Decoding APRS frames finished, started with transmitting frames.

Committer: marcel <marcel@hampi.pe1rxf>

src/Config.h

@@ -28,7 +28,7 @@
   int       loraPreamble        = 8;
   int       loraCodingRate      = 5;
   int       loraTxPower         = 17;
-  int       LoRaPaSelect        = 1;
+  int       LoRaPaSelect        = 0;
   uint32_t  loraBandwidth       = 125E3;
   uint32_t  loraFrequency       = 433775000;
 
@@ -57,4 +57,14 @@
   const uint8_t SIG_SYNCED = 0x02;
   const uint8_t RX_ONGOING = 0x04;
   
+  struct aprssettings {
+      uint8_t MyCall[10] = { 'P','E','1','R','X','F','-','5', 0} ;
+      uint8_t ServerCall[10] = { 'P','E','1','R','X','F','-','3', 0} ;
+      uint8_t Destination[10] = { 'A','P','Z','M','D','M', 0} ;
+      uint8_t Path1[10] = { 0,'I','D','E','1','-', '1', 0} ;
+      uint8_t Path2[10] = { 0,'I','D','E','2','-', '2', 0} ; 
+      
+      uint8_t FirmwareVersion[20] = { 'V','1',',','C','o','n','t','r', 'o','l','l','e','r',' ','0','1', 0} ;
+  } AprsSettings;
+
 #endif

src/main.cpp

@@ -7,12 +7,20 @@
 #include "KISS.h"
 
 bool startRadio();
+bool LoadSettings();
 void getPacketData(int packetLength);
+int compare_strings(uint8_t a[], uint8_t b[]);
+bool is_message_for_me (uint8_t data[], uint8_t mycall[]);
 
-void encode_kiss ();
+uint16_t decode_packet ();
+void ComposeAprsFrame(uint8_t payload[]);
+
+void transmit();
     
 int main() {
     
+    uint16_t ServerCommand = 0;
+  
    /* Among others, this initializes the USB-serial port at 115200bps 8N1 */
    stdio_init_all();
     
@@ -22,6 +30,8 @@ int main() {
     
    sleep_ms(5000);
    
+   LoadSettings();
+
    startRadio();
     
    while (1) {
@@ -40,16 +50,43 @@ int main() {
              }
              rxBuffer[packetSize-3] = 0;
              printf("%s\n", rxBuffer);
-             encode_kiss();
+             ServerCommand = decode_packet();
          } else {
              printf("ERROR: No or corrupted APRS frame.\n");
          }
       }
+      
+      if (ServerCommand) {
+          
+          if (ServerCommand == 1) {
+                ComposeAprsFrame(AprsSettings.FirmwareVersion);
+                // Wait for 100ms before responding
+                sleep_ms(5000);
+                transmit();
+                sleep_ms(5000);
+                transmit();
+                sleep_ms(5000);
+                transmit();
+                sleep_ms(5000);
+                transmit();
+          }
+          ServerCommand = 0;
+      }
   }    
   
   return 0;
 }
 
+/*
+ * Load settings from EEPROM
+ */
+bool LoadSettings()
+{
+    printf("APRS settings:\n");
+    printf("My call: %s\n", AprsSettings.MyCall);
+    printf("Server call: %s\n", AprsSettings.ServerCall);
+    
+}
 /*
  * Initializes the LoRa module with the parameters set in config.h
  */
@@ -95,8 +132,9 @@ void getPacketData(int packetLength)
 
 /* Encode LoRa APRS frame: extract source call, digipeater path and data field. At the same time, check for data corruption
  * 
+ * If frame is a message from the server it returns the command from this server 
  */
-void encode_kiss ()
+uint16_t decode_packet ()
 {
     int position = 0;
     int cnt = 0;
@@ -106,12 +144,18 @@ void encode_kiss ()
     uint8_t aprs_source_address[10];
     uint8_t aprs_digi_path[255];
     uint8_t aprs_data_field[255];
+    uint8_t aprs_message[255];
     uint8_t aprs_digis[10][10];
+    uint8_t aprs_acknowledge_number[255];
+    bool aprs_acknowledge_request = false;
+    uint16_t aprs_server_command = 0;
     
     memset(aprs_source_address, 0, sizeof(aprs_source_address));
     memset(aprs_digi_path, 0, sizeof(aprs_digi_path));
     memset(aprs_data_field, 0, sizeof(aprs_data_field));
+    memset(aprs_message, 0, sizeof(aprs_message));
     memset(aprs_digis, 0, sizeof(aprs_digis));
+    memset(aprs_acknowledge_number, 0, sizeof(aprs_acknowledge_number));
    
     // Extract from address
     cnt = 0;    
@@ -184,8 +228,202 @@ void encode_kiss ()
         aprs_digis[number_of_digipeaters][cnt] = 0;    
     }
     
