Diff: PCMessaging.h

Revision:

6:71da5b99de97

Parent:

5:2ce1be9d4bef

Child:

7:1bec23c68a3c

Child:

9:893481b2e488

--- a/PCMessaging.h	Sat May 04 23:43:53 2013 +0000
+++ b/PCMessaging.h	Sun May 05 14:35:25 2013 +0000
@@ -1,20 +1,20 @@
 //these are defines for the messages that are sent from the PC across the USB
 //these messages produce reactions on the mbed
-const unsigned char  STATUS_MSG         =0;
-const unsigned char  POSVEL_MSG         =1;
-const unsigned char  STARTDATA_MSG      =2;
-const unsigned char  STOPDATA_MSG       =3;
-const unsigned char  STARTSTREAM_MSG    =4;
-const unsigned char  STOPSTREAM_MSG     =5;
-const unsigned char  STARTLOGINFO_MSG   =6;
-const unsigned char  STOPLOGINFO_MSG    =7;
-const unsigned char  FIRE_TRIGGER_MSG   =8;
+const unsigned char  POSVEL_MSG         =0;
+const unsigned char  FIRE_TRIGGER_MSG   =1;
+const unsigned char  STATUS_MSG         =2;
+const unsigned char  STARTDATA_MSG      =3;
+const unsigned char  STOPDATA_MSG       =4;
+const unsigned char  STARTSTREAM_MSG    =5;
+const unsigned char  STOPSTREAM_MSG     =6;
+const unsigned char  STARTLOGINFO_MSG   =7;
+const unsigned char  STOPLOGINFO_MSG    =8;
 
 const double  DEGREES_TO_RADIANS = acos(-1.0)/180.0;
 const double eccen          = 0.0818191908426;  //WGS84 earth eccentricity
 const double earthRadius    = 6378137;          //WGS84 earthRadius in meters
 
-const unsigned short serBuffMax = 1024;
+const unsigned short serBuffMax = 18;
 char serBuf[serBuffMax];
 int serBufChars=0;
 
@@ -36,6 +36,9 @@
 unsigned char CR = 0x0d;                //ASCII Carriage Return
 unsigned char LF = 0x0a;                //ASCII Line Feed
 
+char preamble[5] = "WMsg";
+char testPreamble[5];
+
 void setUpMessages(void)
 { 
     //set up the ASCII text records that are candidates to be passed from the PC
@@ -50,40 +53,59 @@
     sprintf(msgList[FIRE_TRIGGER_MSG],  "WMsg TRIGGER");
     //message length is from 10 to 16 chars
     
-    toPC.printf(" finished setting up messages \n");
+ //   toPC.printf(" finished setting up messages \n");
 }
 
 void readFromPC()
 {
-     //The received commands only occur at the initialization stage -- time is not that critical there.
-    //during the real-time action, we will never pass the followong if test ( no characters received)
+    //  should this be a while rather than if ??? -- may have multiple bytes in buffer
     if (toPC.readable()) //read a PC serial byte and test it for a command
     {
-        
-        // Read in next character
+        // Read in next character  -- why not read all available??
         unsigned char inChar = 0;
-        if(toPC.readable() ) inChar = toPC.getc();  //read char from the USB serial link to the PC
+        inChar = toPC.getc();  //read char from the USB serial link to the PC
         //toPC.printf("%02x ",inChar);
         
         //incoming messages will end witb a CR / LF -- disregard these chars
         if (inChar == CR || inChar == LF)  return; //CR is a 0x0a
         
-        // serBuffMax = 1024 -- largest serBuffMax is 1023 -- but we add one below for the '\0'
-        if (serBufChars >= (serBuffMax-2)) {toPC.printf("WMsg overun char buff \n"); serBufChars = 0; };
-        serBuf[serBufChars] = inChar; //set this char in a char array
+        //all received messages assumed to have a WMsg preamble
+        //if we have read 4 chars, test these for "WMsg", if they are not WMsg, reset the buffer counter
+        //if we receive an occasional bad byte that messes up a message, this will resynch fast to a next message
+        //this will let us miss a message --- but hopefully only one
+        
+        // serBuffMax = 18 -- largest serBuffMax is 16 -- but we add one below for the '\0'
+        // if the following occurs we have had a trash byte following a WMsg header
+        if (serBufChars >= (serBuffMax-2)) {toPC.printf("WMsg restart message search\n"); serBufChars = 0; }
+        
+        serBuf[serBufChars] = inChar; //set this char in a char array for testing complete message
+  
+        testPreamble[serBufChars] = inChar;  //char array for testing the preamble
         serBufChars++;
         
+        if (serBufChars == 4)  //four initial chars detected (0, 1, 2, 3)
+        {
+            testPreamble[4] = '\0';  //form null-terminated string for compare
+            if (strncmp(testPreamble, preamble, 5) != 0)   //compare the chars to the WMsg preamble
+            {
+                toPC.printf("WMsg preamble mismatch \n");
+                serBufChars = 0;  //if they dont match -- restart the search for a preamble
+                return;
+            }
+        }
+        
+        //if we get here, we have found a preamble and we are looking for a complete message
         //no need to continue if numChars are less than the shortest candidate message
         if (serBufChars < minMessageSize) return;
                 
         // Append end of string
-        //We always assume we have a complete message string and test for this below
+        // We always assume we have a complete message string and test for this below
         serBuf[serBufChars] = '\0';
         
         bool validMessage = false;
         
-        
         // Check for valid message -- there are numMessages possible messages
+        //this assumes that the message buffer contains an exact message
         for (int m = 0; m < numMessages && !validMessage; m++) //check for all messages ... 
         {
             //toPC.printf(" \n\n found chars to test %3d %3d %s \n\n\n ", serBufChars, strlen(msgList[m]), serBuf );
@@ -99,7 +121,6 @@
                 validMessage = true;
                 serBufChars = 0; //reset the character count to reset for next message
                 
-    
                 //set programmatic action flags based on the message
                 switch(m)
                 {
@@ -130,11 +151,14 @@
                     break;  
                     case FIRE_TRIGGER_MSG:
                         fireTrigger = true;
+                        toPC.printf("MBED received trigger command \n");
                     break;
                 }  //end Switch statement
                 break;
             } //end test for a valid message
+            
         }  //end message text loop
+        
     }  //end pc.readable
 };
 
@@ -236,7 +260,7 @@
             //th file is closed(in main) if we dont receive POSVAL messages for 60 secs
             if (fpNav == NULL)
             { 
-                toPC.printf(" opening the SD card file \n");
+                toPC.printf("WMsg opening the SD card file \n");
                 fpNav = fopen("/sd/Data/NAV.bin", "wb");
                 wait_ms(10);
                 recordData = true;