
+ */
+uint16_t KissClass::DecodeFrame(uint8_t string[], struct ax25_frame *ax25frame)
+{
+    uint16_t position  =0 ;
+    uint16_t cnt  =0 ;
+    
+    // Not a valid frame
+    if (string[position] != FEND)
+        return 1;
+    
+    position++;
+    
+    // Is data frame: we de-escape the string and put it back in the same string with a NULL at the end as terminator.
+    if (string[position] == CMD_DATA)
+    {
+        position++;
+        while (string[position] != FEND)
+        {
+            // De-escape codes
+            if (string[position] == FESC && string[position+1] == TFEND)
+            {
+                string[cnt] = FEND;
+                position++;
+            }
+            else if (string[position] == FESC && string[position+1] == TFESC)
+            {
+                string[cnt] = FESC;
+                position++;
+            }
+            else {
+                string[cnt] = string[position];
+            }
+            cnt++;
+            position++;
+        }
+       string[cnt] = 0;             //Terminate string
+        
+    }
+    // Is command to exit KISS MODE
+    else if (string[position] == CMD_EXIT_KISS) {
+        return 2;
+    }
+    
+    // If we are here we have a valid AX.25 frame in 'string' which is decapsulated from its KISS frame
+    
     return 0;
 }
 
@@ -137,11 +204,13 @@ uint8_t * KissClass::EncodeCall(uint8_t string[])
     // extract call
     while( string[position] != 0 || cnt < 6)
     {
-        call[cnt++] = string[position] << 1;
         if ( string[position] == '-') {
             position++;
             break;
+        } else {
+            call[cnt] = string[position] << 1;            
         }
+        cnt++;
         position++;
     }
     // pad with spaces to a length of 6

src/kiss.h

@@ -39,13 +39,15 @@
     struct ax25_frame {
         uint8_t complete[512];
         uint16_t lenght = 0;
-        uint8_t kiss_frame[512];
+        uint8_t decoded_kiss_frame[512];
+        uint16_t kiss_length = 0;
     };
 
   class KissClass
   {
   public:
       uint16_t EncodeFrame(struct aprs_frame *frame, struct ax25_frame *ax25frame);
+      uint16_t DecodeFrame(uint8_t string[], struct ax25_frame *ax25frame);
   private:
       uint8_t * EncodeCall(uint8_t string[]);
   };

src/main.cpp

@@ -11,6 +11,7 @@
 #include "hardware/claim.h"
 
 KissClass Kiss;
+struct ax25_frame AX25Frame;  //defined in kiss.h
 
 bool startRadio();
 void getPacketData(int packetLength);
@@ -429,31 +430,72 @@ void ProcessSerialInput(char string[])
 }
 void ReadUSBSerial(void)
 {
-    static char strg[100];
+    static char strg[512];
     int chr;
     static int lp = 0;
     
-    // Read serial port (USB) - non-blocking!
-    chr = getchar_timeout_us(0);
-	while(chr != PICO_ERROR_TIMEOUT)
-	{
-		log_out("%c", chr);
-        
-        strg[lp++] = chr;
-		if(chr == CR || lp == (sizeof(strg) - 1))
-		{
-			strg[lp-1] = 0;	//terminate string by overwriting <CR> with NULL
-			//log_out("You wrote - %s\n", strg);
-			lp = 0;		//reset string buffer pointer
-			log_out("\n");
-			
-			ProcessSerialInput(strg);
+    if (Status.KissMode == OFF) {
+        // Read serial port (USB) - non-blocking!
+        chr = getchar_timeout_us(0);
+        while(chr != PICO_ERROR_TIMEOUT)
+        {
+            log_out("%c", chr);
             
-			break;
-		}
+            strg[lp++] = chr;
+            if(chr == CR || lp == (sizeof(strg) - 1))
+            {
+                strg[lp-1] = 0;	//terminate string by overwriting <CR> with NULL
+                //log_out("You wrote - %s\n", strg);
+                lp = 0;		//reset string buffer pointer
+                log_out("\n");
+                
+                ProcessSerialInput(strg);
+                
+                break;
+            }
 
-		chr = getchar_timeout_us(0);
-	}
+            chr = getchar_timeout_us(0);
+        }
+    }
+    // We are in KISS mode
+    else
+    {
+        // Read serial port (USB) - non-blocking!
+        chr = getchar_timeout_us(0);
+        while(chr != PICO_ERROR_TIMEOUT)
+        {
+            strg[lp++] = chr;
+            // Receive buffer buffer full
+            if( lp == (sizeof(strg) - 1)) {
+                lp=0;
+            }
+            // Received FEND (=begin or end frame)
+            if(chr == FEND)
+            {
+                // Valid FISS frame received
+                if (strg[0] == FEND && lp > 1)
+                {
+                    if (Kiss.DecodeFrame((uint8_t *) strg, &AX25Frame) == 2)
+                    {
+                        //exit KISS MODE
+                        stdio_set_translate_crlf(&stdio_usb, true);
+                        Status.KissMode = OFF; 
+                    }
+                    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
+                else
+                {
+                    strg[0] = chr;
+                    lp = 1;         // set string buffer pointer to second position
+                }
+
+                break;
+            }
+
+            chr = getchar_timeout_us(0);
+        }
+    }
 }
 
 int main() {
@@ -641,7 +683,6 @@ uint16_t decode_packet ()
     int cnt = 0;
     
     struct aprs_frame AprsFrame;  //defined in kiss.h
-    struct ax25_frame AX25Frame;  //defined in kiss.h
 
     memset(AprsFrame.source_address, 0, sizeof(AprsFrame.source_address));
     memset(AprsFrame.digi_path, 0, sizeof(AprsFrame.digi_path));
@@ -768,7 +809,7 @@ 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 == 0)
+        if (Status.KissMode == ON)
             Kiss.EncodeFrame(&AprsFrame, &AX25Frame);
         
         if (AprsFrame.message[0])