-    if (valid_apsr_data)
+    if (valid_apsr_data) {
+        
+        // Check if packet comes from our server and if so, check if it is a message for us.
+        if ( !compare_strings(aprs_source_address, AprsSettings.ServerCall) ) {
+
+            if ( is_message_for_me(aprs_data_field, AprsSettings.MyCall) ) 
+            {
+               
+                // Extract aprs message from data field
+                position=11;
+                while( aprs_data_field[position] != 0 )
+                {
+                    aprs_message[position-11] = aprs_data_field[position];
+                    position++;
+                }
+                
+                // Extract command and acknowledge number (if present)
+                cnt = 0;
+                position = 0;
+                while( aprs_message[position] != 0 )
+                {
+                    if ( aprs_message[position] == '{' ) {
+                        aprs_acknowledge_number[cnt++] = ':';
+
+                        while ( AprsSettings.ServerCall[cnt-1] != 0 )
+                        {
+                            aprs_acknowledge_number[cnt] = AprsSettings.ServerCall[cnt-1];
+                            cnt++;
+                        }
+                        //Fill with spaces
+                        while ( cnt<10 )
+                        {
+                            aprs_acknowledge_number[cnt++] = ' ';
+
+                        }
+                        aprs_acknowledge_number[cnt++] = ':';                        
+                        aprs_acknowledge_number[cnt++] = 'a';
+                        aprs_acknowledge_number[cnt++] = 'c';
+                        aprs_acknowledge_number[cnt++] = 'k';
+                        aprs_acknowledge_request = true;
+                    }
+                    // Calculate server command
+                    if (!aprs_acknowledge_request) {
+                        aprs_server_command = 10*aprs_server_command + aprs_message[position]-48;
+                    }
+                    
+                    position++;
+                    if (aprs_acknowledge_request) {
+                        aprs_acknowledge_number[cnt++] = aprs_message[position];
+                    }
+                }
+                aprs_acknowledge_number[cnt] = 0;
+            }
+            
+        }
+        
         printf("Source address: %s\nDigipeaters (%u): %s %s %s %s\nData: %s\n", aprs_source_address, number_of_digipeaters+1, aprs_digis[0], aprs_digis[1], aprs_digis[2], aprs_digis[3], aprs_data_field);
+        if (aprs_message[0])
+        {
+            printf("Message from server: %s (command %u)\n", aprs_message, aprs_server_command);
+            if (aprs_acknowledge_request) {
+                ComposeAprsFrame(aprs_acknowledge_number);
+                // Wait for 100ms before responding with acknowledge
+                sleep_ms(100);
+                transmit();
+                printf("Acknowledge request: %s\n", aprs_acknowledge_number);
+            }
+            
+        }
+
+    }    
     else
         printf("Error decoding APRS frame.");
+    
+    return (aprs_server_command);
+}
+
+/* 
+ * Checks if aprs datafield contains message and if message is for us
+ * 
+ * Returns: 0 if datafield contains no message for us
+ *          1 if datafield contains a message for us 
+ */
+bool is_message_for_me (uint8_t data[], uint8_t mycall[])
+{
+    // A variable to iterate through the strings
+    int i=0;
+
+    if (data[0] == ':' && data[10] == ':')
+    {
+        while( i<9 && mycall[i] != 0 ) {
+            if (data[i+1] != mycall[i]) {
+                return (0);
+            }
+            i++;
+        }
+        return (1);
+    }    
+    return (0);
+}
+
+int compare_strings(uint8_t a[], uint8_t b[])
+{
+    // A variable to iterate through the strings
+    int i = 0;
+
+    while (a[i] == b[i]) 
+    {
+        // If either of the strings reaches the end
+        // we stop the loop
+        if (a[i] == '\0' || b[i] == '\0')
+            break;
+        i++;
+    }
+
+    // We check if both the strings have been compared
+    // till the end or not
+    // If the strings are compared till the end they are equal
+    if (a[i] == '\0' && b[i] == '\0')
+        return 0;
+    else
+    {
+        if(a[i] == '\0') 
+            return -1*(b[i]);
+        else if(b[i] == '\0')
+            return a[i];
+        else
+           return (a[i]-b[i]); 
+    }
+}
+
+void ComposeAprsFrame(uint8_t payload[])
+{
+    uint16_t BufferPosition = 0;
+    uint16_t cnt = 0;
+    
+    // APRS header
+    txBuffer[BufferPosition++] = '<';
+    txBuffer[BufferPosition++] = 0xff;
+    txBuffer[BufferPosition++] = 0x01;
+    
+    while ( AprsSettings.MyCall[cnt] != 0 && BufferPosition<MTU )
+    {
+        txBuffer[BufferPosition++] = AprsSettings.MyCall[cnt];
+        cnt++;
+    }
+    txBuffer[BufferPosition++] = '>';
+    
+    cnt=0;
+    while ( AprsSettings.Destination[cnt] != 0 && BufferPosition<MTU )
+    {
+        txBuffer[BufferPosition++] = AprsSettings.Destination[cnt];
+        cnt++;
+    }
+    
+    if ( AprsSettings.Path1[0] != 0)
+        txBuffer[BufferPosition++] = ',';
+    
+    cnt=0;
+    while ( AprsSettings.Path1[cnt] != 0 && BufferPosition<MTU )
+    {
+        txBuffer[BufferPosition++] = AprsSettings.Path1[cnt];
+        cnt++;
+    }
+
+    if ( AprsSettings.Path2[0] != 0)
+        txBuffer[BufferPosition++] = ',';
+
+    cnt=0;
+    while ( AprsSettings.Path2[cnt] != 0 && BufferPosition<MTU )
+    {
+        txBuffer[BufferPosition++] = AprsSettings.Path2[cnt];
+        cnt++;
+    }
+    
+    txBuffer[BufferPosition++] = ':';
+    
+    cnt=0;
+    while ( payload[cnt] != 0 && BufferPosition<MTU )
+    {
+        txBuffer[BufferPosition++] = payload[cnt];
+        cnt++;
+    }
+    printf("%s\n", txBuffer);
+}
+
+void transmit() {
+  uint16_t position = 0;
+  
+  LoRa.beginPacket();
+  while( txBuffer[position] != 0 )
+  {
+    LoRa.write(txBuffer[position]);
+    position++;
+  }
+  LoRa.endPacket();
+
+  LoRa.receive();
 }